Mercurial > hg > nginx-site
annotate xml/en/docs/dev/development_guide.xml @ 1914:f8659301a260
Added hash API description.
| author | Vladimir Homutov <vl@nginx.com> |
|---|---|
| date | Wed, 22 Feb 2017 17:27:40 +0300 |
| parents | 42ed974b83a5 |
| children | 8b7c3b0ef1a4 |
| 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
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
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. | |
| 297 They are declared in <literal>src/core/ngx_string.h</literal>. | |
| 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 | |
| 441 in <literal>src/core/ngx_string.c</literal>. Some of them are: | |
| 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 | |
| 530 | |
| 531 </section> | |
| 532 | |
| 533 | |
| 534 <section name="Containers" id="containers"> | |
| 535 | |
| 536 | |
| 537 <section name="Array" id="array"> | |
| 538 | |
| 539 <para> | |
| 540 The nginx array type <literal>ngx_array_t</literal> is defined as follows | |
| 541 </para> | |
| 542 | |
| 543 | |
| 544 <programlisting> | |
| 545 typedef struct { | |
| 546 void *elts; | |
| 547 ngx_uint_t nelts; | |
| 548 size_t size; | |
| 549 ngx_uint_t nalloc; | |
| 550 ngx_pool_t *pool; | |
| 551 } ngx_array_t; | |
| 552 </programlisting> | |
| 553 | |
| 554 <para> | |
| 555 The elements of array are available through the <literal>elts</literal> field. | |
| 556 The number of elements is held in the <literal>nelts</literal> field. | |
| 557 The <literal>size</literal> field holds the size of a single element and is set | |
| 558 when initializing the array. | |
| 559 </para> | |
| 560 | |
| 561 <para> | |
| 562 An array can be created in a pool with the | |
| 563 <literal>ngx_array_create(pool, n, size)</literal> call. | |
| 564 An already allocated array object can be initialized with the | |
| 565 <literal>ngx_array_init(array, pool, n, size)</literal> call. | |
| 566 </para> | |
| 567 | |
| 568 | |
| 569 <programlisting> | |
| 570 ngx_array_t *a, b; | |
| 571 | |
| 572 /* create an array of strings with preallocated memory for 10 elements */ | |
| 573 a = ngx_array_create(pool, 10, sizeof(ngx_str_t)); | |
| 574 | |
| 575 /* initialize string array for 10 elements */ | |
| 576 ngx_array_init(&b, pool, 10, sizeof(ngx_str_t)); | |
| 577 </programlisting> | |
| 578 | |
| 579 <para> | |
| 580 Adding elements to array are done with the following functions: | |
| 581 </para> | |
| 582 | |
| 583 <para> | |
| 584 <list type="bullet"> | |
| 585 | |
| 586 <listitem> | |
| 587 <literal>ngx_array_push(a)</literal> adds one tail element and returns pointer | |
| 588 to it | |
| 589 </listitem> | |
| 590 | |
| 591 <listitem> | |
| 592 <literal>ngx_array_push_n(a, n)</literal> adds <literal>n</literal> tail elements | |
| 593 and returns pointer to the first one | |
| 594 </listitem> | |
| 595 | |
| 596 </list> | |
| 597 </para> | |
| 598 | |
| 599 <para> | |
| 600 If currently allocated memory is not enough for new elements, a new memory for | |
| 601 elements is allocated and existing elements are copied to that memory. | |
| 602 The new memory block is normally twice as large, as the existing one. | |
| 603 </para> | |
| 604 | |
| 605 | |
| 606 <programlisting> | |
| 607 s = ngx_array_push(a); | |
| 608 ss = ngx_array_push_n(&b, 3); | |
| 609 </programlisting> | |
| 610 | |
| 611 </section> | |
| 612 | |
| 613 | |
| 614 <section name="List" id="list"> | |
| 615 | |
| 616 <para> | |
| 617 List in nginx is a sequence of arrays, optimized for inserting a potentially | |
| 618 large number of items. The list type is defined as follows: | |
| 619 </para> | |
| 620 | |
| 621 | |
| 622 <programlisting> | |
| 623 typedef struct { | |
| 624 ngx_list_part_t *last; | |
| 625 ngx_list_part_t part; | |
| 626 size_t size; | |
| 627 ngx_uint_t nalloc; | |
| 628 ngx_pool_t *pool; | |
| 629 } ngx_list_t; | |
| 630 </programlisting> | |
| 631 | |
| 632 <para> | |
| 633 The actual items are store in list parts, defined as follows: | |
| 634 </para> | |
| 635 | |
| 636 | |
| 637 <programlisting> | |
| 638 typedef struct ngx_list_part_s ngx_list_part_t; | |
| 639 | |
| 640 struct ngx_list_part_s { | |
| 641 void *elts; | |
| 642 ngx_uint_t nelts; | |
| 643 ngx_list_part_t *next; | |
| 644 }; | |
| 645 </programlisting> | |
| 646 | |
| 647 <para> | |
| 648 Initially, a list must be initialized by calling | |
| 649 <literal>ngx_list_init(list, pool, n, size)</literal> or created by calling | |
| 650 <literal>ngx_list_create(pool, n, size)</literal>. | |
| 651 Both functions receive the size of a single item and a number of items per list | |
| 652 part. | |
| 653 The <literal>ngx_list_push(list)</literal> function is used to add an item to the | |
| 654 list. Iterating over the items is done by direct accessing the list fields, as | |
| 655 seen in the example: | |
| 656 </para> | |
| 657 | |
| 658 | |
| 659 <programlisting> | |
| 660 ngx_str_t *v; | |
| 661 ngx_uint_t i; | |
| 662 ngx_list_t *list; | |
| 663 ngx_list_part_t *part; | |
| 664 | |
| 665 list = ngx_list_create(pool, 100, sizeof(ngx_str_t)); | |
| 666 if (list == NULL) { /* error */ } | |
| 667 | |
| 668 /* add items to the list */ | |
| 669 | |
| 670 v = ngx_list_push(list); | |
| 671 if (v == NULL) { /* error */ } | |
| 672 ngx_str_set(v, “foo”); | |
| 673 | |
| 674 v = ngx_list_push(list); | |
| 675 if (v == NULL) { /* error */ } | |
| 676 ngx_str_set(v, “bar”); | |
| 677 | |
| 678 /* iterate over the list */ | |
| 679 | |
| 680 part = &list->part; | |
| 681 v = part->elts; | |
| 682 | |
| 683 for (i = 0; /* void */; i++) { | |
| 684 | |
| 685 if (i >= part->nelts) { | |
| 686 if (part->next == NULL) { | |
| 687 break; | |
| 688 } | |
| 689 | |
| 690 part = part->next; | |
| 691 v = part->elts; | |
| 692 i = 0; | |
| 693 } | |
| 694 | |
| 695 ngx_do_smth(&v[i]); | |
| 696 } | |
| 697 </programlisting> | |
| 698 | |
| 699 <para> | |
| 700 The primary use for the list in nginx is HTTP input and output headers. | |
| 701 </para> | |
| 702 | |
| 703 <para> | |
| 704 The list does not support item removal. | |
| 705 However, when needed, items can internally be marked as missing without actual | |
| 706 removing from the list. | |
| 707 For example, HTTP output headers which are stored as | |
| 708 <literal>ngx_table_elt_t</literal> objects, are marked as missing by setting | |
| 709 the <literal>hash</literal> field of <literal>ngx_table_elt_t</literal> to | |
| 710 zero. Such items are explicitly skipped, when iterating over the headers. | |
| 711 </para> | |
| 712 | |
| 713 </section> | |
| 714 | |
| 715 | |
| 716 <section name="Queue" id="queue"> | |
| 717 | |
| 718 <para> | |
| 719 Queue in nginx is an intrusive doubly linked list, with each node defined as | |
| 720 follows: | |
| 721 </para> | |
| 722 | |
| 723 | |
| 724 <programlisting> | |
| 725 typedef struct ngx_queue_s ngx_queue_t; | |
| 726 | |
| 727 struct ngx_queue_s { | |
| 728 ngx_queue_t *prev; | |
| 729 ngx_queue_t *next; | |
| 730 }; | |
| 731 </programlisting> | |
| 732 | |
| 733 <para> | |
| 734 The head queue node is not linked with any data. Before using, the list head | |
| 735 should be initialized with <literal>ngx_queue_init(q)</literal> call. | |
| 736 Queues support the following operations: | |
| 737 </para> | |
| 738 | |
