Mercurial > hg > nginx-site
annotate xml/en/docs/dev/development_guide.xml @ 1920:de5251816480
Fixed a typo.
| author | Vladimir Homutov <vl@nginx.com> |
|---|---|
| date | Thu, 02 Mar 2017 13:12:01 +0300 |
| parents | dcfb4f3ac8a7 |
| children | 2c14a16c61eb |
| rev | line source |
|---|---|
| 1899 | 1 <?xml version="1.0"?> |
| 2 | |
| 3 <!-- | |
| 4 Copyright (C) Nginx, Inc. | |
| 5 --> | |
| 6 | |
| 7 <!DOCTYPE article SYSTEM "../../../../dtd/article.dtd"> | |
| 8 | |
| 9 <article name="Development guide" | |
| 10 link="/en/docs/dev/development_guide.html" | |
| 11 lang="en" | |
|
1914
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Vladimir Homutov <vl@nginx.com>
parents:
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changeset
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12 rev="2"> |
| 1899 | 13 |
| 14 <section name="Introduction" id="introduction"> | |
| 15 | |
| 16 | |
| 17 <section name="Code layout" id="code_layout"> | |
| 18 | |
| 19 <para> | |
| 20 <list type="bullet"> | |
| 21 <listitem> | |
| 22 <literal>auto</literal> - build scripts | |
| 23 </listitem> | |
| 24 | |
| 25 <listitem> | |
| 26 <literal>src</literal> | |
| 27 | |
| 28 <list type="bullet"> | |
| 29 | |
| 30 <listitem> | |
| 31 <literal>core</literal> - basic types and functions - string, array, log, | |
| 32 pool etc | |
| 33 </listitem> | |
| 34 | |
| 35 <listitem> | |
| 36 <literal>event</literal> - event core | |
| 37 | |
| 38 <list type="bullet"> | |
| 39 | |
| 40 <listitem> | |
| 41 <literal>modules</literal> - event notification modules: epoll, kqueue, | |
| 42 select etc | |
| 43 </listitem> | |
| 44 | |
| 45 </list> | |
| 46 | |
| 47 </listitem> | |
| 48 | |
| 49 <listitem> | |
| 50 <literal>http</literal> - core HTTP module and common code | |
| 51 | |
| 52 <list type="bullet"> | |
| 53 | |
| 54 <listitem> | |
| 55 <literal>modules</literal> - other HTTP modules | |
| 56 </listitem> | |
| 57 | |
| 58 <listitem> | |
| 59 <literal>v2</literal> - HTTPv2 | |
| 60 </listitem> | |
| 61 | |
| 62 </list> | |
| 63 | |
| 64 </listitem> | |
| 65 | |
| 66 <listitem> | |
| 67 <literal>mail</literal> - mail modules | |
| 68 </listitem> | |
| 69 | |
| 70 <listitem> | |
| 71 <literal>os</literal> - platform-specific code | |
| 72 | |
| 73 <list type="bullet"> | |
| 74 | |
| 75 <listitem> | |
| 76 <literal>unix</literal> | |
| 77 </listitem> | |
| 78 | |
| 79 <listitem> | |
| 80 <literal>win32</literal> | |
| 81 </listitem> | |
| 82 | |
| 83 </list> | |
| 84 | |
| 85 </listitem> | |
| 86 | |
| 87 <listitem> | |
| 88 <literal>stream</literal> - stream modules | |
| 89 </listitem> | |
| 90 | |
| 91 </list> | |
| 92 | |
| 93 </listitem> | |
| 94 | |
| 95 </list> | |
| 96 </para> | |
| 97 | |
| 98 </section> | |
| 99 | |
| 100 | |
| 101 <section name="Include files" id="include_files"> | |
| 102 | |
| 103 <para> | |
| 104 Each nginx file should start with including the following two files: | |
| 105 </para> | |
| 106 | |
| 107 | |
| 108 <programlisting> | |
| 109 #include <ngx_config.h> | |
| 110 #include <ngx_core.h> | |
| 111 </programlisting> | |
| 112 | |
| 113 <para> | |
| 114 In addition to that, HTTP code should include | |
| 115 </para> | |
| 116 | |
| 117 | |
| 118 <programlisting> | |
| 119 #include <ngx_http.h> | |
| 120 </programlisting> | |
| 121 | |
| 122 <para> | |
| 123 Mail code should include | |
| 124 </para> | |
| 125 | |
| 126 | |
| 127 <programlisting> | |
| 128 #include <ngx_mail.h> | |
| 129 </programlisting> | |
| 130 | |
| 131 <para> | |
| 132 Stream code should include | |
| 133 </para> | |
| 134 | |
| 135 | |
| 136 <programlisting> | |
| 137 #include <ngx_stream.h> | |
| 138 </programlisting> | |
| 139 | |
| 140 </section> | |
| 141 | |
| 142 | |
| 143 <section name="Integers" id="integers"> | |
| 144 | |
| 145 <para> | |
| 146 For general purpose, nginx code uses the following two integer types | |
| 147 <literal>ngx_int_t</literal> and <literal>ngx_uint_t</literal> which are | |
| 148 typedefs for <literal>intptr_t</literal> and <literal>uintptr_t</literal>. | |
| 149 </para> | |
| 150 | |
| 151 </section> | |
| 152 | |
| 153 | |
| 154 <section name="Common return codes" id="common_return_codes"> | |
| 155 | |
| 156 <para> | |
| 157 Most functions in nginx return the following codes: | |
| 158 </para> | |
| 159 | |
| 160 <para> | |
| 161 <list type="bullet"> | |
| 162 | |
| 163 <listitem> | |
| 164 <literal>NGX_OK</literal> - operation succeeded | |
| 165 </listitem> | |
| 166 | |
| 167 <listitem> | |
| 168 <literal>NGX_ERROR</literal> - operation failed | |
| 169 </listitem> | |
| 170 | |
| 171 <listitem> | |
| 172 <literal>NGX_AGAIN</literal> - operation incomplete, function should be called | |
| 173 again | |
| 174 </listitem> | |
| 175 | |
| 176 <listitem> | |
| 177 <literal>NGX_DECLINED</literal> - operation rejected, for example, if disabled | |
| 178 in configuration. This is never an error | |
| 179 </listitem> | |
| 180 | |
| 181 <listitem> | |
| 182 <literal>NGX_BUSY</literal> - resource is not available | |
| 183 </listitem> | |
| 184 | |
| 185 <listitem> | |
| 186 <literal>NGX_DONE</literal> - operation done or continued elsewhere. | |
| 187 Also used as an alternative success code | |
| 188 </listitem> | |
| 189 | |
| 190 <listitem> | |
| 191 <literal>NGX_ABORT</literal> - function was aborted. | |
| 192 Also used as an alternative error code | |
| 193 </listitem> | |
| 194 | |
| 195 </list> | |
| 196 </para> | |
| 197 | |
| 198 </section> | |
| 199 | |
| 200 | |
| 201 <section name="Error handling" id="error_handling"> | |
| 202 | |
| 203 <para> | |
| 204 For getting the last system error code, the <literal>ngx_errno</literal> macro | |
| 205 is available. | |
| 206 It's mapped to <literal>errno</literal> on POSIX platforms and to | |
| 207 <literal>GetLastError()</literal> call in Windows. | |
| 208 For getting the last socket error number, the | |
| 209 <literal>ngx_socket_errno</literal> macro is available. | |
| 210 It's mapped to <literal>errno</literal> on POSIX systems as well, | |
| 211 and to <literal>WSAGetLastError()</literal> call on Windows. | |
| 212 For performance reasons the values of <literal>ngx_errno</literal> or | |
| 213 <literal>ngx_socket_errno</literal> should not be accessed more than | |
| 214 once in a row. | |
| 215 The error value should be stored in a local variable of type | |
| 216 <literal>ngx_err_t</literal> for using multiple times, if required. | |
| 217 For setting errors, <literal>ngx_set_errno(errno)</literal> and | |
| 218 <literal>ngx_set_socket_errno(errno)</literal> macros are available. | |
| 219 </para> | |
| 220 | |
| 221 <para> | |
| 222 The values of <literal>ngx_errno</literal> or | |
| 223 <literal>ngx_socket_errno</literal> can be passed to logging functions | |
| 224 <literal>ngx_log_error()</literal> and <literal>ngx_log_debugX()</literal>, in | |
| 225 which case system error text is added to the log message. | |
| 226 </para> | |
| 227 | |
| 228 <para> | |
| 229 Example using <literal>ngx_errno</literal>: | |
| 230 </para> | |
| 231 | |
| 232 | |
| 233 <programlisting> | |
| 234 void | |
| 235 ngx_my_kill(ngx_pid_t pid, ngx_log_t *log, int signo) | |
| 236 { | |
| 237 ngx_err_t err; | |
| 238 | |
| 239 if (kill(pid, signo) == -1) { | |
| 240 err = ngx_errno; | |
| 241 | |
| 242 ngx_log_error(NGX_LOG_ALERT, log, err, "kill(%P, %d) failed", pid, signo); | |
| 243 | |
| 244 if (err == NGX_ESRCH) { | |
| 245 return 2; | |
| 246 } | |
| 247 | |
| 248 return 1; | |
| 249 } | |
| 250 | |
| 251 return 0; | |
| 252 } | |
| 253 </programlisting> | |
| 254 | |
| 255 </section> | |
| 256 | |
| 257 | |
| 258 </section> | |
| 259 | |
| 260 | |
| 261 <section name="Strings" id="strings"> | |
| 262 | |
| 263 | |
| 264 <section name="Overview" id="overview"> | |
| 265 | |
| 266 <para> | |
| 267 For C strings, nginx code uses unsigned character type pointer | |
| 268 <literal>u_char *</literal>. | |
| 269 </para> | |
| 270 | |
| 271 <para> | |
| 272 The nginx string type <literal>ngx_str_t</literal> is defined as follows: | |
| 273 </para> | |
| 274 | |
| 275 | |
| 276 <programlisting> | |
| 277 typedef struct { | |
| 278 size_t len; | |
| 279 u_char *data; | |
| 280 } ngx_str_t; | |
| 281 </programlisting> | |
| 282 | |
| 283 <para> | |
| 284 The <literal>len</literal> field holds the string length, | |
| 285 <literal>data</literal> holds the string data. | |
| 286 The string, held in <literal>ngx_str_t</literal>, may or may not be | |
| 287 null-terminated after the <literal>len</literal> bytes. | |
| 288 In most cases it’s not. | |
| 289 However, in certain parts of code (for example, when parsing configuration), | |
| 290 <literal>ngx_str_t</literal> objects are known to be null-terminated, and that | |
| 291 knowledge is used to simplify string comparison and makes it easier to pass | |
| 292 those strings to syscalls. | |
| 293 </para> | |
| 294 | |
| 295 <para> | |
| 296 A number of string operations are provided in nginx. | |
|
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297 They are declared in <path>src/core/ngx_string.h</path>. |
| 1899 | 298 Some of them are wrappers around standard C functions: |
| 299 </para> | |
| 300 | |
| 301 <para> | |
| 302 <list type="bullet"> | |
| 303 | |
| 304 <listitem> | |
| 305 <literal>ngx_strcmp()</literal> | |
| 306 </listitem> | |
| 307 | |
| 308 <listitem> | |
| 309 <literal>ngx_strncmp()</literal> | |
| 310 </listitem> | |
| 311 | |
| 312 <listitem> | |
| 313 <literal>ngx_strstr()</literal> | |
| 314 </listitem> | |
| 315 | |
| 316 <listitem> | |
| 317 <literal>ngx_strlen()</literal> | |
| 318 </listitem> | |
| 319 | |
| 320 <listitem> | |
| 321 <literal>ngx_strchr()</literal> | |
| 322 </listitem> | |
| 323 | |
| 324 <listitem> | |
| 325 <literal>ngx_memcmp()</literal> | |
| 326 </listitem> | |
| 327 | |
| 328 <listitem> | |
| 329 <literal>ngx_memset()</literal> | |
| 330 </listitem> | |
| 331 | |
| 332 <listitem> | |
| 333 <literal>ngx_memcpy()</literal> | |
| 334 </listitem> | |
| 335 | |
| 336 <listitem> | |
| 337 <literal>ngx_memmove()</literal> | |
| 338 </listitem> | |
| 339 | |
| 340 </list> | |
| 341 | |
| 342 </para> | |
| 343 | |
| 344 <para> | |
| 345 Some nginx-specific string functions: | |
| 346 </para> | |
| 347 | |
| 348 <para> | |
| 349 <list type="bullet"> | |
| 350 | |
| 351 <listitem> | |
| 352 <literal>ngx_memzero()</literal> fills memory with zeroes | |
| 353 </listitem> | |
| 354 | |
| 355 <listitem> | |
| 356 <literal>ngx_cpymem()</literal> does the same as | |
| 357 <literal>ngx_memcpy()</literal>, but returns the final destination address | |
| 358 This one is handy for appending multiple strings in a row | |
| 359 </listitem> | |
| 360 | |
| 361 <listitem> | |
| 362 <literal>ngx_movemem()</literal> does the same as | |
| 363 <literal>ngx_memmove()</literal>, but returns the final destination address. | |
| 364 </listitem> | |
| 365 | |
| 366 <listitem> | |
| 367 <literal>ngx_strlchr()</literal> searches for a character in a string, | |
| 368 delimited by two pointers | |
| 369 </listitem> | |
| 370 </list> | |
| 371 </para> | |
| 372 | |
| 373 <para> | |
| 374 Some case conversion and comparison functions: | |
| 375 </para> | |
| 376 | |
| 377 <para> | |
| 378 <list type="bullet"> | |
| 379 | |
| 380 <listitem> | |
| 381 <literal>ngx_tolower()</literal> | |
| 382 </listitem> | |
| 383 | |
| 384 <listitem> | |
| 385 <literal>ngx_toupper()</literal> | |
| 386 </listitem> | |
| 387 | |
| 388 <listitem> | |
| 389 <literal>ngx_strlow()</literal> | |
| 390 </listitem> | |
| 391 | |
| 392 <listitem> | |
| 393 <literal>ngx_strcasecmp()</literal> | |
| 394 </listitem> | |
| 395 | |
| 396 <listitem> | |
| 397 <literal>ngx_strncasecmp()</literal> | |
| 398 </listitem> | |
| 399 | |
| 400 </list> | |
| 401 </para> | |
| 402 | |
| 403 </section> | |
| 404 | |
| 405 | |
| 406 <section name="Formatting" id="formatting"> | |
| 407 | |
| 408 <para> | |
| 409 A number of formatting functions are provided by nginx. These functions support nginx-specific types: | |
| 410 </para> | |
| 411 | |
| 412 | |
| 413 <para> | |
| 414 <list type="bullet"> | |
| 415 | |
| 416 <listitem> | |
| 417 <literal>ngx_sprintf(buf, fmt, ...)</literal> | |
| 418 </listitem> | |
| 419 | |
| 420 <listitem> | |
| 421 <literal>ngx_snprintf(buf, max, fmt, ...)</literal> | |
| 422 </listitem> | |
| 423 | |
| 424 <listitem> | |
| 425 <literal>ngx_slrintf(buf, last, fmt, ...)</literal> | |
| 426 </listitem> | |
| 427 | |
| 428 <listitem> | |
| 429 <literal>ngx_vslprint(buf, last, fmt, args)</literal> | |
| 430 </listitem> | |
| 431 | |
| 432 <listitem> | |
| 433 <literal>ngx_vsnprint(buf, max, fmt, args)</literal> | |
| 434 </listitem> | |
| 435 | |
| 436 </list> | |
| 437 </para> | |
| 438 | |
| 439 <para> | |
| 440 The full list of formatting options, supported by these functions, can be found | |
|
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diff
changeset
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441 in <path>src/core/ngx_string.c</path>. Some of them are: |
| 1899 | 442 </para> |
| 443 | |
| 444 | |
| 445 <programlisting> | |
| 446 %O - off_t | |
| 447 %T - time_t | |
| 448 %z - size_t | |
| 449 %i - ngx_int_t | |
| 450 %p - void * | |
| 451 %V - ngx_str_t * | |
| 452 %s - u_char * (null-terminated) | |
| 453 %*s - size_t + u_char * | |
| 454 </programlisting> | |
| 455 | |
| 456 <para> | |
| 457 The ‘u’ modifier makes most types unsigned, ‘X’/‘x’ convert output to hex. | |
| 458 </para> | |
| 459 | |
| 460 <para> | |
| 461 Example: | |
| 462 | |
| 463 <programlisting> | |
| 464 u_char buf[NGX_INT_T_LEN]; | |
| 465 size_t len; | |
| 466 ngx_int_t n; | |
| 467 | |
| 468 /* set n here */ | |
| 469 | |
| 470 len = ngx_sprintf(buf, "%ui", n) - buf; | |
| 471 </programlisting> | |
| 472 | |
| 473 </para> | |
| 474 | |
| 475 </section> | |
| 476 | |
| 477 | |
| 478 <section name="Numeric conversion" id="numeric_conversion"> | |
| 479 | |
| 480 <para> | |
| 481 Several functions for numeric conversion are implemented in nginx: | |
| 482 </para> | |
| 483 | |
| 484 <para> | |
| 485 <list type="bullet"> | |
| 486 | |
| 487 <listitem> | |
| 488 <literal>ngx_atoi(line, n)</literal> - converts a string of given length to a | |
| 489 positive integer of type <literal>ngx_int_t</literal>. | |
| 490 Returns <literal>NGX_ERROR</literal> on error | |
| 491 </listitem> | |
| 492 | |
| 493 <listitem> | |
| 494 <literal>ngx_atosz(line, n)</literal> - same for <literal>ssize_t</literal> | |
| 495 type | |
| 496 </listitem> | |
| 497 | |
| 498 <listitem> | |
| 499 <literal>ngx_atoof(line, n)</literal> - same for <literal>off_t</literal> | |
| 500 type | |
| 501 </listitem> | |
| 502 | |
| 503 <listitem> | |
| 504 <literal>ngx_atotm(line, n)</literal> - same for <literal>time_t</literal> | |
| 505 type | |
| 506 </listitem> | |
| 507 | |
| 508 <listitem> | |
| 509 <literal>ngx_atofp(line, n, point)</literal> - converts a fixed point floating | |
| 510 number of given length to a positive integer of type | |
| 511 <literal>ngx_int_t</literal>. | |
| 512 The result is shifted left by <literal>points</literal> decimal | |
| 513 positions. The string representation of the number is expected to have no more | |
| 514 than <literal>points</literal> fractional digits. | |
| 515 Returns <literal>NGX_ERROR</literal> on error. For example, | |
| 516 <literal>ngx_atofp("10.5", 4, 2)</literal> returns <literal>1050</literal> | |
| 517 </listitem> | |
| 518 | |
| 519 <listitem> | |
| 520 <literal>ngx_hextoi(line, n)</literal> - converts hexadecimal representation of | |
| 521 a positive integer to <literal>ngx_int_t</literal>. Returns | |
| 522 <literal>NGX_ERROR</literal> on error | |
| 523 </listitem> | |
| 524 | |
| 525 </list> | |
| 526 </para> | |
| 527 | |
| 528 </section> | |
| 529 | |
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530 <section name="Regular expressions" id="regex"> |
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531 |
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532 <para> |
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533 The regular expressions interface in nginx is a wrapper around |
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534 the <link url="http://www.pcre.org">PCRE</link> |
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535 library. |
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536 The corresponding header file is <path>src/core/ngx_regex.h</path>. |
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537 </para> |
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538 |
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539 <para> |
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parents:
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540 To use a regular expression for string matching, first, it needs to be |
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parents:
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541 compiled, this is usually done at configuration phase. |
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parents:
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542 Note that since PCRE support is optional, all code using the interface must |
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Added the "Regular expressions" section to the development guide.
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parents:
1915
diff
changeset
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543 be protected by the surrounding <literal>NGX_PCRE</literal> macro: |
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parents:
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544 <programlisting> |
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545 #if (NGX_PCRE) |
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546 ngx_regex_t *re; |
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parents:
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547 ngx_regex_compile_t rc; |
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parents:
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548 |
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parents:
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diff
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549 u_char errstr[NGX_MAX_CONF_ERRSTR]; |
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parents:
1915
diff
changeset
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550 |
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Added the "Regular expressions" section to the development guide.
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parents:
1915
diff
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551 ngx_str_t value = ngx_string("message (\\d\\d\\d).*Codeword is '(?<cw>\\w+)'"); |
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dcfb4f3ac8a7
Added the "Regular expressions" section to the development guide.
Vladimir Homutov <vl@nginx.com>
parents:
1915
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552 |
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553 ngx_memzero(&rc, sizeof(ngx_regex_compile_t)); |
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554 |
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555 rc.pattern = value; |
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556 rc.pool = cf->pool; |
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557 rc.err.len = NGX_MAX_CONF_ERRSTR; |
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558 rc.err.data = errstr; |
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559 /* rc.options are passed as is to pcre_compile() */ |
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560 |
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561 if (ngx_regex_compile(&rc) != NGX_OK) { |
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562 ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "%V", &rc.err); |
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563 return NGX_CONF_ERROR; |
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564 } |
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565 |
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566 re = rc.regex; |
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567 #endif |
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568 </programlisting> |
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569 After successful compilation, <literal>ngx_regex_compile_t</literal> structure |
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570 fields <literal>captures</literal> and <literal>named_captures</literal> |
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571 are filled with count of all and named captures respectively found in the |
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572 regular expression. |
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573 </para> |
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574 |
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575 <para> |
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576 Later, the compiled regular expression may be used to match strings against it: |
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577 <programlisting> |
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578 ngx_int_t n; |
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579 int captures[(1 + rc.captures) * 3]; |
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580 |
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581 ngx_str_t input = ngx_string("This is message 123. Codeword is 'foobar'."); |
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582 |
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583 n = ngx_regex_exec(re, &input, captures, (1 + rc.captures) * 3); |
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584 if (n >= 0) { |
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585 /* string matches expression */ |
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586 |
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587 } else if (n == NGX_REGEX_NO_MATCHED) { |
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588 /* no match was found */ |
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589 |
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590 } else { |
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591 /* some error */ |
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592 ngx_log_error(NGX_LOG_ALERT, log, 0, ngx_regex_exec_n " failed: %i", n); |
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593 } |
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594 </programlisting> |
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595 The arguments of <literal>ngx_regex_exec()</literal> are: the compiled regular |
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596 expression <literal>re</literal>, string to match <literal>s</literal>, |
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597 optional array of integers to hold found <literal>captures</literal> |
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598 and its <literal>size</literal>. |
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599 The <literal>captures</literal> array size must be a multiple of three, |
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600 per requirements of the |
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601 <link url="http://www.pcre.org/original/doc/html/pcreapi.html">PCRE API</link>. |
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602 In the example, its size is calculated from a total number of captures plus |
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603 one for the matched string itself. |
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604 </para> |
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605 |
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606 <para> |
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607 Now, if there are matches, captures may be accessed: |
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608 <programlisting> |
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609 u_char *p; |
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610 size_t size; |
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611 ngx_str_t name, value; |
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612 |
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613 /* all captures */ |
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614 for (i = 0; i < n * 2; i += 2) { |
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615 value.data = input.data + captures[i]; |
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616 value.len = captures[i + 1] - captures[i]; |
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617 } |
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618 |
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619 /* accessing named captures */ |
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620 |
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621 size = rc.name_size; |
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622 p = rc.names; |
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623 |
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624 for (i = 0; i < rc.named_captures; i++, p += size) { |
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625 |
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626 /* capture name */ |
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627 name.data = &p[2]; |
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628 name.len = ngx_strlen(name.data); |
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629 |
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630 n = 2 * ((p[0] << 8) + p[1]); |
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631 |
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632 /* captured value */ |
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633 value.data = &input.data[captures[n]]; |
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634 value.len = captures[n + 1] - captures[n]; |
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635 } |
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636 </programlisting> |
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637 </para> |
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638 |
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639 <para> |
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640 The <literal>ngx_regex_exec_array()</literal> function accepts the array of |
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641 <literal>ngx_regex_elt_t</literal> elements (which are just compiled regular |
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642 expressions with associated names), a string to match and a log. |
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643 The function will apply expressions from the array to the string until |
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644 the match is found or no more expressions are left. |
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645 The return value is <literal>NGX_OK</literal> in case of match and |
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646 <literal>NGX_DECLINED</literal> otherwise, or <literal>NGX_ERROR</literal> |
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647 in case of error. |
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648 </para> |
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649 |
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650 </section> |
| 1899 | 651 |
| 652 </section> | |
| 653 | |
| 654 | |
| 655 <section name="Containers" id="containers"> | |
| 656 | |
| 657 | |
| 658 <section name="Array" id="array"> | |
| 659 | |
| 660 <para> | |
| 661 The nginx array type <literal>ngx_array_t</literal> is defined as follows | |
| 662 </para> | |
| 663 | |
| 664 | |
| 665 <programlisting> | |
| 666 typedef struct { | |
| 667 void *elts; | |
| 668 ngx_uint_t nelts; | |
| 669 size_t size; | |
| 670 ngx_uint_t nalloc; | |
| 671 ngx_pool_t *pool; | |
| 672 } ngx_array_t; | |
| 673 </programlisting> | |
| 674 | |
| 675 <para> | |
| 676 The elements of array are available through the <literal>elts</literal> field. | |
| 677 The number of elements is held in the <literal>nelts</literal> field. | |