| 739 <para> | |
| 740 <list type="bullet"> | |
| 741 | |
| 742 <listitem> | |
| 743 <literal>ngx_queue_insert_head(h, x)</literal>, | |
| 744 <literal>ngx_queue_insert_tail(h, x)</literal> - insert a new node | |
| 745 </listitem> | |
| 746 | |
| 747 <listitem> | |
| 748 <literal>ngx_queue_remove(x)</literal> - remove a queue node | |
| 749 </listitem> | |
| 750 | |
| 751 <listitem> | |
| 752 <literal>ngx_queue_split(h, q, n)</literal> - split a queue at a node, | |
| 753 queue tail is returned in a separate queue | |
| 754 </listitem> | |
| 755 | |
| 756 <listitem> | |
| 757 <literal>ngx_queue_add(h, n)</literal> - add second queue to the first queue | |
| 758 </listitem> | |
| 759 | |
| 760 <listitem> | |
| 761 <literal>ngx_queue_head(h)</literal>, | |
| 762 <literal>ngx_queue_last(h)</literal> - get first or last queue node | |
| 763 </listitem> | |
| 764 | |
| 765 <listitem> | |
| 766 <literal>ngx_queue_sentinel(h)</literal> | |
| 767 - get a queue sentinel object to end iteration at | |
| 768 </listitem> | |
| 769 | |
| 770 <listitem> | |
| 771 <literal>ngx_queue_data(q, type, link)</literal> - get reference to the beginning of a | |
| 772 queue node data structure, considering the queue field offset in it | |
| 773 </listitem> | |
| 774 | |
| 775 </list> | |
| 776 </para> | |
| 777 | |
| 778 <para> | |
| 779 Example: | |
| 780 </para> | |
| 781 | |
| 782 | |
| 783 <programlisting> | |
| 784 typedef struct { | |
| 785 ngx_str_t value; | |
| 786 ngx_queue_t queue; | |
| 787 } ngx_foo_t; | |
| 788 | |
| 789 ngx_foo_t *f; | |
| 790 ngx_queue_t values; | |
| 791 | |
| 792 ngx_queue_init(&values); | |
| 793 | |
| 794 f = ngx_palloc(pool, sizeof(ngx_foo_t)); | |
| 795 if (f == NULL) { /* error */ } | |
| 796 ngx_str_set(&f->value, “foo”); | |
| 797 | |
| 798 ngx_queue_insert_tail(&values, f); | |
| 799 | |
| 800 /* insert more nodes here */ | |
| 801 | |
| 802 for (q = ngx_queue_head(&values); | |
| 803 q != ngx_queue_sentinel(&values); | |
| 804 q = ngx_queue_next(q)) | |
| 805 { | |
| 806 f = ngx_queue_data(q, ngx_foo_t, queue); | |
| 807 | |
| 808 ngx_do_smth(&f->value); | |
| 809 } | |
| 810 </programlisting> | |
| 811 | |
| 812 </section> | |
| 813 | |
| 814 | |
| 815 <section name="Red-Black tree" id="red_black_tree"> | |
| 816 | |
| 817 <para> | |
| 818 The <literal>src/core/ngx_rbtree.h</literal> header file provides access to the | |
| 819 effective implementation of red-black trees. | |
| 820 </para> | |
| 821 | |
| 822 | |
| 823 <programlisting> | |
| 824 typedef struct { | |
| 825 ngx_rbtree_t rbtree; | |
| 826 ngx_rbtree_node_t sentinel; | |
| 827 | |
| 828 /* custom per-tree data here */ | |
| 829 } my_tree_t; | |
| 830 | |
| 831 typedef struct { | |
| 832 ngx_rbtree_node_t rbnode; | |
| 833 | |
| 834 /* custom per-node data */ | |
| 835 foo_t val; | |
| 836 } my_node_t; | |
| 837 </programlisting> | |
| 838 | |
| 839 <para> | |
| 840 To deal with a tree as a whole, you need two nodes: root and sentinel. | |
| 841 Typically, they are added to some custom structure, thus allowing to | |
| 842 organize your data into a tree which leaves contain a link to or embed | |
| 843 your data. | |
| 844 </para> | |
| 845 | |
| 846 <para> | |
| 847 To initialize a tree: | |
| 848 </para> | |
| 849 | |
| 850 | |
| 851 <programlisting> | |
| 852 my_tree_t root; | |
| 853 | |
| 854 ngx_rbtree_init(&root.rbtree, &root.sentinel, insert_value_function); | |
| 855 </programlisting> | |
| 856 | |
| 857 <para> | |
| 858 The <literal>insert_value_function</literal> is a function that is | |
| 859 responsible for traversing the tree and inserting new values into correct | |
| 860 place. | |
| 861 For example, the <literal>ngx_str_rbtree_insert_value</literal> functions is | |
| 862 designed to deal with <literal>ngx_str_t</literal> type. | |
| 863 </para> | |
| 864 | |
| 865 | |
| 866 <programlisting> | |
| 867 void ngx_str_rbtree_insert_value(ngx_rbtree_node_t *temp, | |
| 868 ngx_rbtree_node_t *node, | |
| 869 ngx_rbtree_node_t *sentinel) | |
| 870 </programlisting> | |
| 871 | |
| 872 <para> | |
| 873 Its arguments are pointers to a root node of an insertion, newly created node | |
| 874 to be added, and a tree sentinel. | |
| 875 </para> | |
| 876 | |
| 877 <para> | |
| 878 The traversal is pretty straightforward and can be demonstrated with the | |
| 879 following lookup function pattern: | |
| 880 </para> | |
| 881 | |
| 882 | |
| 883 <programlisting> | |
| 884 my_node_t * | |
| 885 my_rbtree_lookup(ngx_rbtree_t *rbtree, foo_t *val, uint32_t hash) | |
| 886 { | |
| 887 ngx_int_t rc; | |
| 888 my_node_t *n; | |
| 889 ngx_rbtree_node_t *node, *sentinel; | |
| 890 | |
| 891 node = rbtree->root; | |
| 892 sentinel = rbtree->sentinel; | |
| 893 | |
| 894 while (node != sentinel) { | |
| 895 | |
| 896 n = (my_node_t *) node; | |
| 897 | |
| 898 if (hash != node->key) { | |
| 899 node = (hash < node->key) ? node->left : node->right; | |
| 900 continue; | |
| 901 } | |
| 902 | |
| 903 rc = compare(val, node->val); | |
| 904 | |
| 905 if (rc < 0) { | |
| 906 node = node->left; | |
| 907 continue; | |
| 908 } | |
| 909 | |
| 910 if (rc > 0) { | |
| 911 node = node->right; | |
| 912 continue; | |
| 913 } | |
| 914 | |
| 915 return n; | |
| 916 } | |
| 917 | |
| 918 return NULL; | |
| 919 } | |
| 920 </programlisting> | |
| 921 | |
| 922 <para> | |
| 923 The <literal>compare()</literal> is a classic comparator function returning | |
| 924 value less, equal or greater than zero. To speed up lookups and avoid comparing | |
| 925 user objects that can be big, integer hash field is used. | |
| 926 </para> | |
| 927 | |
| 928 <para> | |
| 929 To add a node to a tree, allocate a new node, initialize it and call | |
| 930 <literal>ngx_rbtree_insert()</literal>: | |
| 931 </para> | |
| 932 | |
| 933 | |
| 934 <programlisting> | |
| 935 my_node_t *my_node; | |
| 936 ngx_rbtree_node_t *node; | |
| 937 | |
| 938 my_node = ngx_palloc(...); | |
| 939 init_custom_data(&my_node->val); | |
| 940 | |
| 941 node = &my_node->rbnode; | |
| 942 node->key = create_key(my_node->val); | |
| 943 | |
| 944 ngx_rbtree_insert(&root->rbtree, node); | |
| 945 </programlisting> | |
| 946 | |
| 947 <para> | |
| 948 to remove a node: | |
| 949 </para> | |
| 950 | |
| 951 | |
| 952 <programlisting> | |
| 953 ngx_rbtree_delete(&root->rbtree, node); | |
| 954 </programlisting> | |
| 955 | |
| 956 </section> | |
| 957 | |
|
1914
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
958 <section name="Hash" id="hash"> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
959 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
960 <para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
961 Hash table functions are are declared in <path>src/core/ngx_string.h</path>. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
962 Exact and wildcard matching is supported. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
963 The latter requires extra setup and is described in a separate section below. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
964 </para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
965 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
966 <para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