| 678 The <literal>size</literal> field holds the size of a single element and is set | |
| 679 when initializing the array. | |
| 680 </para> | |
| 681 | |
| 682 <para> | |
| 683 An array can be created in a pool with the | |
| 684 <literal>ngx_array_create(pool, n, size)</literal> call. | |
| 685 An already allocated array object can be initialized with the | |
| 686 <literal>ngx_array_init(array, pool, n, size)</literal> call. | |
| 687 </para> | |
| 688 | |
| 689 | |
| 690 <programlisting> | |
| 691 ngx_array_t *a, b; | |
| 692 | |
| 693 /* create an array of strings with preallocated memory for 10 elements */ | |
| 694 a = ngx_array_create(pool, 10, sizeof(ngx_str_t)); | |
| 695 | |
| 696 /* initialize string array for 10 elements */ | |
| 697 ngx_array_init(&b, pool, 10, sizeof(ngx_str_t)); | |
| 698 </programlisting> | |
| 699 | |
| 700 <para> | |
| 701 Adding elements to array are done with the following functions: | |
| 702 </para> | |
| 703 | |
| 704 <para> | |
| 705 <list type="bullet"> | |
| 706 | |
| 707 <listitem> | |
| 708 <literal>ngx_array_push(a)</literal> adds one tail element and returns pointer | |
| 709 to it | |
| 710 </listitem> | |
| 711 | |
| 712 <listitem> | |
| 713 <literal>ngx_array_push_n(a, n)</literal> adds <literal>n</literal> tail elements | |
| 714 and returns pointer to the first one | |
| 715 </listitem> | |
| 716 | |
| 717 </list> | |
| 718 </para> | |
| 719 | |
| 720 <para> | |
| 721 If currently allocated memory is not enough for new elements, a new memory for | |
| 722 elements is allocated and existing elements are copied to that memory. | |
| 723 The new memory block is normally twice as large, as the existing one. | |
| 724 </para> | |
| 725 | |
| 726 | |
| 727 <programlisting> | |
| 728 s = ngx_array_push(a); | |
| 729 ss = ngx_array_push_n(&b, 3); | |
| 730 </programlisting> | |
| 731 | |
| 732 </section> | |
| 733 | |
| 734 | |
| 735 <section name="List" id="list"> | |
| 736 | |
| 737 <para> | |
| 738 List in nginx is a sequence of arrays, optimized for inserting a potentially | |
| 739 large number of items. The list type is defined as follows: | |
| 740 </para> | |
| 741 | |
| 742 | |
| 743 <programlisting> | |
| 744 typedef struct { | |
| 745 ngx_list_part_t *last; | |
| 746 ngx_list_part_t part; | |
| 747 size_t size; | |
| 748 ngx_uint_t nalloc; | |
| 749 ngx_pool_t *pool; | |
| 750 } ngx_list_t; | |
| 751 </programlisting> | |
| 752 | |
| 753 <para> | |
| 754 The actual items are store in list parts, defined as follows: | |
| 755 </para> | |
| 756 | |
| 757 | |
| 758 <programlisting> | |
| 759 typedef struct ngx_list_part_s ngx_list_part_t; | |
| 760 | |
| 761 struct ngx_list_part_s { | |
| 762 void *elts; | |
| 763 ngx_uint_t nelts; | |
| 764 ngx_list_part_t *next; | |
| 765 }; | |
| 766 </programlisting> | |
| 767 | |
| 768 <para> | |
| 769 Initially, a list must be initialized by calling | |
| 770 <literal>ngx_list_init(list, pool, n, size)</literal> or created by calling | |
| 771 <literal>ngx_list_create(pool, n, size)</literal>. | |
| 772 Both functions receive the size of a single item and a number of items per list | |
| 773 part. | |
| 774 The <literal>ngx_list_push(list)</literal> function is used to add an item to the | |
| 775 list. Iterating over the items is done by direct accessing the list fields, as | |
| 776 seen in the example: | |
| 777 </para> | |
| 778 | |
| 779 | |
| 780 <programlisting> | |
| 781 ngx_str_t *v; | |
| 782 ngx_uint_t i; | |
| 783 ngx_list_t *list; | |
| 784 ngx_list_part_t *part; | |
| 785 | |
| 786 list = ngx_list_create(pool, 100, sizeof(ngx_str_t)); | |
| 787 if (list == NULL) { /* error */ } | |
| 788 | |
| 789 /* add items to the list */ | |
| 790 | |
| 791 v = ngx_list_push(list); | |
| 792 if (v == NULL) { /* error */ } | |
| 793 ngx_str_set(v, “foo”); | |
| 794 | |
| 795 v = ngx_list_push(list); | |
| 796 if (v == NULL) { /* error */ } | |
| 797 ngx_str_set(v, “bar”); | |
| 798 | |
| 799 /* iterate over the list */ | |
| 800 | |
| 801 part = &list->part; | |
| 802 v = part->elts; | |
| 803 | |
| 804 for (i = 0; /* void */; i++) { | |
| 805 | |
| 806 if (i >= part->nelts) { | |
| 807 if (part->next == NULL) { | |
| 808 break; | |
| 809 } | |
| 810 | |
| 811 part = part->next; | |
| 812 v = part->elts; | |
| 813 i = 0; | |
| 814 } | |
| 815 | |
| 816 ngx_do_smth(&v[i]); | |
| 817 } | |
| 818 </programlisting> | |
| 819 | |
| 820 <para> | |
| 821 The primary use for the list in nginx is HTTP input and output headers. | |
| 822 </para> | |
| 823 | |
| 824 <para> | |
| 825 The list does not support item removal. | |
| 826 However, when needed, items can internally be marked as missing without actual | |
| 827 removing from the list. | |
| 828 For example, HTTP output headers which are stored as | |
| 829 <literal>ngx_table_elt_t</literal> objects, are marked as missing by setting | |
| 830 the <literal>hash</literal> field of <literal>ngx_table_elt_t</literal> to | |
| 831 zero. Such items are explicitly skipped, when iterating over the headers. | |
| 832 </para> | |
| 833 | |
| 834 </section> | |
| 835 | |
| 836 | |
| 837 <section name="Queue" id="queue"> | |
| 838 | |
| 839 <para> | |
| 840 Queue in nginx is an intrusive doubly linked list, with each node defined as | |
| 841 follows: | |
| 842 </para> | |
| 843 | |
| 844 | |
| 845 <programlisting> | |
| 846 typedef struct ngx_queue_s ngx_queue_t; | |
| 847 | |
| 848 struct ngx_queue_s { | |
| 849 ngx_queue_t *prev; | |
| 850 ngx_queue_t *next; | |
| 851 }; | |
| 852 </programlisting> | |
| 853 | |
| 854 <para> | |
| 855 The head queue node is not linked with any data. Before using, the list head | |
| 856 should be initialized with <literal>ngx_queue_init(q)</literal> call. | |
| 857 Queues support the following operations: | |
| 858 </para> | |
| 859 | |
| 860 <para> | |
| 861 <list type="bullet"> | |
| 862 | |
| 863 <listitem> | |
| 864 <literal>ngx_queue_insert_head(h, x)</literal>, | |
| 865 <literal>ngx_queue_insert_tail(h, x)</literal> - insert a new node | |
| 866 </listitem> | |
| 867 | |
| 868 <listitem> | |
| 869 <literal>ngx_queue_remove(x)</literal> - remove a queue node | |
| 870 </listitem> | |
| 871 | |
| 872 <listitem> | |
| 873 <literal>ngx_queue_split(h, q, n)</literal> - split a queue at a node, | |
| 874 queue tail is returned in a separate queue | |
| 875 </listitem> | |
| 876 | |
| 877 <listitem> | |
| 878 <literal>ngx_queue_add(h, n)</literal> - add second queue to the first queue | |
| 879 </listitem> | |
| 880 | |
| 881 <listitem> | |
| 882 <literal>ngx_queue_head(h)</literal>, | |
| 883 <literal>ngx_queue_last(h)</literal> - get first or last queue node | |
| 884 </listitem> | |
| 885 | |
| 886 <listitem> | |
| 887 <literal>ngx_queue_sentinel(h)</literal> | |
| 888 - get a queue sentinel object to end iteration at | |
| 889 </listitem> | |
| 890 | |
| 891 <listitem> | |
| 892 <literal>ngx_queue_data(q, type, link)</literal> - get reference to the beginning of a | |
| 893 queue node data structure, considering the queue field offset in it | |
| 894 </listitem> | |
| 895 | |
| 896 </list> | |
| 897 </para> | |
| 898 | |
| 899 <para> | |
| 900 Example: | |
| 901 </para> | |
| 902 | |
| 903 | |
| 904 <programlisting> | |
| 905 typedef struct { | |
| 906 ngx_str_t value; | |
| 907 ngx_queue_t queue; | |
| 908 } ngx_foo_t; | |
| 909 | |
| 910 ngx_foo_t *f; | |
| 911 ngx_queue_t values; | |
| 912 | |
| 913 ngx_queue_init(&values); | |
| 914 | |
| 915 f = ngx_palloc(pool, sizeof(ngx_foo_t)); | |
| 916 if (f == NULL) { /* error */ } | |
| 917 ngx_str_set(&f->value, “foo”); | |
| 918 | |
| 919 ngx_queue_insert_tail(&values, f); | |
| 920 | |
| 921 /* insert more nodes here */ | |
| 922 | |
| 923 for (q = ngx_queue_head(&values); | |
| 924 q != ngx_queue_sentinel(&values); | |
| 925 q = ngx_queue_next(q)) | |
| 926 { | |
| 927 f = ngx_queue_data(q, ngx_foo_t, queue); | |
| 928 | |
| 929 ngx_do_smth(&f->value); | |
| 930 } | |
| 931 </programlisting> | |
| 932 | |
| 933 </section> | |
| 934 | |
| 935 | |
| 936 <section name="Red-Black tree" id="red_black_tree"> | |
| 937 | |
| 938 <para> | |
|
1915
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939 The <path>src/core/ngx_rbtree.h</path> header file provides access to the |
| 1899 | 940 effective implementation of red-black trees. |
| 941 </para> | |
| 942 | |
| 943 | |
| 944 <programlisting> | |
| 945 typedef struct { | |
| 946 ngx_rbtree_t rbtree; | |
| 947 ngx_rbtree_node_t sentinel; | |
| 948 | |
| 949 /* custom per-tree data here */ | |
| 950 } my_tree_t; | |
| 951 | |
| 952 typedef struct { | |
| 953 ngx_rbtree_node_t rbnode; | |
| 954 | |
| 955 /* custom per-node data */ | |
| 956 foo_t val; | |
| 957 } my_node_t; | |
| 958 </programlisting> | |
| 959 | |
| 960 <para> | |
| 961 To deal with a tree as a whole, you need two nodes: root and sentinel. | |
| 962 Typically, they are added to some custom structure, thus allowing to | |
| 963 organize your data into a tree which leaves contain a link to or embed | |
| 964 your data. | |
| 965 </para> | |
| 966 | |
| 967 <para> | |
| 968 To initialize a tree: | |
| 969 </para> | |
| 970 | |
| 971 | |
| 972 <programlisting> | |
| 973 my_tree_t root; | |
| 974 | |
| 975 ngx_rbtree_init(&root.rbtree, &root.sentinel, insert_value_function); | |
| 976 </programlisting> | |
| 977 | |
| 978 <para> | |
| 979 The <literal>insert_value_function</literal> is a function that is | |
| 980 responsible for traversing the tree and inserting new values into correct | |
| 981 place. | |
| 982 For example, the <literal>ngx_str_rbtree_insert_value</literal> functions is | |
| 983 designed to deal with <literal>ngx_str_t</literal> type. | |
| 984 </para> | |
| 985 | |
| 986 | |
| 987 <programlisting> | |
| 988 void ngx_str_rbtree_insert_value(ngx_rbtree_node_t *temp, | |
| 989 ngx_rbtree_node_t *node, | |
| 990 ngx_rbtree_node_t *sentinel) | |
| 991 </programlisting> | |
| 992 | |
| 993 <para> | |
| 994 Its arguments are pointers to a root node of an insertion, newly created node | |
| 995 to be added, and a tree sentinel. | |
| 996 </para> | |
| 997 | |
| 998 <para> | |
| 999 The traversal is pretty straightforward and can be demonstrated with the | |
| 1000 following lookup function pattern: | |
| 1001 </para> | |
| 1002 | |
| 1003 | |
| 1004 <programlisting> | |
| 1005 my_node_t * | |
| 1006 my_rbtree_lookup(ngx_rbtree_t *rbtree, foo_t *val, uint32_t hash) | |
| 1007 { | |
| 1008 ngx_int_t rc; | |
| 1009 my_node_t *n; | |
| 1010 ngx_rbtree_node_t *node, *sentinel; | |
| 1011 | |
| 1012 node = rbtree->root; | |
| 1013 sentinel = rbtree->sentinel; | |
| 1014 | |
| 1015 while (node != sentinel) { | |
| 1016 | |
| 1017 n = (my_node_t *) node; | |
| 1018 | |
| 1019 if (hash != node->key) { | |
| 1020 node = (hash < node->key) ? node->left : node->right; | |
| 1021 continue; | |
| 1022 } | |
| 1023 | |
| 1024 rc = compare(val, node->val); | |
| 1025 | |
| 1026 if (rc < 0) { | |
| 1027 node = node->left; | |
| 1028 continue; | |
| 1029 } | |
| 1030 | |
| 1031 if (rc > 0) { | |
| 1032 node = node->right; | |
| 1033 continue; | |
| 1034 } | |
| 1035 | |
| 1036 return n; | |
| 1037 } | |
| 1038 | |
| 1039 return NULL; | |
| 1040 } | |
| 1041 </programlisting> | |
| 1042 | |
| 1043 <para> | |
| 1044 The <literal>compare()</literal> is a classic comparator function returning | |
| 1045 value less, equal or greater than zero. To speed up lookups and avoid comparing | |
| 1046 user objects that can be big, integer hash field is used. | |
| 1047 </para> | |
| 1048 | |
| 1049 <para> | |
| 1050 To add a node to a tree, allocate a new node, initialize it and call | |
| 1051 <literal>ngx_rbtree_insert()</literal>: | |
| 1052 </para> | |
| 1053 | |
| 1054 | |
| 1055 <programlisting> | |
| 1056 my_node_t *my_node; | |
| 1057 ngx_rbtree_node_t *node; | |
| 1058 | |
| 1059 my_node = ngx_palloc(...); | |
| 1060 init_custom_data(&my_node->val); | |
| 1061 | |
| 1062 node = &my_node->rbnode; | |
| 1063 node->key = create_key(my_node->val); | |
| 1064 | |
| 1065 ngx_rbtree_insert(&root->rbtree, node); | |
| 1066 </programlisting> | |
| 1067 | |
| 1068 <para> | |
| 1069 to remove a node: | |
| 1070 </para> | |
| 1071 | |
| 1072 | |
| 1073 <programlisting> | |
| 1074 ngx_rbtree_delete(&root->rbtree, node); | |
| 1075 </programlisting> | |
| 1076 | |
| 1077 </section> | |
| 1078 | |
|
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1079 <section name="Hash" id="hash"> |
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1080 |
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1081 <para> |
| 1920 | 1082 Hash table functions are declared in <path>src/core/ngx_hash.h</path>. |
|
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1083 Exact and wildcard matching is supported. |
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1084 The latter requires extra setup and is described in a separate section below. |
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1085 </para> |
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1086 |
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1087 <para> |
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1088 To initialize a hash, one needs to know the number of elements in advance, |
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1089 so that nginx can build the hash optimally. |
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1090 Two parameters that need to be configured are <literal>max_size</literal> |
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1091 and <literal>bucket_size</literal>. |
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1092 The details of setting up these are provided in a separate |
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1093 <link doc="../hash.xml">document</link>. |
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1094 Usually, these two parameters are configurable by user. |
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1095 Hash initialization settings are stored as the |
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1096 <literal>ngx_hash_init_t</literal> type, |
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1097 and the hash itself is <literal>ngx_hash_t</literal>: |
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1098 <programlisting> |
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1099 ngx_hash_t foo_hash; |
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1100 ngx_hash_init_t hash; |
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1101 |
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1102 hash.hash = &foo_hash; |
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1103 hash.key = ngx_hash_key; |
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1104 hash.max_size = 512; |
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1105 hash.bucket_size = ngx_align(64, ngx_cacheline_size); |
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1106 hash.name = "foo_hash"; |
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1107 hash.pool = cf->pool; |
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1108 hash.temp_pool = cf->temp_pool; |
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1109 </programlisting> |
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1110 The <literal>key</literal> is a pointer to a function that creates hash integer |
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1111 key from a string. |
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1112 Two generic functions are provided: |
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1113 <literal>ngx_hash_key(data, len)</literal> and |
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1114 <literal>ngx_hash_key_lc(data, len)</literal>. |
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1115 The latter converts a string to lowercase and thus requires the passed string to |
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1116 be writable. |
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1117 If this is not true, <literal>NGX_HASH_READONLY_KEY</literal> flag |
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1118 may be passed to the function, initializing array keys (see below). |
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1119 </para> |
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1120 |
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1121 <para> |
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1122 The hash keys are stored in <literal>ngx_hash_keys_arrays_t</literal> and |
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1123 are initialized with <literal>ngx_hash_keys_array_init(arr, type)</literal>: |
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1124 <programlisting> |
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1125 ngx_hash_keys_arrays_t foo_keys; |
|
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1126 |
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1127 foo_keys.pool = cf->pool; |
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1128 foo_keys.temp_pool = cf->temp_pool; |
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1129 |
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1130 ngx_hash_keys_array_init(&foo_keys, NGX_HASH_SMALL); |
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1131 </programlisting> |
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1132 The second parameter can be either <literal>NGX_HASH_SMALL</literal> or |
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1133 <literal>NGX_HASH_LARGE</literal> and controls the amount of preallocated |
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1134 resources for the hash. |
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1135 If you expect the hash to contain thousands elements, |
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1136 use <literal>NGX_HASH_LARGE</literal>. |
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1137 </para> |
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1138 |
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|
1139 <para> |
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1140 The <literal>ngx_hash_add_key(keys_array, key, value, flags)</literal> |
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1141 function is used to insert keys into hash keys array; |
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1142 <programlisting> |
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1143 ngx_str_t k1 = ngx_string("key1"); |
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1144 ngx_str_t k2 = ngx_string("key2"); |
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1145 |
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1146 ngx_hash_add_key(&foo_keys, &k1, &my_data_ptr_1, NGX_HASH_READONLY_KEY); |
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1147 ngx_hash_add_key(&foo_keys, &k2, &my_data_ptr_2, NGX_HASH_READONLY_KEY); |
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1148 </programlisting> |
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1149 </para> |
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1150 |
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|
1151 <para> |
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1152 Now, the hash table may be built using the call to |
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1153 <literal>ngx_hash_init(hinit, key_names, nelts)</literal>: |
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1154 |
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1155 <programlisting> |
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1156 ngx_hash_init(&hash, foo_keys.keys.elts, foo_keys.keys.nelts); |
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1157 </programlisting> |
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|
1158 |
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1159 This may fail, if <literal>max_size</literal> or <literal>bucket_size</literal> |
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|
1160 parameters are not big enough. |
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1161 When the hash is built, <literal>ngx_hash_find(hash, key, name, len)</literal> |
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1162 function may be used to look up elements: |
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|
1163 <programlisting> |
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|
1164 my_data_t *data; |
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1165 ngx_uint_t key; |
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1166 |
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1167 key = ngx_hash_key(k1.data, k1.len); |
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1168 |
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1169 data = ngx_hash_find(&foo_hash, key, k1.data, k1.len); |
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1170 if (data == NULL) { |
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1171 /* key not found */ |
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1172 } |
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|
1173 </programlisting> |
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|
1174 |
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|
1175 </para> |
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|
1176 |
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1177 <section name="Wildcard matching" id="wildcard_matching"> |
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1178 |
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|
1179 <para> |
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1180 To create a hash that works with wildcards, |
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1181 <literal>ngx_hash_combined_t</literal> type is used. |
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1182 It includes the hash type described above and has two additional keys arrays: |
|
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1183 <literal>dns_wc_head</literal> and <literal>dns_wc_tail</literal>. |
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1184 The initialization of basic properties is done similarly to a usual hash: |
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|
1185 <programlisting> |
|
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|
1186 ngx_hash_init_t hash |
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|
1187 ngx_hash_combined_t foo_hash; |
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|
1188 |
|
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1189 hash.hash = &foo_hash.hash; |
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1190 hash.key = ...; |
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1191 </programlisting> |
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|
1192 </para> |
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|
1193 |
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|
1194 <para> |
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1195 It is possible to add wildcard keys using the |
|
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|
1196 <literal>NGX_HASH_WILDCARD_KEY</literal> flag: |
|
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|
1197 <programlisting> |
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|
1198 /* k1 = ".example.org"; */ |
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1199 /* k2 = "foo.*"; */ |
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1200 ngx_hash_add_key(&foo_keys, &k1, &data1, NGX_HASH_WILDCARD_KEY); |
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1201 ngx_hash_add_key(&foo_keys, &k2, &data2, NGX_HASH_WILDCARD_KEY); |
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1202 </programlisting> |
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|
1203 The function recognizes wildcards and adds keys into corresponding arrays. |
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|
1204 Please refer to the |
|
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|
1205 <link doc="../http/ngx_http_map_module.xml" id="map"/> module |
|
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|
1206 documentation for the description of the wildcard syntax and |
|
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|
1207 matching algorithm. |
|
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|
1208 </para> |
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|
1209 |
|
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|
1210 <para> |
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1211 Depending on the contents of added keys, you may need to initialize up to three |
|
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|
1212 keys arrays: one for exact matching (described above), and two for matching |
|
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1213 starting from head or tail of a string: |
|
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|
1214 <programlisting> |
|
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1215 if (foo_keys.dns_wc_head.nelts) { |
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1216 |
|
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1217 ngx_qsort(foo_keys.dns_wc_head.elts, |
|
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1218 (size_t) foo_keys.dns_wc_head.nelts, |
|
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|
1219 sizeof(ngx_hash_key_t), |
|
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1220 cmp_dns_wildcards); |
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|
1221 |
|
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|
1222 hash.hash = NULL; |
|
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|
1223 hash.temp_pool = pool; |
|
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1224 |
|
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1225 if (ngx_hash_wildcard_init(&hash, foo_keys.dns_wc_head.elts, |
|
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1226 foo_keys.dns_wc_head.nelts) |
|
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|
1227 != NGX_OK) |
|
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|
1228 { |
|
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|
1229 return NGX_ERROR; |
|
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|
1230 } |
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|
1231 |
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|
1232 foo_hash.wc_head = (ngx_hash_wildcard_t *) hash.hash; |
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|
1233 } |
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|
1234 </programlisting> |
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|
1235 The keys array needs to be sorted, and initialization results must be added |
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1236 to the combined hash. |
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|
1237 The initialization of <literal>dns_wc_tail</literal> array is done similarly. |
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|
1238 </para> |
|
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|
1239 |
|
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|
1240 <para> |
|
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|
1241 The lookup in a combined hash is handled by the |
|
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|
1242 <literal>ngx_hash_find_combined(chash, key, name, len)</literal>: |
|
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1243 <programlisting> |
|
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|
1244 /* key = "bar.example.org"; - will match ".example.org" */ |
|
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|
1245 /* key = "foo.example.com"; - will match "foo.*" */ |
|
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1246 |
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1247 hkey = ngx_hash_key(key.data, key.len); |
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1248 res = ngx_hash_find_combined(&foo_hash, hkey, key.data, key.len); |
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1249 </programlisting> |
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1250 </para> |
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1251 |
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1252 </section> |