967 To initialize a hash, one needs to know the number of elements in advance, |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
968 so that nginx can build the hash optimally. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
969 Two parameters that need to be configured are <literal>max_size</literal> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
970 and <literal>bucket_size</literal>. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
971 The details of setting up these are provided in a separate |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
972 <link doc="../hash.xml">document</link>. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
973 Usually, these two parameters are configurable by user. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
974 Hash initialization settings are stored as the |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
975 <literal>ngx_hash_init_t</literal> type, |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
976 and the hash itself is <literal>ngx_hash_t</literal>: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
977 <programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
978 ngx_hash_t foo_hash; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
979 ngx_hash_init_t hash; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
980 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
981 hash.hash = &foo_hash; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
982 hash.key = ngx_hash_key; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
983 hash.max_size = 512; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
984 hash.bucket_size = ngx_align(64, ngx_cacheline_size); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
985 hash.name = "foo_hash"; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
986 hash.pool = cf->pool; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
987 hash.temp_pool = cf->temp_pool; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
988 </programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
989 The <literal>key</literal> is a pointer to a function that creates hash integer |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
990 key from a string. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
991 Two generic functions are provided: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
992 <literal>ngx_hash_key(data, len)</literal> and |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
993 <literal>ngx_hash_key_lc(data, len)</literal>. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
994 The latter converts a string to lowercase and thus requires the passed string to |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
995 be writable. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
996 If this is not true, <literal>NGX_HASH_READONLY_KEY</literal> flag |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
997 may be passed to the function, initializing array keys (see below). |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
998 </para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
999 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1000 <para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1001 The hash keys are stored in <literal>ngx_hash_keys_arrays_t</literal> and |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1002 are initialized with <literal>ngx_hash_keys_array_init(arr, type)</literal>: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1003 <programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1004 ngx_hash_keys_arrays_t foo_keys; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1005 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1006 foo_keys.pool = cf->pool; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1007 foo_keys.temp_pool = cf->temp_pool; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1008 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1009 ngx_hash_keys_array_init(&foo_keys, NGX_HASH_SMALL); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1010 </programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1011 The second parameter can be either <literal>NGX_HASH_SMALL</literal> or |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1012 <literal>NGX_HASH_LARGE</literal> and controls the amount of preallocated |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1013 resources for the hash. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1014 If you expect the hash to contain thousands elements, |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1015 use <literal>NGX_HASH_LARGE</literal>. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1016 </para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1017 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1018 <para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1019 The <literal>ngx_hash_add_key(keys_array, key, value, flags)</literal> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1020 function is used to insert keys into hash keys array; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1021 <programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1022 ngx_str_t k1 = ngx_string("key1"); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1023 ngx_str_t k2 = ngx_string("key2"); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1024 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1025 ngx_hash_add_key(&foo_keys, &k1, &my_data_ptr_1, NGX_HASH_READONLY_KEY); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1026 ngx_hash_add_key(&foo_keys, &k2, &my_data_ptr_2, NGX_HASH_READONLY_KEY); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1027 </programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1028 </para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1029 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1030 <para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1031 Now, the hash table may be built using the call to |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1032 <literal>ngx_hash_init(hinit, key_names, nelts)</literal>: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1033 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1034 <programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1035 ngx_hash_init(&hash, foo_keys.keys.elts, foo_keys.keys.nelts); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1036 </programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1037 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1038 This may fail, if <literal>max_size</literal> or <literal>bucket_size</literal> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1039 parameters are not big enough. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1040 When the hash is built, <literal>ngx_hash_find(hash, key, name, len)</literal> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1041 function may be used to look up elements: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1042 <programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1043 my_data_t *data; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1044 ngx_uint_t key; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1045 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1046 key = ngx_hash_key(k1.data, k1.len); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1047 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1048 data = ngx_hash_find(&foo_hash, key, k1.data, k1.len); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1049 if (data == NULL) { |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1050 /* key not found */ |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1051 } |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1052 </programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1053 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1054 </para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1055 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1056 <section name="Wildcard matching" id="wildcard_matching"> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1057 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1058 <para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1059 To create a hash that works with wildcards, |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1060 <literal>ngx_hash_combined_t</literal> type is used. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1061 It includes the hash type described above and has two additional keys arrays: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1062 <literal>dns_wc_head</literal> and <literal>dns_wc_tail</literal>. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1063 The initialization of basic properties is done similarly to a usual hash: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1064 <programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1065 ngx_hash_init_t hash |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1066 ngx_hash_combined_t foo_hash; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1067 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1068 hash.hash = &foo_hash.hash; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1069 hash.key = ...; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1070 </programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1071 </para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1072 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1073 <para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1074 It is possible to add wildcard keys using the |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1075 <literal>NGX_HASH_WILDCARD_KEY</literal> flag: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1076 <programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1077 /* k1 = ".example.org"; */ |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1078 /* k2 = "foo.*"; */ |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1079 ngx_hash_add_key(&foo_keys, &k1, &data1, NGX_HASH_WILDCARD_KEY); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1080 ngx_hash_add_key(&foo_keys, &k2, &data2, NGX_HASH_WILDCARD_KEY); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1081 </programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1082 The function recognizes wildcards and adds keys into corresponding arrays. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1083 Please refer to the |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1084 <link doc="../http/ngx_http_map_module.xml" id="map"/> module |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1085 documentation for the description of the wildcard syntax and |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1086 matching algorithm. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1087 </para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1088 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1089 <para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1090 Depending on the contents of added keys, you may need to initialize up to three |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1091 keys arrays: one for exact matching (described above), and two for matching |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1092 starting from head or tail of a string: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1093 <programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1094 if (foo_keys.dns_wc_head.nelts) { |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1095 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1096 ngx_qsort(foo_keys.dns_wc_head.elts, |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1097 (size_t) foo_keys.dns_wc_head.nelts, |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1098 sizeof(ngx_hash_key_t), |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1099 cmp_dns_wildcards); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1100 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1101 hash.hash = NULL; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1102 hash.temp_pool = pool; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1103 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1104 if (ngx_hash_wildcard_init(&hash, foo_keys.dns_wc_head.elts, |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1105 foo_keys.dns_wc_head.nelts) |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1106 != NGX_OK) |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1107 { |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1108 return NGX_ERROR; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1109 } |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1110 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1111 foo_hash.wc_head = (ngx_hash_wildcard_t *) hash.hash; |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1112 } |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1113 </programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1114 The keys array needs to be sorted, and initialization results must be added |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1115 to the combined hash. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1116 The initialization of <literal>dns_wc_tail</literal> array is done similarly. |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1117 </para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1118 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1119 <para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1120 The lookup in a combined hash is handled by the |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1121 <literal>ngx_hash_find_combined(chash, key, name, len)</literal>: |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1122 <programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1123 /* key = "bar.example.org"; - will match ".example.org" */ |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1124 /* key = "foo.example.com"; - will match "foo.*" */ |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1125 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1126 hkey = ngx_hash_key(key.data, key.len); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1127 res = ngx_hash_find_combined(&foo_hash, hkey, key.data, key.len); |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1128 </programlisting> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1129 </para> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1130 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1131 </section> |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1132 |
|
f8659301a260
Added hash API description.