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1253 |
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1254 </section> |
| 1899 | 1255 |
| 1256 </section> | |
| 1257 | |
| 1258 | |
| 1259 <section name="Memory management" id="memory_management"> | |
| 1260 | |
| 1261 | |
| 1262 <section name="Heap" id="heap"> | |
| 1263 | |
| 1264 <para> | |
| 1265 To allocate memory from system heap, the following functions are provided by | |
| 1266 nginx: | |
| 1267 </para> | |
| 1268 | |
| 1269 <para> | |
| 1270 <list type="bullet"> | |
| 1271 | |
| 1272 <listitem> | |
| 1273 <literal>ngx_alloc(size, log)</literal> - allocate memory from system heap. | |
| 1274 This is a wrapper around <literal>malloc()</literal> with logging support. | |
| 1275 Allocation error and debugging information is logged to <literal>log</literal> | |
| 1276 </listitem> | |
| 1277 | |
| 1278 <listitem> | |
| 1279 <literal>ngx_calloc(size, log)</literal> - same as | |
| 1280 <literal>ngx_alloc()</literal>, but memory is filled with zeroes after | |
| 1281 allocation | |
| 1282 </listitem> | |
| 1283 | |
| 1284 <listitem> | |
| 1285 <literal>ngx_memalign(alignment, size, log)</literal> - allocate aligned memory | |
| 1286 from system heap. This is a wrapper around <literal>posix_memalign()</literal> | |
| 1287 on those platforms which provide it. | |
| 1288 Otherwise implementation falls back to <literal>ngx_alloc()</literal> which | |
| 1289 provides maximum alignment | |
| 1290 </listitem> | |
| 1291 | |
| 1292 <listitem> | |
| 1293 <literal>ngx_free(p)</literal> - free allocated memory. | |
| 1294 This is a wrapper around <literal>free()</literal> | |
| 1295 </listitem> | |
| 1296 | |
| 1297 </list> | |
| 1298 </para> | |
| 1299 | |
| 1300 </section> | |
| 1301 | |
| 1302 | |
| 1303 <section name="Pool" id="pool"> | |
| 1304 | |
| 1305 <para> | |
| 1306 Most nginx allocations are done in pools. Memory allocated in an nginx pool is | |
| 1307 freed automatically when the pool in destroyed. This provides good | |
| 1308 allocation performance and makes memory control easy. | |
| 1309 </para> | |
| 1310 | |
| 1311 <para> | |
| 1312 A pool internally allocates objects in continuous blocks of memory. Once a | |
| 1313 block is full, a new one is allocated and added to the pool memory | |
| 1314 block list. When a large allocation is requested which does not fit into | |
| 1315 a block, such allocation is forwarded to the system allocator and the | |
| 1316 returned pointer is stored in the pool for further deallocation. | |
| 1317 </para> | |
| 1318 | |
| 1319 <para> | |
| 1320 Nginx pool has the type <literal>ngx_pool_t</literal>. | |
| 1321 The following operations are supported: | |
| 1322 </para> | |
| 1323 | |
| 1324 <para> | |
| 1325 <list type="bullet"> | |
| 1326 | |
| 1327 <listitem> | |
| 1328 <literal>ngx_create_pool(size, log)</literal> - create a pool with given | |
| 1329 block size. The pool object returned is allocated in the pool as well. | |
| 1330 </listitem> | |
| 1331 | |
| 1332 <listitem> | |
| 1333 <literal>ngx_destroy_pool(pool)</literal> - free all pool memory, including | |
| 1334 the pool object itself. | |
| 1335 </listitem> | |
| 1336 | |
| 1337 <listitem> | |
| 1338 <literal>ngx_palloc(pool, size)</literal> - allocate aligned memory from pool | |
| 1339 </listitem> | |
| 1340 | |
| 1341 <listitem> | |
| 1342 <literal>ngx_pcalloc(pool, size)</literal> - allocated aligned memory | |
| 1343 from pool and fill it with zeroes | |
| 1344 </listitem> | |
| 1345 | |
| 1346 <listitem> | |
| 1347 <literal>ngx_pnalloc(pool, size)</literal> - allocate unaligned memory from pool. | |
| 1348 Mostly used for allocating strings | |
| 1349 </listitem> | |
| 1350 | |
| 1351 <listitem> | |
| 1352 <literal>ngx_pfree(pool, p)</literal> - free memory, previously allocated | |
| 1353 in the pool. | |
| 1354 Only allocations, forwarded to the system allocator, can be freed. | |
| 1355 </listitem> | |
| 1356 | |
| 1357 </list> | |
| 1358 </para> | |
| 1359 | |
| 1360 <programlisting> | |
| 1361 u_char *p; | |
| 1362 ngx_str_t *s; | |
| 1363 ngx_pool_t *pool; | |
| 1364 | |
| 1365 pool = ngx_create_pool(1024, log); | |
| 1366 if (pool == NULL) { /* error */ } | |
| 1367 | |
| 1368 s = ngx_palloc(pool, sizeof(ngx_str_t)); | |
| 1369 if (s == NULL) { /* error */ } | |
| 1370 ngx_str_set(s, “foo”); | |
| 1371 | |
| 1372 p = ngx_pnalloc(pool, 3); | |
| 1373 if (p == NULL) { /* error */ } | |
| 1374 ngx_memcpy(p, “foo”, 3); | |
| 1375 </programlisting> | |
| 1376 | |
| 1377 <para> | |
| 1378 Since chain links <literal>ngx_chain_t</literal> are actively used in nginx, | |
| 1379 nginx pool provides a way to reuse them. | |
| 1380 The <literal>chain</literal> field of <literal>ngx_pool_t</literal> keeps a | |
| 1381 list of previously allocated links ready for reuse. For efficient allocation of | |
| 1382 a chain link in a pool, the function | |
| 1383 <literal>ngx_alloc_chain_link(pool)</literal> should be used. | |
| 1384 This function looks up a free chain link in the pool list and only if it's | |
| 1385 empty allocates a new one. To free a link <literal>ngx_free_chain(pool, cl)</literal> | |
| 1386 should be called. | |
| 1387 </para> | |
| 1388 | |
| 1389 <para> | |
| 1390 Cleanup handlers can be registered in a pool. | |
| 1391 Cleanup handler is a callback with an argument which is called when pool is | |
| 1392 destroyed. | |
| 1393 Pool is usually tied with a specific nginx object (like HTTP request) and | |
| 1394 destroyed in the end of that object’s lifetime, releasing the object itself. | |
| 1902 | 1395 Registering a pool cleanup is a convenient way to release resources, close file |
| 1899 | 1396 descriptors or make final adjustments to shared data, associated with the main |
| 1397 object. | |
| 1398 </para> | |
| 1399 | |
| 1400 <para> | |
| 1401 A pool cleanup is registered by calling <literal>ngx_pool_cleanup_add(pool, | |
| 1402 size)</literal> which returns <literal>ngx_pool_cleanup_t</literal> pointer to | |
| 1403 be filled by the caller. The <literal>size</literal> argument allows allocating | |
| 1404 context for the cleanup handler. | |
| 1405 </para> | |
| 1406 | |
| 1407 | |
| 1408 <programlisting> | |
| 1409 ngx_pool_cleanup_t *cln; | |
| 1410 | |
| 1411 cln = ngx_pool_cleanup_add(pool, 0); | |
| 1412 if (cln == NULL) { /* error */ } | |
| 1413 | |
| 1414 cln->handler = ngx_my_cleanup; | |
| 1415 cln->data = “foo”; | |
| 1416 | |
| 1417 ... | |
| 1418 | |
| 1419 static void | |
| 1420 ngx_my_cleanup(void *data) | |
| 1421 { | |
| 1422 u_char *msg = data; | |
| 1423 | |
| 1424 ngx_do_smth(msg); | |
| 1425 } | |
| 1426 </programlisting> | |
| 1427 | |
| 1428 </section> | |
| 1429 | |
| 1430 | |
| 1431 <section name="Shared memory" id="shared_memory"> | |
| 1432 | |
| 1433 <para> | |
| 1434 Shared memory is used by nginx to share common data between processes. | |
| 1435 Function <literal>ngx_shared_memory_add(cf, name, size, tag)</literal> adds a | |
| 1436 new shared memory entry <literal>ngx_shm_zone_t</literal> to the cycle. The | |
| 1437 function receives <literal>name</literal> and <literal>size</literal> of the | |
| 1438 zone. | |
| 1439 Each shared zone must have a unique name. | |
| 1440 If a shared zone entry with the provided name exists, the old zone entry is | |
| 1441 reused, if its tag value matches too. | |
| 1442 Mismatched tag is considered an error. | |
| 1443 Usually, the address of the module structure is passed as tag, making it | |
| 1444 possible to reuse shared zones by name within one nginx module. | |
| 1445 </para> | |
| 1446 | |
| 1447 <para> | |
| 1448 The shared memory entry structure <literal>ngx_shm_zone_t</literal> has the | |
| 1449 following fields: | |
| 1450 </para> | |
| 1451 | |
| 1452 <para> | |
| 1453 <list type="bullet"> | |
| 1454 | |
| 1455 <listitem> | |
| 1456 <literal>init</literal> - initialization callback, called after shared zone is | |
| 1457 mapped to actual memory | |
| 1458 </listitem> | |
| 1459 | |
| 1460 <listitem> | |
| 1461 <literal>data</literal> - data context, used to pass arbitrary data to the | |
| 1462 <literal>init</literal> callback | |
| 1463 </listitem> | |
| 1464 | |
| 1465 <listitem> | |
| 1466 <literal>noreuse</literal> - flag, disabling shared zone reuse from the | |
| 1467 old cycle | |
| 1468 </listitem> | |
| 1469 | |
| 1470 <listitem> | |
| 1471 <literal>tag</literal> - shared zone tag | |
| 1472 </listitem> | |
| 1473 | |
| 1474 <listitem> | |
| 1475 <literal>shm</literal> - platform-specific object of type | |
| 1476 <literal>ngx_shm_t</literal>, having at least the following fields: | |
| 1477 <list type="bullet"> | |
| 1478 | |
| 1479 <listitem> | |
| 1480 <literal>addr</literal> - mapped shared memory address, initially NULL | |
| 1481 </listitem> | |
| 1482 | |
| 1483 <listitem> | |
| 1484 <literal>size</literal> - shared memory size | |
| 1485 </listitem> | |
| 1486 | |
| 1487 <listitem> | |
| 1488 <literal>name</literal> - shared memory name | |
| 1489 </listitem> | |
| 1490 | |
| 1491 <listitem> | |
| 1492 <literal>log</literal> - shared memory log | |
| 1493 </listitem> | |
| 1494 | |
| 1495 <listitem> | |
| 1496 <literal>exists</literal> - flag, showing that shared memory was inherited | |
| 1497 from the master process (Windows-specific) | |
| 1498 </listitem> | |
| 1499 | |
| 1500 </list> | |
| 1501 </listitem> | |
| 1502 | |
| 1503 </list> | |
| 1504 </para> | |
| 1505 | |
| 1506 <para> | |
| 1507 Shared zone entries are mapped to actual memory in | |
| 1508 <literal>ngx_init_cycle()</literal> after configuration is parsed. | |
| 1509 On POSIX systems, <literal>mmap()</literal> syscall is used to create shared | |
| 1510 anonymous mapping. | |
| 1511 On Windows, <literal>CreateFileMapping()/MapViewOfFileEx()</literal> pair is | |
| 1512 used. | |
| 1513 </para> | |
| 1514 | |
| 1515 <para> | |
| 1516 For allocating in shared memory, nginx provides slab pool | |
| 1517 <literal>ngx_slab_pool_t</literal>. | |
| 1518 In each nginx shared zone, a slab pool is automatically created for allocating | |
| 1519 memory in that zone. | |
| 1520 The pool is located in the beginning of the shared zone and can be accessed by | |
| 1521 the expression <literal>(ngx_slab_pool_t *) shm_zone->shm.addr</literal>. | |
| 1522 Allocation in shared zone is done by calling one of the functions | |
| 1523 <literal>ngx_slab_alloc(pool, size)/ngx_slab_calloc(pool, size)</literal>. | |
| 1524 Memory is freed by calling <literal>ngx_slab_free(pool, p)</literal>. | |
| 1525 </para> | |
| 1526 | |
| 1527 <para> | |
| 1528 Slab pool divides all shared zone into pages. | |
| 1529 Each page is used for allocating objects of the same size. | |
| 1530 Only the sizes which are powers of 2, and not less than 8, are considered. | |
| 1531 Other sizes are rounded up to one of these values. | |
| 1532 For each page, a bitmask is kept, showing which blocks within that page are in | |
| 1533 use and which are free for allocation. | |
| 1534 For sizes greater than half-page (usually, 2048 bytes), allocation is done by | |
| 1535 entire pages. | |
| 1536 </para> | |
| 1537 | |
| 1538 <para> | |
| 1539 To protect data in shared memory from concurrent access, mutex is available in | |
| 1540 the <literal>mutex</literal> field of <literal>ngx_slab_pool_t</literal>. | |
| 1541 The mutex is used by the slab pool while allocating and freeing memory. | |
| 1542 However, it can be used to protect any other user data structures, | |
| 1543 allocated in the shared zone. | |
| 1544 Locking is done by calling | |
| 1545 <literal>ngx_shmtx_lock(&shpool->mutex)</literal>, unlocking is done by | |
| 1546 calling <literal>ngx_shmtx_unlock(&shpool->mutex)</literal>. | |
| 1547 </para> | |
| 1548 | |
| 1549 | |
| 1550 <programlisting> | |
| 1551 ngx_str_t name; | |
| 1552 ngx_foo_ctx_t *ctx; | |
| 1553 ngx_shm_zone_t *shm_zone; | |
| 1554 | |
| 1555 ngx_str_set(&name, "foo"); | |
| 1556 | |
| 1557 /* allocate shared zone context */ | |
| 1558 ctx = ngx_pcalloc(cf->pool, sizeof(ngx_foo_ctx_t)); | |
| 1559 if (ctx == NULL) { | |
| 1560 /* error */ | |
| 1561 } | |
| 1562 | |
| 1563 /* add an entry for 65k shared zone */ | |
| 1564 shm_zone = ngx_shared_memory_add(cf, &name, 65536, &ngx_foo_module); | |
| 1565 if (shm_zone == NULL) { | |
| 1566 /* error */ | |
| 1567 } | |
| 1568 | |
| 1569 /* register init callback and context */ | |
| 1570 shm_zone->init = ngx_foo_init_zone; | |
| 1571 shm_zone->data = ctx; | |
| 1572 | |
| 1573 | |
| 1574 ... | |
| 1575 | |
| 1576 | |
| 1577 static ngx_int_t | |
| 1578 ngx_foo_init_zone(ngx_shm_zone_t *shm_zone, void *data) | |
| 1579 { | |
| 1580 ngx_foo_ctx_t *octx = data; | |
| 1581 | |
| 1582 size_t len; | |
| 1583 ngx_foo_ctx_t *ctx; | |
| 1584 ngx_slab_pool_t *shpool; | |
| 1585 | |
| 1586 value = shm_zone->data; | |
| 1587 | |
| 1588 if (octx) { | |
| 1589 /* reusing a shared zone from old cycle */ | |
| 1590 ctx->value = octx->value; | |
| 1591 return NGX_OK; | |
| 1592 } | |
| 1593 | |
| 1594 shpool = (ngx_slab_pool_t *) shm_zone->shm.addr; | |
| 1595 | |
| 1596 if (shm_zone->shm.exists) { | |
| 1597 /* initialize shared zone context in Windows nginx worker */ | |
| 1598 ctx->value = shpool->data; | |
| 1599 return NGX_OK; | |
| 1600 } | |
| 1601 | |
| 1602 /* initialize shared zone */ | |
| 1603 | |
| 1604 ctx->value = ngx_slab_alloc(shpool, sizeof(ngx_uint_t)); | |
| 1605 if (ctx->value == NULL) { | |
| 1606 return NGX_ERROR; | |
| 1607 } | |
| 1608 | |
| 1609 shpool->data = ctx->value; | |
| 1610 | |
| 1611 return NGX_OK; | |
| 1612 } | |
| 1613 </programlisting> | |
| 1614 | |
| 1615 </section> | |
| 1616 | |
| 1617 | |
| 1618 </section> | |
| 1619 | |
| 1620 | |
| 1621 <section name="Logging" id="logging"> | |
| 1622 | |
| 1623 <para> | |
| 1624 For logging nginx code uses <literal>ngx_log_t</literal> objects. | |
| 1625 Nginx logger provides support for several types of output: | |
| 1626 | |
| 1627 <list type="bullet"> | |
| 1628 | |
| 1629 <listitem> | |
| 1630 stderr - logging to standard error output | |
| 1631 </listitem> | |
| 1632 | |
| 1633 <listitem> | |
| 1634 file - logging to file | |
| 1635 </listitem> | |