Vladimir Homutov <vl@nginx.com>
parents:
1907
diff
changeset
|
1133 </section> |
| 1899 | 1134 |
| 1135 </section> | |
| 1136 | |
| 1137 | |
| 1138 <section name="Memory management" id="memory_management"> | |
| 1139 | |
| 1140 | |
| 1141 <section name="Heap" id="heap"> | |
| 1142 | |
| 1143 <para> | |
| 1144 To allocate memory from system heap, the following functions are provided by | |
| 1145 nginx: | |
| 1146 </para> | |
| 1147 | |
| 1148 <para> | |
| 1149 <list type="bullet"> | |
| 1150 | |
| 1151 <listitem> | |
| 1152 <literal>ngx_alloc(size, log)</literal> - allocate memory from system heap. | |
| 1153 This is a wrapper around <literal>malloc()</literal> with logging support. | |
| 1154 Allocation error and debugging information is logged to <literal>log</literal> | |
| 1155 </listitem> | |
| 1156 | |
| 1157 <listitem> | |
| 1158 <literal>ngx_calloc(size, log)</literal> - same as | |
| 1159 <literal>ngx_alloc()</literal>, but memory is filled with zeroes after | |
| 1160 allocation | |
| 1161 </listitem> | |
| 1162 | |
| 1163 <listitem> | |
| 1164 <literal>ngx_memalign(alignment, size, log)</literal> - allocate aligned memory | |
| 1165 from system heap. This is a wrapper around <literal>posix_memalign()</literal> | |
| 1166 on those platforms which provide it. | |
| 1167 Otherwise implementation falls back to <literal>ngx_alloc()</literal> which | |
| 1168 provides maximum alignment | |
| 1169 </listitem> | |
| 1170 | |
| 1171 <listitem> | |
| 1172 <literal>ngx_free(p)</literal> - free allocated memory. | |
| 1173 This is a wrapper around <literal>free()</literal> | |
| 1174 </listitem> | |
| 1175 | |
| 1176 </list> | |
| 1177 </para> | |
| 1178 | |
| 1179 </section> | |
| 1180 | |
| 1181 | |
| 1182 <section name="Pool" id="pool"> | |
| 1183 | |
| 1184 <para> | |
| 1185 Most nginx allocations are done in pools. Memory allocated in an nginx pool is | |
| 1186 freed automatically when the pool in destroyed. This provides good | |
| 1187 allocation performance and makes memory control easy. | |
| 1188 </para> | |
| 1189 | |
| 1190 <para> | |
| 1191 A pool internally allocates objects in continuous blocks of memory. Once a | |
| 1192 block is full, a new one is allocated and added to the pool memory | |
| 1193 block list. When a large allocation is requested which does not fit into | |
| 1194 a block, such allocation is forwarded to the system allocator and the | |
| 1195 returned pointer is stored in the pool for further deallocation. | |
| 1196 </para> | |
| 1197 | |
| 1198 <para> | |
| 1199 Nginx pool has the type <literal>ngx_pool_t</literal>. | |
| 1200 The following operations are supported: | |
| 1201 </para> | |
| 1202 | |
| 1203 <para> | |
| 1204 <list type="bullet"> | |
| 1205 | |
| 1206 <listitem> | |
| 1207 <literal>ngx_create_pool(size, log)</literal> - create a pool with given | |
| 1208 block size. The pool object returned is allocated in the pool as well. | |
| 1209 </listitem> | |
| 1210 | |
| 1211 <listitem> | |
| 1212 <literal>ngx_destroy_pool(pool)</literal> - free all pool memory, including | |
| 1213 the pool object itself. | |
| 1214 </listitem> | |
| 1215 | |
| 1216 <listitem> | |
| 1217 <literal>ngx_palloc(pool, size)</literal> - allocate aligned memory from pool | |
| 1218 </listitem> | |
| 1219 | |
| 1220 <listitem> | |
| 1221 <literal>ngx_pcalloc(pool, size)</literal> - allocated aligned memory | |
| 1222 from pool and fill it with zeroes | |
| 1223 </listitem> | |
| 1224 | |
| 1225 <listitem> | |
| 1226 <literal>ngx_pnalloc(pool, size)</literal> - allocate unaligned memory from pool. | |
| 1227 Mostly used for allocating strings | |
| 1228 </listitem> | |
| 1229 | |
| 1230 <listitem> | |
| 1231 <literal>ngx_pfree(pool, p)</literal> - free memory, previously allocated | |
| 1232 in the pool. | |
| 1233 Only allocations, forwarded to the system allocator, can be freed. | |
| 1234 </listitem> | |
| 1235 | |
| 1236 </list> | |
| 1237 </para> | |
| 1238 | |
| 1239 <programlisting> | |
| 1240 u_char *p; | |
| 1241 ngx_str_t *s; | |
| 1242 ngx_pool_t *pool; | |
| 1243 | |
| 1244 pool = ngx_create_pool(1024, log); | |
| 1245 if (pool == NULL) { /* error */ } | |
| 1246 | |
| 1247 s = ngx_palloc(pool, sizeof(ngx_str_t)); | |
| 1248 if (s == NULL) { /* error */ } | |
| 1249 ngx_str_set(s, “foo”); | |
| 1250 | |
| 1251 p = ngx_pnalloc(pool, 3); | |
| 1252 if (p == NULL) { /* error */ } | |
| 1253 ngx_memcpy(p, “foo”, 3); | |
| 1254 </programlisting> | |
| 1255 | |
| 1256 <para> | |
| 1257 Since chain links <literal>ngx_chain_t</literal> are actively used in nginx, | |
| 1258 nginx pool provides a way to reuse them. | |
| 1259 The <literal>chain</literal> field of <literal>ngx_pool_t</literal> keeps a | |
| 1260 list of previously allocated links ready for reuse. For efficient allocation of | |
| 1261 a chain link in a pool, the function | |
| 1262 <literal>ngx_alloc_chain_link(pool)</literal> should be used. | |
| 1263 This function looks up a free chain link in the pool list and only if it's | |
| 1264 empty allocates a new one. To free a link <literal>ngx_free_chain(pool, cl)</literal> | |
| 1265 should be called. | |
| 1266 </para> | |
| 1267 | |
| 1268 <para> | |
| 1269 Cleanup handlers can be registered in a pool. | |
| 1270 Cleanup handler is a callback with an argument which is called when pool is | |
| 1271 destroyed. | |
| 1272 Pool is usually tied with a specific nginx object (like HTTP request) and | |
| 1273 destroyed in the end of that object’s lifetime, releasing the object itself. | |
| 1902 | 1274 Registering a pool cleanup is a convenient way to release resources, close file |
| 1899 | 1275 descriptors or make final adjustments to shared data, associated with the main |
| 1276 object. | |
| 1277 </para> | |
| 1278 | |
| 1279 <para> | |
| 1280 A pool cleanup is registered by calling <literal>ngx_pool_cleanup_add(pool, | |
| 1281 size)</literal> which returns <literal>ngx_pool_cleanup_t</literal> pointer to | |
| 1282 be filled by the caller. The <literal>size</literal> argument allows allocating | |
| 1283 context for the cleanup handler. | |
| 1284 </para> | |
| 1285 | |
| 1286 | |
| 1287 <programlisting> | |
| 1288 ngx_pool_cleanup_t *cln; | |
| 1289 | |
| 1290 cln = ngx_pool_cleanup_add(pool, 0); | |
| 1291 if (cln == NULL) { /* error */ } | |
| 1292 | |
| 1293 cln->handler = ngx_my_cleanup; | |
| 1294 cln->data = “foo”; | |
| 1295 | |
| 1296 ... | |
| 1297 | |
| 1298 static void | |
| 1299 ngx_my_cleanup(void *data) | |
| 1300 { | |
| 1301 u_char *msg = data; | |
| 1302 | |
| 1303 ngx_do_smth(msg); | |
| 1304 } | |
| 1305 </programlisting> | |
| 1306 | |
| 1307 </section> | |
| 1308 | |
| 1309 | |
| 1310 <section name="Shared memory" id="shared_memory"> | |
| 1311 | |
| 1312 <para> | |
| 1313 Shared memory is used by nginx to share common data between processes. | |
| 1314 Function <literal>ngx_shared_memory_add(cf, name, size, tag)</literal> adds a | |
| 1315 new shared memory entry <literal>ngx_shm_zone_t</literal> to the cycle. The | |
| 1316 function receives <literal>name</literal> and <literal>size</literal> of the | |
| 1317 zone. | |
| 1318 Each shared zone must have a unique name. | |
| 1319 If a shared zone entry with the provided name exists, the old zone entry is | |
| 1320 reused, if its tag value matches too. | |
| 1321 Mismatched tag is considered an error. | |
| 1322 Usually, the address of the module structure is passed as tag, making it | |
| 1323 possible to reuse shared zones by name within one nginx module. | |
| 1324 </para> | |
| 1325 | |
| 1326 <para> | |
| 1327 The shared memory entry structure <literal>ngx_shm_zone_t</literal> has the | |
| 1328 following fields: | |
| 1329 </para> | |
| 1330 | |
| 1331 <para> | |
| 1332 <list type="bullet"> | |
| 1333 | |
| 1334 <listitem> | |
| 1335 <literal>init</literal> - initialization callback, called after shared zone is | |
| 1336 mapped to actual memory | |
| 1337 </listitem> | |
| 1338 | |
| 1339 <listitem> | |
| 1340 <literal>data</literal> - data context, used to pass arbitrary data to the | |
| 1341 <literal>init</literal> callback | |
| 1342 </listitem> | |
| 1343 | |
| 1344 <listitem> | |
| 1345 <literal>noreuse</literal> - flag, disabling shared zone reuse from the | |
| 1346 old cycle | |
| 1347 </listitem> | |
| 1348 | |
| 1349 <listitem> | |
| 1350 <literal>tag</literal> - shared zone tag | |
| 1351 </listitem> | |
| 1352 | |
| 1353 <listitem> | |
| 1354 <literal>shm</literal> - platform-specific object of type | |
| 1355 <literal>ngx_shm_t</literal>, having at least the following fields: | |
| 1356 <list type="bullet"> | |
| 1357 | |
| 1358 <listitem> | |
| 1359 <literal>addr</literal> - mapped shared memory address, initially NULL | |
| 1360 </listitem> | |
| 1361 | |
| 1362 <listitem> | |
| 1363 <literal>size</literal> - shared memory size | |
| 1364 </listitem> | |
| 1365 | |
| 1366 <listitem> | |
| 1367 <literal>name</literal> - shared memory name | |
| 1368 </listitem> | |
| 1369 | |
| 1370 <listitem> | |
| 1371 <literal>log</literal> - shared memory log | |
| 1372 </listitem> | |
| 1373 | |
| 1374 <listitem> | |
| 1375 <literal>exists</literal> - flag, showing that shared memory was inherited | |
| 1376 from the master process (Windows-specific) | |
| 1377 </listitem> | |
| 1378 | |
| 1379 </list> | |
| 1380 </listitem> | |
| 1381 | |
| 1382 </list> | |
| 1383 </para> | |
| 1384 | |
| 1385 <para> | |
| 1386 Shared zone entries are mapped to actual memory in | |
| 1387 <literal>ngx_init_cycle()</literal> after configuration is parsed. | |
| 1388 On POSIX systems, <literal>mmap()</literal> syscall is used to create shared | |
| 1389 anonymous mapping. | |
| 1390 On Windows, <literal>CreateFileMapping()/MapViewOfFileEx()</literal> pair is | |