| 1636 | |
| 1637 <listitem> | |
| 1638 syslog - logging to syslog | |
| 1639 </listitem> | |
| 1640 | |
| 1641 <listitem> | |
| 1642 memory - logging to internal memory storage for development purposes. | |
| 1643 The memory could be accessed later with debugger | |
| 1644 </listitem> | |
| 1645 | |
| 1646 </list> | |
| 1647 </para> | |
| 1648 | |
| 1649 <para> | |
| 1650 A logger instance may actually be a chain of loggers, linked to each other with | |
| 1651 the <literal>next</literal> field. | |
| 1652 Each message is written to all loggers in chain. | |
| 1653 </para> | |
| 1654 | |
| 1655 <para> | |
| 1656 Each logger has an error level which limits the messages written to that log. | |
| 1657 The following error levels are supported by nginx: | |
| 1658 </para> | |
| 1659 | |
| 1660 <para> | |
| 1661 <list type="bullet"> | |
| 1662 | |
| 1663 <listitem> | |
| 1664 <literal>NGX_LOG_EMERG</literal> | |
| 1665 </listitem> | |
| 1666 | |
| 1667 <listitem> | |
| 1668 <literal>NGX_LOG_ALERT</literal> | |
| 1669 </listitem> | |
| 1670 | |
| 1671 <listitem> | |
| 1672 <literal>NGX_LOG_CRIT</literal> | |
| 1673 </listitem> | |
| 1674 | |
| 1675 <listitem> | |
| 1676 <literal>NGX_LOG_ERR</literal> | |
| 1677 </listitem> | |
| 1678 | |
| 1679 <listitem> | |
| 1680 <literal>NGX_LOG_WARN</literal> | |
| 1681 </listitem> | |
| 1682 | |
| 1683 <listitem> | |
| 1684 <literal>NGX_LOG_NOTICE</literal> | |
| 1685 </listitem> | |
| 1686 | |
| 1687 <listitem> | |
| 1688 <literal>NGX_LOG_INFO</literal> | |
| 1689 </listitem> | |
| 1690 | |
| 1691 <listitem> | |
| 1692 <literal>NGX_LOG_DEBUG</literal> | |
| 1693 </listitem> | |
| 1694 | |
| 1695 </list> | |
| 1696 </para> | |
| 1697 | |
| 1698 <para> | |
| 1699 For debug logging, debug mask is checked as well. The following debug masks | |
| 1700 exist: | |
| 1701 </para> | |
| 1702 | |
| 1703 <para> | |
| 1704 <list type="bullet"> | |
| 1705 | |
| 1706 <listitem> | |
| 1707 <literal>NGX_LOG_DEBUG_CORE</literal> | |
| 1708 </listitem> | |
| 1709 | |
| 1710 <listitem> | |
| 1711 <literal>NGX_LOG_DEBUG_ALLOC</literal> | |
| 1712 </listitem> | |
| 1713 | |
| 1714 <listitem> | |
| 1715 <literal>NGX_LOG_DEBUG_MUTEX</literal> | |
| 1716 </listitem> | |
| 1717 | |
| 1718 <listitem> | |
| 1719 <literal>NGX_LOG_DEBUG_EVENT</literal> | |
| 1720 </listitem> | |
| 1721 | |
| 1722 <listitem> | |
| 1723 <literal>NGX_LOG_DEBUG_HTTP</literal> | |
| 1724 </listitem> | |
| 1725 | |
| 1726 <listitem> | |
| 1727 <literal>NGX_LOG_DEBUG_MAIL</literal> | |
| 1728 </listitem> | |
| 1729 | |
| 1730 <listitem> | |
| 1731 <literal>NGX_LOG_DEBUG_STREAM</literal> | |
| 1732 </listitem> | |
| 1733 | |
| 1734 </list> | |
| 1735 </para> | |
| 1736 | |
| 1737 <para> | |
| 1738 Normally, loggers are created by existing nginx code from | |
| 1739 <literal>error_log</literal> directives and are available at nearly every stage | |
| 1740 of processing in cycle, configuration, client connection and other objects. | |
| 1741 </para> | |
| 1742 | |
| 1743 <para> | |
| 1744 Nginx provides the following logging macros: | |
| 1745 </para> | |
| 1746 | |
| 1747 <para> | |
| 1748 <list type="bullet"> | |
| 1749 | |
| 1750 <listitem> | |
| 1751 <literal>ngx_log_error(level, log, err, fmt, ...)</literal> - error logging | |
| 1752 </listitem> | |
| 1753 | |
| 1754 <listitem> | |
| 1755 <literal>ngx_log_debug0(level, log, err, fmt)</literal>, | |
| 1756 <literal>ngx_log_debug1(level, log, err, fmt, arg1)</literal> etc - debug | |
| 1757 logging, up to 8 formatting arguments are supported | |
| 1758 </listitem> | |
| 1759 | |
| 1760 </list> | |
| 1761 </para> | |
| 1762 | |
| 1763 <para> | |
| 1764 A log message is formatted in a buffer of size | |
| 1765 <literal>NGX_MAX_ERROR_STR</literal> (currently, 2048 bytes) on stack. | |
| 1766 The message is prepended with error level, process PID, connection id (stored | |
| 1767 in <literal>log->connection</literal>) and system error text. | |
| 1768 For non-debug messages <literal>log->handler</literal> is called as well to | |
| 1769 prepend more specific information to the log message. | |
| 1770 HTTP module sets <literal>ngx_http_log_error()</literal> function as log | |
| 1771 handler to log client and server addresses, current action (stored in | |
| 1772 <literal>log->action</literal>), client request line, server name etc. | |
| 1773 </para> | |
| 1774 | |
| 1775 <para> | |
| 1776 Example: | |
| 1777 </para> | |
| 1778 | |
| 1779 | |
| 1780 <programlisting> | |
| 1781 /* specify what is currently done */ | |
| 1782 log->action = "sending mp4 to client”; | |
| 1783 | |
| 1784 /* error and debug log */ | |
| 1785 ngx_log_error(NGX_LOG_INFO, c->log, 0, "client prematurely | |
| 1786 closed connection”); | |
| 1787 | |
| 1788 ngx_log_debug2(NGX_LOG_DEBUG_HTTP, mp4->file.log, 0, | |
| 1789 "mp4 start:%ui, length:%ui”, mp4->start, mp4->length); | |
| 1790 </programlisting> | |
| 1791 | |
| 1792 <para> | |
| 1793 Logging result: | |
| 1794 </para> | |
| 1795 | |
| 1796 | |
| 1797 <programlisting> | |
| 1798 2016/09/16 22:08:52 [info] 17445#0: *1 client prematurely closed connection while | |
| 1799 sending mp4 to client, client: 127.0.0.1, server: , request: "GET /file.mp4 HTTP/1.1” | |
| 1800 2016/09/16 23:28:33 [debug] 22140#0: *1 mp4 start:0, length:10000 | |
| 1801 </programlisting> | |
| 1802 | |
| 1803 </section> | |
| 1804 | |
| 1805 | |
| 1806 <section name="Cycle" id="cycle"> | |
| 1807 | |
| 1808 <para> | |
| 1809 Cycle object keeps nginx runtime context, created from a specific | |
| 1810 configuration. | |
| 1811 The type of the cycle is <literal>ngx_cycle_t</literal>. | |
| 1812 Upon configuration reload a new cycle is created from the new version of nginx | |
| 1813 configuration. | |
| 1814 The old cycle is usually deleted after a new one is successfully created. | |
| 1815 Currently active cycle is held in the <literal>ngx_cycle</literal> global | |
| 1816 variable and is inherited by newly started nginx workers. | |
| 1817 </para> | |
| 1818 | |
| 1819 <para> | |
| 1820 A cycle is created by the function <literal>ngx_init_cycle()</literal>. | |
| 1821 The function receives the old cycle as the argument. | |
| 1822 It's used to locate the configuration file and inherit as much resources as | |
| 1823 possible from the old cycle to keep nginx running smoothly. | |
| 1824 When nginx starts, a fake cycle called "init cycle" is created and is then | |
| 1825 replaced by a normal cycle, built from configuration. | |
| 1826 </para> | |
| 1827 | |
| 1828 <para> | |
| 1829 Some members of the cycle: | |
| 1830 </para> | |
| 1831 | |
| 1832 <para> | |
| 1833 <list type="bullet"> | |
| 1834 | |
| 1835 <listitem> | |
| 1836 <literal>pool</literal> - cycle pool. Created for each new cycle | |
| 1837 </listitem> | |
| 1838 | |
| 1839 <listitem> | |
| 1840 <literal>log</literal> - cycle log. Initially, this log is inherited from the | |
| 1841 old cycle. | |
| 1842 After reading configuration, this member is set to point to | |
| 1843 <literal>new_log</literal> | |
| 1844 </listitem> | |
| 1845 | |
| 1846 <listitem> | |
| 1847 <literal>new_log</literal> - cycle log, created by the configuration. | |
| 1848 It's affected by the root scope <literal>error_log</literal> directive | |
| 1849 </listitem> | |
| 1850 | |
| 1851 <listitem> | |
| 1852 <literal>connections</literal>, <literal>connections_n</literal> - per-worker | |
| 1853 array of connections of type <literal>ngx_connection_t</literal>, created by | |
| 1854 the event module while initializing each nginx worker. | |
| 1855 The number of connections is set by the <literal>worker_connections</literal> | |
| 1856 directive | |
| 1857 </listitem> | |
| 1858 | |
| 1859 <listitem> | |
| 1860 <literal>free_connections</literal>, | |
| 1861 <literal>free_connections_n</literal> - the and number of currently available | |
| 1862 connections. | |
| 1863 If no connections are available, nginx worker refuses to accept new clients | |
| 1864 </listitem> | |
| 1865 | |
| 1866 <listitem> | |
| 1867 <literal>files</literal>, <literal>files_n</literal> - array for mapping file | |
| 1868 descriptors to nginx connections. | |
| 1869 This mapping is used by the event modules, having the | |
| 1870 <literal>NGX_USE_FD_EVENT</literal> flag (currently, it's poll and devpoll) | |
| 1871 </listitem> | |
| 1872 | |
| 1873 <listitem> | |
| 1874 <literal>conf_ctx</literal> - array of core module configurations. | |
| 1875 The configurations are created and filled while reading nginx configuration | |
| 1876 files | |
| 1877 </listitem> | |
| 1878 | |
| 1879 <listitem> | |
| 1880 <literal>modules</literal>, <literal>modules_n</literal> - array of modules | |
| 1881 <literal>ngx_module_t</literal>, both static and dynamic, loaded by current | |
| 1882 configuration | |
| 1883 </listitem> | |
| 1884 | |
| 1885 <listitem> | |
| 1886 <literal>listening</literal> - array of listening objects | |
| 1887 <literal>ngx_listening_t</literal>. | |
| 1888 Listening objects are normally added by the the <literal>listen</literal> | |
| 1889 directive of different modules which call the | |
| 1890 <literal>ngx_create_listening()</literal> function. | |
| 1891 Based on listening objects, listen sockets are created by nginx | |
| 1892 </listitem> | |
| 1893 | |
| 1894 <listitem> | |
| 1895 <literal>paths</literal> - array of paths <literal>ngx_path_t</literal>. | |
| 1896 Paths are added by calling the function <literal>ngx_add_path()</literal> from | |
| 1897 modules which are going to operate on certain directories. | |
| 1898 These directories are created by nginx after reading configuration, if missing. | |
| 1899 Moreover, two handlers can be added for each path: | |
| 1900 | |
| 1901 <list type="bullet"> | |
| 1902 | |
| 1903 <listitem> | |
| 1904 path loader - executed only once in 60 seconds after starting or reloading | |
| 1905 nginx. Normally, reads the directory and stores data in nginx shared | |
| 1906 memory. The handler is called from a dedicated nginx process "nginx | |
| 1907 cache loader" | |
| 1908 </listitem> | |
| 1909 | |
| 1910 <listitem> | |
| 1911 path manager - executed periodically. Normally, removes old files from the | |
| 1912 directory and reflects these changes in nginx memory. The handler is | |
| 1913 called from a dedicated nginx process "nginx cache manager" | |
| 1914 </listitem> | |
| 1915 | |
| 1916 </list> | |
| 1917 </listitem> | |
| 1918 | |
| 1919 <listitem> | |
| 1920 <literal>open_files</literal> - list of <literal>ngx_open_file_t</literal> | |
| 1921 objects. | |
| 1922 An open file object is created by calling the function | |
| 1923 <literal>ngx_conf_open_file()</literal>. | |
| 1924 After reading configuration nginx opens all files from the | |
| 1925 <literal>open_files</literal> list and stores file descriptors in the | |
| 1926 <literal>fd</literal> field of each open file object. | |
| 1927 The files are opened in append mode and created if missing. | |
| 1928 The files from this list are reopened by nginx workers upon receiving the | |
| 1929 reopen signal (usually it's <literal>USR1</literal>). | |
| 1930 In this case the <literal>fd</literal> fields are changed to new descriptors. | |
| 1931 The open files are currently used for logging | |
| 1932 </listitem> | |
| 1933 | |
| 1934 <listitem> | |
| 1935 <literal>shared_memory</literal> - list of shared memory zones, each added by | |
| 1936 calling the <literal>ngx_shared_memory_add()</literal> function. | |
| 1937 Shared zones are mapped to the same address range in all nginx processes and | |
| 1938 are used to share common data, for example HTTP cache in-memory tree | |
| 1939 </listitem> | |
| 1940 | |
| 1941 </list> | |
| 1942 </para> | |
| 1943 | |
| 1944 </section> | |
| 1945 | |
| 1946 <section name="Buffer" id="buffer"> | |
| 1947 | |
| 1948 <para> | |
| 1949 For input/output operations, nginx provides the buffer type | |
| 1950 <literal>ngx_buf_t</literal>. | |
| 1951 Normally, it's used to hold data to be written to a destination or read from a | |
| 1952 source. | |
| 1953 Buffer can reference data in memory and in file. | |
| 1954 Technically it's possible that a buffer references both at the same time. | |
| 1955 Memory for the buffer is allocated separately and is not related to the buffer | |
| 1956 structure <literal>ngx_buf_t</literal>. | |
| 1957 </para> | |
| 1958 | |
| 1959 <para> | |
| 1960 The structure <literal>ngx_buf_t</literal> has the following fields: | |
| 1961 </para> | |
| 1962 | |
| 1963 <para> | |
| 1964 <list type="bullet"> | |
| 1965 | |
| 1966 <listitem> | |
| 1967 <literal>start</literal>, <literal>end</literal> - the boundaries of memory | |
| 1968 block, allocated for the buffer | |
| 1969 </listitem> | |
| 1970 | |
| 1971 <listitem> | |
| 1972 <literal>pos</literal>, <literal>last</literal> - memory buffer boundaries, | |
| 1973 normally a subrange of <literal>start</literal> .. <literal>end</literal> | |
| 1974 </listitem> | |
| 1975 | |
| 1976 <listitem> | |
| 1977 <literal>file_pos</literal>, <literal>file_last</literal> - file buffer | |
| 1978 boundaries, these are offsets from the beginning of the file | |
| 1979 </listitem> | |
| 1980 | |
| 1981 <listitem> | |
| 1982 <literal>tag</literal> - unique value, used to distinguish buffers, created by | |
| 1983 different nginx module, usually, for the purpose of buffer reuse | |
| 1984 </listitem> | |
| 1985 | |
| 1986 <listitem> | |
| 1987 <literal>file</literal> - file object | |
| 1988 </listitem> | |
| 1989 | |
| 1990 <listitem> | |
| 1991 <literal>temporary</literal> - flag, meaning that the buffer references | |
| 1992 writable memory | |
| 1993 </listitem> | |
| 1994 | |
| 1995 <listitem> | |
| 1996 <literal>memory</literal> - flag, meaning that the buffer references read-only | |
| 1997 memory | |
| 1998 </listitem> | |
| 1999 | |
| 2000 <listitem> | |
| 2001 <literal>in_file</literal> - flag, meaning that current buffer references data | |
| 2002 in a file | |
| 2003 </listitem> | |
| 2004 | |
| 2005 <listitem> | |
| 2006 <literal>flush</literal> - flag, meaning that all data prior to this buffer | |
| 2007 should be flushed | |
| 2008 </listitem> | |