| 1391 used. | |
| 1392 </para> | |
| 1393 | |
| 1394 <para> | |
| 1395 For allocating in shared memory, nginx provides slab pool | |
| 1396 <literal>ngx_slab_pool_t</literal>. | |
| 1397 In each nginx shared zone, a slab pool is automatically created for allocating | |
| 1398 memory in that zone. | |
| 1399 The pool is located in the beginning of the shared zone and can be accessed by | |
| 1400 the expression <literal>(ngx_slab_pool_t *) shm_zone->shm.addr</literal>. | |
| 1401 Allocation in shared zone is done by calling one of the functions | |
| 1402 <literal>ngx_slab_alloc(pool, size)/ngx_slab_calloc(pool, size)</literal>. | |
| 1403 Memory is freed by calling <literal>ngx_slab_free(pool, p)</literal>. | |
| 1404 </para> | |
| 1405 | |
| 1406 <para> | |
| 1407 Slab pool divides all shared zone into pages. | |
| 1408 Each page is used for allocating objects of the same size. | |
| 1409 Only the sizes which are powers of 2, and not less than 8, are considered. | |
| 1410 Other sizes are rounded up to one of these values. | |
| 1411 For each page, a bitmask is kept, showing which blocks within that page are in | |
| 1412 use and which are free for allocation. | |
| 1413 For sizes greater than half-page (usually, 2048 bytes), allocation is done by | |
| 1414 entire pages. | |
| 1415 </para> | |
| 1416 | |
| 1417 <para> | |
| 1418 To protect data in shared memory from concurrent access, mutex is available in | |
| 1419 the <literal>mutex</literal> field of <literal>ngx_slab_pool_t</literal>. | |
| 1420 The mutex is used by the slab pool while allocating and freeing memory. | |
| 1421 However, it can be used to protect any other user data structures, | |
| 1422 allocated in the shared zone. | |
| 1423 Locking is done by calling | |
| 1424 <literal>ngx_shmtx_lock(&shpool->mutex)</literal>, unlocking is done by | |
| 1425 calling <literal>ngx_shmtx_unlock(&shpool->mutex)</literal>. | |
| 1426 </para> | |
| 1427 | |
| 1428 | |
| 1429 <programlisting> | |
| 1430 ngx_str_t name; | |
| 1431 ngx_foo_ctx_t *ctx; | |
| 1432 ngx_shm_zone_t *shm_zone; | |
| 1433 | |
| 1434 ngx_str_set(&name, "foo"); | |
| 1435 | |
| 1436 /* allocate shared zone context */ | |
| 1437 ctx = ngx_pcalloc(cf->pool, sizeof(ngx_foo_ctx_t)); | |
| 1438 if (ctx == NULL) { | |
| 1439 /* error */ | |
| 1440 } | |
| 1441 | |
| 1442 /* add an entry for 65k shared zone */ | |
| 1443 shm_zone = ngx_shared_memory_add(cf, &name, 65536, &ngx_foo_module); | |
| 1444 if (shm_zone == NULL) { | |
| 1445 /* error */ | |
| 1446 } | |
| 1447 | |
| 1448 /* register init callback and context */ | |
| 1449 shm_zone->init = ngx_foo_init_zone; | |
| 1450 shm_zone->data = ctx; | |
| 1451 | |
| 1452 | |
| 1453 ... | |
| 1454 | |
| 1455 | |
| 1456 static ngx_int_t | |
| 1457 ngx_foo_init_zone(ngx_shm_zone_t *shm_zone, void *data) | |
| 1458 { | |
| 1459 ngx_foo_ctx_t *octx = data; | |
| 1460 | |
| 1461 size_t len; | |
| 1462 ngx_foo_ctx_t *ctx; | |
| 1463 ngx_slab_pool_t *shpool; | |
| 1464 | |
| 1465 value = shm_zone->data; | |
| 1466 | |
| 1467 if (octx) { | |
| 1468 /* reusing a shared zone from old cycle */ | |
| 1469 ctx->value = octx->value; | |
| 1470 return NGX_OK; | |
| 1471 } | |
| 1472 | |
| 1473 shpool = (ngx_slab_pool_t *) shm_zone->shm.addr; | |
| 1474 | |
| 1475 if (shm_zone->shm.exists) { | |
| 1476 /* initialize shared zone context in Windows nginx worker */ | |
| 1477 ctx->value = shpool->data; | |
| 1478 return NGX_OK; | |
| 1479 } | |
| 1480 | |
| 1481 /* initialize shared zone */ | |
| 1482 | |
| 1483 ctx->value = ngx_slab_alloc(shpool, sizeof(ngx_uint_t)); | |
| 1484 if (ctx->value == NULL) { | |
| 1485 return NGX_ERROR; | |
| 1486 } | |
| 1487 | |
| 1488 shpool->data = ctx->value; | |
| 1489 | |
| 1490 return NGX_OK; | |
| 1491 } | |
| 1492 </programlisting> | |
| 1493 | |
| 1494 </section> | |
| 1495 | |
| 1496 | |
| 1497 </section> | |
| 1498 | |
| 1499 | |
| 1500 <section name="Logging" id="logging"> | |
| 1501 | |
| 1502 <para> | |
| 1503 For logging nginx code uses <literal>ngx_log_t</literal> objects. | |
| 1504 Nginx logger provides support for several types of output: | |
| 1505 | |
| 1506 <list type="bullet"> | |
| 1507 | |
| 1508 <listitem> | |
| 1509 stderr - logging to standard error output | |
| 1510 </listitem> | |
| 1511 | |
| 1512 <listitem> | |
| 1513 file - logging to file | |
| 1514 </listitem> | |
| 1515 | |
| 1516 <listitem> | |
| 1517 syslog - logging to syslog | |
| 1518 </listitem> | |
| 1519 | |
| 1520 <listitem> | |
| 1521 memory - logging to internal memory storage for development purposes. | |
| 1522 The memory could be accessed later with debugger | |
| 1523 </listitem> | |
| 1524 | |
| 1525 </list> | |
| 1526 </para> | |
| 1527 | |
| 1528 <para> | |
| 1529 A logger instance may actually be a chain of loggers, linked to each other with | |
| 1530 the <literal>next</literal> field. | |