| 2009 | |
| 2010 <listitem> | |
| 2011 <literal>recycled</literal> - flag, meaning that the buffer can be reused and | |
| 2012 should be consumed as soon as possible | |
| 2013 </listitem> | |
| 2014 | |
| 2015 <listitem> | |
| 2016 <literal>sync</literal> - flag, meaning that the buffer carries no data or | |
| 2017 special signal like <literal>flush</literal> or <literal>last_buf</literal>. | |
| 2018 Normally, such buffers are considered an error by nginx. This flags allows | |
| 2019 skipping the error checks | |
| 2020 </listitem> | |
| 2021 | |
| 2022 <listitem> | |
| 2023 <literal>last_buf</literal> - flag, meaning that current buffer is the last in | |
| 2024 output | |
| 2025 </listitem> | |
| 2026 | |
| 2027 <listitem> | |
| 2028 <literal>last_in_chain</literal> - flag, meaning that there's no more data | |
| 2029 buffers in a (sub)request | |
| 2030 </listitem> | |
| 2031 | |
| 2032 <listitem> | |
| 2033 <literal>shadow</literal> - reference to another buffer, related to the current | |
| 2034 buffer. Usually current buffer uses data from the shadow buffer. Once current | |
| 2035 buffer is consumed, the shadow buffer should normally also be marked as | |
| 2036 consumed | |
| 2037 </listitem> | |
| 2038 | |
| 2039 <listitem> | |
| 2040 <literal>last_shadow</literal> - flag, meaning that current buffer is the last | |
| 2041 buffer, referencing a particular shadow buffer | |
| 2042 </listitem> | |
| 2043 | |
| 2044 <listitem> | |
| 2045 <literal>temp_file</literal> - flag, meaning that the buffer is in a temporary | |
| 2046 file | |
| 2047 </listitem> | |
| 2048 | |
| 2049 </list> | |
| 2050 </para> | |
| 2051 | |
| 2052 <para> | |
| 2053 For input and output buffers are linked in chains. | |
| 2054 Chain is a sequence of chain links <literal>ngx_chain_t</literal>, defined as | |
| 2055 follows: | |
| 2056 </para> | |
| 2057 | |
| 2058 | |
| 2059 <programlisting> | |
| 2060 typedef struct ngx_chain_s ngx_chain_t; | |
| 2061 | |
| 2062 struct ngx_chain_s { | |
| 2063 ngx_buf_t *buf; | |
| 2064 ngx_chain_t *next; | |
| 2065 }; | |
| 2066 </programlisting> | |
| 2067 | |
| 2068 <para> | |
| 2069 Each chain link keeps a reference to its buffer and a reference to the next | |
| 2070 chain link. | |
| 2071 </para> | |
| 2072 | |
| 2073 <para> | |
| 2074 Example of using buffers and chains: | |
| 2075 </para> | |
| 2076 | |
| 2077 | |
| 2078 <programlisting> | |
| 2079 ngx_chain_t * | |
| 2080 ngx_get_my_chain(ngx_pool_t *pool) | |
| 2081 { | |
| 2082 ngx_buf_t *b; | |
| 2083 ngx_chain_t *out, *cl, **ll; | |
| 2084 | |
| 2085 /* first buf */ | |
| 2086 cl = ngx_alloc_chain_link(pool); | |
| 2087 if (cl == NULL) { /* error */ } | |
| 2088 | |
| 2089 b = ngx_calloc_buf(pool); | |
| 2090 if (b == NULL) { /* error */ } | |
| 2091 | |
| 2092 b->start = (u_char *) "foo"; | |
| 2093 b->pos = b->start; | |
| 2094 b->end = b->start + 3; | |
| 2095 b->last = b->end; | |
| 2096 b->memory = 1; /* read-only memory */ | |
| 2097 | |
| 2098 cl->buf = b; | |
| 2099 out = cl; | |
| 2100 ll = &cl->next; | |
| 2101 | |
| 2102 /* second buf */ | |
| 2103 cl = ngx_alloc_chain_link(pool); | |
| 2104 if (cl == NULL) { /* error */ } | |
| 2105 | |
| 2106 b = ngx_create_temp_buf(pool, 3); | |
| 2107 if (b == NULL) { /* error */ } | |
| 2108 | |
| 2109 b->last = ngx_cpymem(b->last, "foo", 3); | |
| 2110 | |
| 2111 cl->buf = b; | |
| 2112 cl->next = NULL; | |
| 2113 *ll = cl; | |
| 2114 | |
| 2115 return out; | |
| 2116 } | |
| 2117 </programlisting> | |
| 2118 | |
| 2119 </section> | |
| 2120 | |
| 2121 | |
| 2122 <section name="Networking" id="networking"> | |
| 2123 | |
| 2124 | |
| 2125 <!-- | |
| 2126 <section name="Network data types" id="network_data_types"> | |
| 2127 | |
| 2128 <para> | |
| 2129 TBD: ngx_addr_t, ngx_url_t, ngx_socket_t, ngx_sockaddr_t, parse url, parse | |
| 2130 address... | |
| 2131 </para> | |
| 2132 | |
| 2133 </section> | |
| 2134 --> | |
| 2135 | |
| 2136 <section name="Connection" id="connection"> | |
| 2137 | |
| 2138 <para> | |
| 2139 Connection type <literal>ngx_connection_t</literal> is a wrapper around a | |
| 2140 socket descriptor. Some of the structure fields are: | |
| 2141 </para> | |
| 2142 | |
| 2143 <para> | |
| 2144 <list type="bullet"> | |
| 2145 | |
| 2146 <listitem> | |
| 2147 <literal>fd</literal> - socket descriptor | |
| 2148 </listitem> | |
| 2149 | |
| 2150 <listitem> | |
| 2151 <literal>data</literal> - arbitrary connection context. | |
| 2152 Normally, a pointer to a higher level object, built on top of the connection, | |
| 2153 like HTTP request or Stream session | |
| 2154 </listitem> | |
| 2155 | |
| 2156 <listitem> | |
| 2157 <literal>read</literal>, <literal>write</literal> - read and write events for | |
| 2158 the connection | |
| 2159 </listitem> | |
| 2160 | |
| 2161 <listitem> | |
| 2162 <literal>recv</literal>, <literal>send</literal>, | |
| 2163 <literal>recv_chain</literal>, <literal>send_chain</literal> - I/O operations | |
| 2164 for the connection | |
| 2165 </listitem> | |
| 2166 | |
| 2167 <listitem> | |
| 2168 <literal>pool</literal> - connection pool | |
| 2169 </listitem> | |
| 2170 | |
| 2171 <listitem> | |
| 2172 <literal>log</literal> - connection log | |
| 2173 </listitem> | |
| 2174 | |
| 2175 <listitem> | |
| 2176 <literal>sockaddr</literal>, <literal>socklen</literal>, | |
| 2177 <literal>addr_text</literal> - remote socket address in binary and text forms | |
| 2178 </listitem> | |
| 2179 | |
| 2180 <listitem> | |
| 2181 <literal>local_sockaddr</literal>, <literal>local_socklen</literal> - local | |
| 2182 socket address in binary form. | |
| 2183 Initially, these fields are empty. | |
| 2184 Function <literal>ngx_connection_local_sockaddr()</literal> should be used to | |
| 2185 get socket local address | |
| 2186 </listitem> | |
| 2187 | |
| 2188 <listitem> | |
| 2189 <literal>proxy_protocol_addr</literal>, <literal>proxy_protocol_port</literal> | |
| 2190 - PROXY protocol client address and port, if PROXY protocol is enabled for the | |
| 2191 connection | |
| 2192 </listitem> | |
| 2193 | |
| 2194 <listitem> | |
| 2195 <literal>ssl</literal> - nginx connection SSL context | |
| 2196 </listitem> | |
| 2197 | |
| 2198 <listitem> | |
| 2199 <literal>reusable</literal> - flag, meaning, that the connection is at the | |
| 2200 state, when it can be reused | |
| 2201 </listitem> | |
| 2202 | |
| 2203 <listitem> | |
| 2204 <literal>close</literal> - flag, meaning, that the connection is being reused | |
| 2205 and should be closed | |
| 2206 </listitem> | |
| 2207 | |
| 2208 </list> | |
| 2209 </para> | |
| 2210 | |
| 2211 <para> | |
| 2212 An nginx connection can transparently encapsulate SSL layer. | |
| 2213 In this case the connection <literal>ssl</literal> field holds a pointer to an | |
| 2214 <literal>ngx_ssl_connection_t</literal> structure, keeping all SSL-related data | |
| 2215 for the connection, including <literal>SSL_CTX</literal> and | |
| 2216 <literal>SSL</literal>. | |
| 2217 The handlers <literal>recv</literal>, <literal>send</literal>, | |
| 2218 <literal>recv_chain</literal>, <literal>send_chain</literal> are set as well to | |
| 2219 SSL functions. | |
| 2220 </para> | |
| 2221 | |
| 2222 <para> | |
| 2223 The number of connections per nginx worker is limited by the | |
| 2224 <literal>worker_connections</literal> value. | |
| 2225 All connection structures are pre-created when a worker starts and stored in | |
| 2226 the <literal>connections</literal> field of the cycle object. | |
| 2227 To reach out for a connection structure, <literal>ngx_get_connection(s, | |
| 2228 log)</literal> function is used. | |
| 2229 The function receives a socket descriptor <literal>s</literal> which needs to | |
| 2230 be wrapped in a connection structure. | |
| 2231 </para> | |
| 2232 | |
| 2233 <para> | |
| 2234 Since the number of connections per worker is limited, nginx provides a | |
| 2235 way to grab connections which are currently in use. | |
| 2236 To enable or disable reuse of a connection, function | |
| 2237 <literal>ngx_reusable_connection(c, reusable)</literal> is called. | |
| 2238 Calling <literal>ngx_reusable_connection(c, 1)</literal> sets the | |
| 2239 <literal>reuse</literal> flag of the connection structure and inserts the | |
| 2240 connection in the <literal>reusable_connections_queue</literal> of the cycle. | |
| 2241 Whenever <literal>ngx_get_connection()</literal> finds out there are no | |
| 2242 available connections in the <literal>free_connections</literal> list of the | |
| 2243 cycle, it calls <literal>ngx_drain_connections()</literal> to release a | |
| 2244 specific number of reusable connections. | |
| 2245 For each such connection, the <literal>close</literal> flag is set and its read | |
| 2246 handler is called which is supposed to free the connection by calling | |
| 2247 <literal>ngx_close_connection(c)</literal> and make it available for reuse. | |
| 2248 To exit the state when a connection can be reused | |
| 2249 <literal>ngx_reusable_connection(c, 0)</literal> is called. | |
| 2250 An example of reusable connections in nginx is HTTP client connections which | |
| 2251 are marked as reusable until some data is received from the client. | |
| 2252 </para> | |
| 2253 | |
| 2254 </section> | |
| 2255 | |
| 2256 | |
| 2257 </section> | |
| 2258 | |
| 2259 | |
| 2260 <section name="Events" id="events"> | |
| 2261 | |
| 2262 | |
| 2263 <section name="Event" id="event"> | |
| 2264 | |
| 2265 <para> | |
| 2266 Event object <literal>ngx_event_t</literal> in nginx provides a way to be | |
| 2267 notified of a specific event happening. | |
| 2268 </para> | |
| 2269 | |
| 2270 <para> | |
| 2271 Some of the fields of the <literal>ngx_event_t</literal> are: | |
| 2272 </para> | |
| 2273 | |
| 2274 <para> | |
| 2275 <list type="bullet"> | |
| 2276 | |
| 2277 <listitem> | |
| 2278 <literal>data</literal> - arbitrary event context, used in event handler, | |
| 2279 usually, a pointer to a connection, tied with the event | |
| 2280 </listitem> | |
| 2281 | |
| 2282 <listitem> | |
| 2283 <literal>handler</literal> - callback function to be invoked when the event | |
| 2284 happens | |
| 2285 </listitem> | |
| 2286 | |
| 2287 <listitem> | |
| 2288 <literal>write</literal> - flag, meaning that this is the write event. | |
| 2289 Used to distinguish between read and write events | |
| 2290 </listitem> | |
| 2291 | |
| 2292 <listitem> | |
| 2293 <literal>active</literal> - flag, meaning that the event is registered for | |
| 2294 receiving I/O notifications, normally from notification mechanisms like epoll, | |
| 2295 kqueue, poll | |
| 2296 </listitem> | |
| 2297 | |
| 2298 <listitem> | |
| 2299 <literal>ready</literal> - flag, meaning that the event has received an | |
| 2300 I/O notification | |
| 2301 </listitem> | |
| 2302 | |
| 2303 <listitem> | |
| 2304 <literal>delayed</literal> - flag, meaning that I/O is delayed due to rate | |
| 2305 limiting | |
| 2306 </listitem> | |
| 2307 | |
| 2308 <listitem> | |
| 2309 <literal>timer</literal> - Red-Black tree node for inserting the event into | |
| 2310 the timer tree | |
| 2311 </listitem> | |
| 2312 | |
| 2313 <listitem> | |
| 2314 <literal>timer_set</literal> - flag, meaning that the event timer is set, | |
| 2315 but not yet expired | |
| 2316 </listitem> | |
| 2317 | |
| 2318 <listitem> | |
| 2319 <literal>timedout</literal> - flag, meaning that the event timer has expired | |
| 2320 </listitem> | |
| 2321 | |
| 2322 <listitem> | |
| 2323 <literal>eof</literal> - read event flag, meaning that the eof has happened | |
| 2324 while reading data | |
| 2325 </listitem> | |
| 2326 | |
| 2327 <listitem> | |
| 2328 <literal>pending_eof</literal> - flag, meaning that the eof is pending on the | |
| 2329 socket, even though there may be some data available before it. | |
| 2330 The flag is delivered via <literal>EPOLLRDHUP</literal> epoll event or | |
| 2331 <literal>EV_EOF</literal> kqueue flag | |
| 2332 </listitem> | |
| 2333 | |
| 2334 <listitem> | |
| 2335 <literal>error</literal> - flag, meaning that an error has happened while | |
| 2336 reading (for read event) or writing (for write event) | |
| 2337 </listitem> | |
| 2338 | |
| 2339 <listitem> | |
| 2340 <literal>cancelable</literal> - timer event flag, meaning that the event | |
| 2341 handler should be called while performing nginx worker graceful shutdown, event | |
| 2342 though event timeout has not yet expired. The flag provides a way to finalize | |
| 2343 certain activities, for example, flush log files | |
| 2344 </listitem> | |
| 2345 | |
| 2346 <listitem> | |
| 2347 <literal>posted</literal> - flag, meaning that the event is posted to queue | |
| 2348 </listitem> | |
| 2349 | |
| 2350 <listitem> | |
| 2351 <literal>queue</literal> - queue node for posting the event to a queue | |
| 2352 </listitem> | |
| 2353 | |
| 2354 </list> | |
| 2355 </para> | |
| 2356 | |
| 2357 </section> | |
| 2358 | |
| 2359 | |
| 2360 <section name="I/O events" id="i_o_events"> | |
| 2361 | |
| 2362 <para> | |
| 2363 Each connection, received with the | |
| 2364 <literal>ngx_get_connection()</literal> call, has two events attached to it: | |
| 2365 <literal>c->read</literal> and <literal>c->write</literal>. | |
| 2366 These events are used to receive notifications about the socket being ready for | |
| 2367 reading or writing. | |
| 2368 All such events operate in Edge-Triggered mode, meaning that they only trigger | |
| 2369 notifications when the state of the socket changes. | |
| 2370 For example, doing a partial read on a socket will not make nginx deliver a | |
| 2371 repeated read notification until more data arrive in the socket. | |
| 2372 Even when the underlying I/O notification mechanism is essentially | |
| 2373 Level-Triggered (poll, select etc), nginx will turn the notifications into | |
| 2374 Edge-Triggered. | |
| 2375 To make nginx event notifications consistent across all notifications systems | |
| 2376 on different platforms, it's required, that the functions | |
| 2377 <literal>ngx_handle_read_event(rev, flags)</literal> and | |
|
1907
42ed974b83a5
Fixed the duplicated reference in development guide.
Vladimir Homutov <vl@nginx.com>
parents:
1902
diff
changeset
|
2378 <literal>ngx_handle_write_event(wev, lowat)</literal> are called after handling |
| 1899 | 2379 an I/O socket notification or calling any I/O functions on that socket. |
| 2380 Normally, these functions are called once in the end of each read or write | |
| 2381 event handler. | |
| 2382 </para> | |
| 2383 | |
| 2384 </section> | |
| 2385 | |
| 2386 | |
| 2387 <section name="Timer events" id="timer_events"> | |
| 2388 | |
| 2389 <para> | |
| 2390 An event can be set to notify a timeout expiration. | |
| 2391 The function <literal>ngx_add_timer(ev, timer)</literal> sets a timeout for an | |
| 2392 event, <literal>ngx_del_timer(ev)</literal> deletes a previously set timeout. | |
| 2393 Timeouts currently set for all existing events, are kept in a global timeout | |
| 2394 Red-Black tree <literal>ngx_event_timer_rbtree</literal>. | |
| 2395 The key in that tree has the type <literal>ngx_msec_t</literal> and is the time | |
| 2396 in milliseconds since the beginning of January 1, 1970 (modulus | |
| 2397 <literal>ngx_msec_t</literal> max value) at which the event should expire. | |
| 2398 The tree structure provides fast inserting and deleting operations, as well as | |
| 2399 accessing the nearest timeouts. | |
| 2400 The latter is used by nginx to find out for how long to wait for I/O events | |
| 2401 and for expiring timeout events afterwards. | |
| 2402 </para> | |
| 2403 | |
| 2404 </section> | |
| 2405 | |
| 2406 | |
| 2407 <section name="Posted events" id="posted_events"> | |
| 2408 | |
| 2409 <para> | |
| 2410 An event can be posted which means that its handler will be called at some | |
| 2411 point later within the current event loop iteration. | |
| 2412 Posting events is a good practice for simplifying code and escaping stack | |
| 2413 overflows. | |
| 2414 Posted events are held in a post queue. | |
| 2415 The macro <literal>ngx_post_event(ev, q)</literal> posts the event | |
| 2416 <literal>ev</literal> to the post queue <literal>q</literal>. | |
| 2417 Macro <literal>ngx_delete_posted_event(ev)</literal> deletes the event | |
| 2418 <literal>ev</literal> from whatever queue it's currently posted. | |
| 2419 Normally, events are posted to the <literal>ngx_posted_events</literal> queue. | |
| 2420 This queue is processed late in the event loop - after all I/O and timer | |
| 2421 events are already handled. | |
| 2422 The function <literal>ngx_event_process_posted()</literal> is called to process | |
| 2423 an event queue. | |
| 2424 This function calls event handlers until the queue is not empty. This means | |
| 2425 that a posted event handler can post more events to be processed within the | |
| 2426 current event loop iteration. | |
| 2427 </para> | |
| 2428 | |
| 2429 <para> | |
| 2430 Example: | |
| 2431 </para> | |
| 2432 | |
| 2433 | |
| 2434 <programlisting> | |
| 2435 void | |
| 2436 ngx_my_connection_read(ngx_connection_t *c) | |
| 2437 { | |
| 2438 ngx_event_t *rev; | |
| 2439 | |
| 2440 rev = c->read; | |
| 2441 | |
| 2442 ngx_add_timer(rev, 1000); | |
| 2443 | |
| 2444 rev->handler = ngx_my_read_handler; | |
| 2445 | |
| 2446 ngx_my_read(rev); | |
| 2447 } | |
| 2448 | |
| 2449 | |
| 2450 void | |
| 2451 ngx_my_read_handler(ngx_event_t *rev) | |
| 2452 { | |
| 2453 ssize_t n; | |
| 2454 ngx_connection_t *c; | |
| 2455 u_char buf[256]; | |
| 2456 | |
| 2457 if (rev->timedout) { /* timeout expired */ } | |
| 2458 | |
| 2459 c = rev->data; | |
| 2460 | |
| 2461 while (rev->ready) { | |
| 2462 n = c->recv(c, buf, sizeof(buf)); | |
| 2463 | |
| 2464 if (n == NGX_AGAIN) { | |
| 2465 break; | |
| 2466 } | |
| 2467 | |
| 2468 if (n == NGX_ERROR) { /* error */ } | |
| 2469 | |
| 2470 /* process buf */ | |
| 2471 } | |
| 2472 | |
| 2473 if (ngx_handle_read_event(rev, 0) != NGX_OK) { /* error */ } | |
| 2474 } | |
| 2475 </programlisting> | |
| 2476 | |
| 2477 </section> | |
| 2478 | |
| 2479 | |
| 2480 <section name="Event loop" id="event_loop"> | |
| 2481 | |
| 2482 <para> | |
| 2483 All nginx processes which do I/O, have an event loop. | |
| 2484 The only type of process which does not have I/O, is nginx master process which | |
| 2485 spends most of its time in <literal>sigsuspend()</literal> call waiting for | |
| 2486 signals to arrive. | |
| 2487 Event loop is implemented in <literal>ngx_process_events_and_timers()</literal> | |
| 2488 function. | |
| 2489 This function is called repeatedly until the process exits. | |
| 2490 It has the following stages: | |
| 2491 </para> | |
| 2492 | |
| 2493 <para> | |
| 2494 <list type="bullet"> | |
| 2495 | |
| 2496 <listitem> | |
| 2497 find nearest timeout by calling <literal>ngx_event_find_timer()</literal>. | |
| 2498 This function finds the leftmost timer tree node and returns the number of | |
| 2499 milliseconds until that node expires | |
| 2500 </listitem> | |
| 2501 | |
| 2502 <listitem> | |
| 2503 process I/O events by calling a handler, specific to event notification | |
| 2504 mechanism, chosen by nginx configuration. | |
| 2505 This handler waits for at least one I/O event to happen, but no longer, than | |
| 2506 the nearest timeout. | |
| 2507 For each read or write event which has happened, the <literal>ready</literal> | |
| 2508 flag is set and its handler is called. | |
| 2509 For Linux, normally, the <literal>ngx_epoll_process_events()</literal> handler | |
| 2510 is used which calls <literal>epoll_wait()</literal> to wait for I/O events | |
| 2511 </listitem> | |
| 2512 | |
| 2513 <listitem> | |
| 2514 expire timers by calling <literal>ngx_event_expire_timers()</literal>. | |
| 2515 The timer tree is iterated from the leftmost element to the right until a not | |
| 2516 yet expired timeout is found. | |
| 2517 For each expired node the <literal>timedout</literal> event flag is set, | |
| 2518 <literal>timer_set</literal> flag is reset, and the event handler is called | |
| 2519 </listitem> | |
| 2520 | |
| 2521 <listitem> | |
| 2522 process posted events by calling <literal>ngx_event_process_posted()</literal>. | |
| 2523 The function repeatedly removes the first element from the posted events | |
| 2524 queue and calls its handler until the queue gets empty | |
| 2525 </listitem> | |
| 2526 | |
| 2527 </list> | |
| 2528 </para> | |
| 2529 | |
| 2530 <para> | |
| 2531 All nginx processes handle signals as well. | |
| 2532 Signal handlers only set global variables which are checked after the | |
| 2533 <literal>ngx_process_events_and_timers()</literal> call. | |
| 2534 </para> | |
| 2535 | |
| 2536 </section> | |
| 2537 | |
| 2538 | |
| 2539 </section> | |
| 2540 | |
| 2541 | |
| 2542 <section name="Processes" id="processes"> | |
| 2543 | |
| 2544 <para> | |
| 2545 There are several types of processes in nginx. | |
| 2546 The type of current process is kept in the <literal>ngx_process</literal> | |
| 2547 global variable: | |
| 2548 </para> | |
| 2549 | |
| 2550 <list type="bullet"> | |
| 2551 | |
| 2552 <listitem> | |
| 2553 | |
| 2554 <para> | |
| 2555 <literal>NGX_PROCESS_MASTER</literal> - the master process runs the | |
| 2556 <literal>ngx_master_process_cycle()</literal> function. | |
| 2557 Master process does not have any I/O and responds only to signals. | |
| 2558 It reads configuration, creates cycles, starts and controls child processes | |
| 2559 </para> | |
| 2560 | |
| 2561 | |
| 2562 </listitem> | |
| 2563 | |
| 2564 <listitem> | |
| 2565 | |
| 2566 <para> | |
| 2567 <literal>NGX_PROCESS_WORKER</literal> - the worker process runs the | |
| 2568 <literal>ngx_worker_process_cycle()</literal> function. | |
| 2569 Worker processes are started by master and handle client connections. | |
| 2570 They also respond to signals and channel commands, sent from master | |
| 2571 </para> | |
| 2572 | |
| 2573 | |
| 2574 </listitem> | |
| 2575 | |
| 2576 <listitem> | |
| 2577 | |
| 2578 <para> | |
| 2579 <literal>NGX_PROCESS_SINGLE</literal> - single process is the only type | |
| 2580 of processes which exist in the <literal>master_process off</literal> mode. | |
| 2581 The cycle function for this process is | |
| 2582 <literal>ngx_single_process_cycle()</literal>. | |
| 2583 This process creates cycles and handles client connections | |
| 2584 </para> | |
| 2585 | |
| 2586 | |
| 2587 </listitem> | |
| 2588 | |
| 2589 <listitem> | |
| 2590 | |
| 2591 <para> | |
| 2592 <literal>NGX_PROCESS_HELPER</literal> - currently, there are two types of | |
| 2593 helper processes: cache manager and cache loader. | |
| 2594 Both of them share the same cycle function | |
| 2595 <literal>ngx_cache_manager_process_cycle()</literal>. | |
| 2596 </para> | |
| 2597 | |
| 2598 | |
| 2599 </listitem> | |
| 2600 | |
| 2601 </list> | |
| 2602 | |
| 2603 <para> | |
| 2604 All nginx processes handle the following signals: | |
| 2605 </para> | |
| 2606 | |
| 2607 <list type="bullet"> | |
| 2608 | |
| 2609 <listitem> | |
| 2610 | |
| 2611 <para> | |
| 2612 <literal>NGX_SHUTDOWN_SIGNAL</literal> (<literal>SIGQUIT</literal>) - graceful | |
| 2613 shutdown. | |
| 2614 Upon receiving this signal master process sends shutdown signal to all child | |
| 2615 processes. | |
| 2616 When no child processes are left, master destroys cycle pool and exits. | |
| 2617 A worker process which received this signal, closes all listening sockets and | |
| 2618 waits until timeout tree becomes empty, then destroys cycle pool and exits. | |
| 2619 A cache manager process exits right after receiving this signal. | |
| 2620 The variable <literal>ngx_quit</literal> is set to one after receiving this | |
| 2621 signal and immediately reset after being processed. | |
| 2622 The variable <literal>ngx_exiting</literal> is set to one when worker process | |
| 2623 is in shutdown state | |
| 2624 </para> | |
| 2625 | |
| 2626 | |
| 2627 </listitem> | |
| 2628 | |
| 2629 <listitem> | |
| 2630 | |
| 2631 <para> | |
| 2632 <literal>NGX_TERMINATE_SIGNAL</literal> (<literal>SIGTERM</literal>) - | |
| 2633 terminate. | |
| 2634 Upon receiving this signal master process sends terminate signal to all child | |
| 2635 processes. | |
| 2636 If child processes do not exit in 1 second, they are killed with the | |
| 2637 <literal>SIGKILL</literal> signal. | |
| 2638 When no child processes are left, master process destroys cycle pool and exits. | |
| 2639 A worker or cache manager process which received this signal destroys cycle | |
| 2640 pool and exits. | |
| 2641 The variable <literal>ngx_terminate</literal> is set to one after receiving | |
| 2642 this signal | |
| 2643 </para> | |
| 2644 | |
| 2645 | |
| 2646 </listitem> | |
| 2647 | |
| 2648 <listitem> | |
| 2649 | |
| 2650 <para> | |
| 2651 <literal>NGX_NOACCEPT_SIGNAL</literal> (<literal>SIGWINCH</literal>) | |
| 2652 - gracefully shut down worker processes | |
| 2653 </para> | |
| 2654 | |
| 2655 | |
| 2656 </listitem> | |
| 2657 | |
| 2658 <listitem> | |
| 2659 | |
| 2660 <para> | |
| 2661 <literal>NGX_RECONFIGURE_SIGNAL</literal> (<literal>SIGHUP</literal>) - | |
| 2662 reconfigure. | |
| 2663 Upon receiving this signal master process creates a new cycle from | |
| 2664 configuration file. | |
| 2665 If the new cycle was created successfully, the old cycle is deleted and new | |
| 2666 child processes are started. | |
| 2667 Meanwhile, the old processes receive the shutdown signal. | |
| 2668 In single-process mode, nginx creates a new cycle as well, but keeps the old | |
| 2669 one until all clients, tied to the old cycle, are gone. | |
| 2670 Worker and helper processes ignore this signal | |
| 2671 </para> | |
| 2672 | |
| 2673 | |
| 2674 </listitem> | |
| 2675 | |
| 2676 <listitem> | |
| 2677 | |
| 2678 <para> | |
| 2679 <literal>NGX_REOPEN_SIGNAL</literal> (<literal>SIGUSR1</literal>) - reopen | |
| 2680 files. | |
| 2681 Master process passes this signal to workers. | |
| 2682 Worker processes reopen all <literal>open_files</literal> from the cycle | |
| 2683 </para> | |
| 2684 | |
| 2685 | |
| 2686 </listitem> | |
| 2687 | |
| 2688 <listitem> | |
| 2689 | |
| 2690 <para> | |
| 2691 <literal>NGX_CHANGEBIN_SIGNAL</literal> (<literal>SIGUSR2</literal>) - change | |
| 2692 nginx binary. | |
| 2693 Master process starts a new nginx binary and passes there a list of all listen | |
| 2694 sockets. | |
| 2695 The list is passed in the environment variable <literal>"NGINX"</literal> in | |
| 2696 text format, where descriptor numbers separated with semicolons. | |
| 2697 A new nginx instance reads that variable and adds the sockets to its init | |
| 2698 cycle. | |
| 2699 Other processes ignore this signal | |
| 2700 </para> | |
| 2701 | |
| 2702 | |
| 2703 </listitem> | |
| 2704 | |
| 2705 </list> | |
| 2706 | |
| 2707 <para> | |
| 2708 While all nginx worker processes are able to receive and properly handle POSIX | |
| 2709 signals, master process normally does not pass any signals to workers and | |
| 2710 helpers with the standard <literal>kill()</literal> syscall. | |
| 2711 Instead, nginx uses inter-process channels which allow sending messages between | |
| 2712 all nginx processes. | |
| 2713 Currently, however, messages are only sent from master to its children. | |
| 2714 Those messages carry the same signals. | |
| 2715 The channels are socketpairs with their ends in different processes. | |
| 2716 </para> | |
| 2717 | |
| 2718 <para> | |
| 2719 When running nginx binary, several values can be specified next to | |
| 2720 <literal>-s</literal> parameter. | |
| 2721 Those values are <literal>stop</literal>, <literal>quit</literal>, | |
| 2722 <literal>reopen</literal>, <literal>reload</literal>. | |
| 2723 They are converted to signals <literal>NGX_TERMINATE_SIGNAL</literal>, | |
| 2724 <literal>NGX_SHUTDOWN_SIGNAL</literal>, <literal>NGX_REOPEN_SIGNAL</literal> | |
| 2725 and <literal>NGX_RECONFIGURE_SIGNAL</literal> and sent to the nginx master | |
| 2726 process, whose pid is read from nginx pid file. | |
| 2727 </para> | |
| 2728 | |
| 2729 </section> | |
| 2730 | |
| 2731 </article> |