| 1531 Each message is written to all loggers in chain. | |
| 1532 </para> | |
| 1533 | |
| 1534 <para> | |
| 1535 Each logger has an error level which limits the messages written to that log. | |
| 1536 The following error levels are supported by nginx: | |
| 1537 </para> | |
| 1538 | |
| 1539 <para> | |
| 1540 <list type="bullet"> | |
| 1541 | |
| 1542 <listitem> | |
| 1543 <literal>NGX_LOG_EMERG</literal> | |
| 1544 </listitem> | |
| 1545 | |
| 1546 <listitem> | |
| 1547 <literal>NGX_LOG_ALERT</literal> | |
| 1548 </listitem> | |
| 1549 | |
| 1550 <listitem> | |
| 1551 <literal>NGX_LOG_CRIT</literal> | |
| 1552 </listitem> | |
| 1553 | |
| 1554 <listitem> | |
| 1555 <literal>NGX_LOG_ERR</literal> | |
| 1556 </listitem> | |
| 1557 | |
| 1558 <listitem> | |
| 1559 <literal>NGX_LOG_WARN</literal> | |
| 1560 </listitem> | |
| 1561 | |
| 1562 <listitem> | |
| 1563 <literal>NGX_LOG_NOTICE</literal> | |
| 1564 </listitem> | |
| 1565 | |
| 1566 <listitem> | |
| 1567 <literal>NGX_LOG_INFO</literal> | |
| 1568 </listitem> | |
| 1569 | |
| 1570 <listitem> | |
| 1571 <literal>NGX_LOG_DEBUG</literal> | |
| 1572 </listitem> | |
| 1573 | |
| 1574 </list> | |
| 1575 </para> | |
| 1576 | |
| 1577 <para> | |
| 1578 For debug logging, debug mask is checked as well. The following debug masks | |
| 1579 exist: | |
| 1580 </para> | |
| 1581 | |
| 1582 <para> | |
| 1583 <list type="bullet"> | |
| 1584 | |
| 1585 <listitem> | |
| 1586 <literal>NGX_LOG_DEBUG_CORE</literal> | |
| 1587 </listitem> | |
| 1588 | |
| 1589 <listitem> | |
| 1590 <literal>NGX_LOG_DEBUG_ALLOC</literal> | |
| 1591 </listitem> | |
| 1592 | |
| 1593 <listitem> | |
| 1594 <literal>NGX_LOG_DEBUG_MUTEX</literal> | |
| 1595 </listitem> | |
| 1596 | |
| 1597 <listitem> | |
| 1598 <literal>NGX_LOG_DEBUG_EVENT</literal> | |
| 1599 </listitem> | |
| 1600 | |
| 1601 <listitem> | |
| 1602 <literal>NGX_LOG_DEBUG_HTTP</literal> | |
| 1603 </listitem> | |
| 1604 | |
| 1605 <listitem> | |
| 1606 <literal>NGX_LOG_DEBUG_MAIL</literal> | |
| 1607 </listitem> | |
| 1608 | |
| 1609 <listitem> | |
| 1610 <literal>NGX_LOG_DEBUG_STREAM</literal> | |
| 1611 </listitem> | |
| 1612 | |
| 1613 </list> | |
| 1614 </para> | |
| 1615 | |
| 1616 <para> | |
| 1617 Normally, loggers are created by existing nginx code from | |
| 1618 <literal>error_log</literal> directives and are available at nearly every stage | |
| 1619 of processing in cycle, configuration, client connection and other objects. | |
| 1620 </para> | |
| 1621 | |
| 1622 <para> | |
| 1623 Nginx provides the following logging macros: | |
| 1624 </para> | |
| 1625 | |
| 1626 <para> | |
| 1627 <list type="bullet"> | |
| 1628 | |
| 1629 <listitem> | |
| 1630 <literal>ngx_log_error(level, log, err, fmt, ...)</literal> - error logging | |
| 1631 </listitem> | |
| 1632 | |
| 1633 <listitem> | |
| 1634 <literal>ngx_log_debug0(level, log, err, fmt)</literal>, | |
| 1635 <literal>ngx_log_debug1(level, log, err, fmt, arg1)</literal> etc - debug | |
| 1636 logging, up to 8 formatting arguments are supported | |
| 1637 </listitem> | |
| 1638 | |
| 1639 </list> | |
| 1640 </para> | |
| 1641 | |
| 1642 <para> | |
| 1643 A log message is formatted in a buffer of size | |
| 1644 <literal>NGX_MAX_ERROR_STR</literal> (currently, 2048 bytes) on stack. | |
| 1645 The message is prepended with error level, process PID, connection id (stored | |
| 1646 in <literal>log->connection</literal>) and system error text. | |
| 1647 For non-debug messages <literal>log->handler</literal> is called as well to | |
| 1648 prepend more specific information to the log message. | |
| 1649 HTTP module sets <literal>ngx_http_log_error()</literal> function as log | |
| 1650 handler to log client and server addresses, current action (stored in | |
| 1651 <literal>log->action</literal>), client request line, server name etc. | |
| 1652 </para> | |
| 1653 | |
| 1654 <para> | |
| 1655 Example: | |
| 1656 </para> | |
| 1657 | |
| 1658 | |
| 1659 <programlisting> | |
| 1660 /* specify what is currently done */ | |
| 1661 log->action = "sending mp4 to client”; | |
| 1662 | |
| 1663 /* error and debug log */ | |
| 1664 ngx_log_error(NGX_LOG_INFO, c->log, 0, "client prematurely | |
| 1665 closed connection”); | |
| 1666 | |
| 1667 ngx_log_debug2(NGX_LOG_DEBUG_HTTP, mp4->file.log, 0, | |
| 1668 "mp4 start:%ui, length:%ui”, mp4->start, mp4->length); | |
| 1669 </programlisting> | |
| 1670 | |
| 1671 <para> | |
| 1672 Logging result: | |
| 1673 </para> | |
| 1674 | |
| 1675 | |
| 1676 <programlisting> | |
| 1677 2016/09/16 22:08:52 [info] 17445#0: *1 client prematurely closed connection while | |
| 1678 sending mp4 to client, client: 127.0.0.1, server: , request: "GET /file.mp4 HTTP/1.1” | |
| 1679 2016/09/16 23:28:33 [debug] 22140#0: *1 mp4 start:0, length:10000 | |
| 1680 </programlisting> | |
| 1681 | |
| 1682 </section> | |
| 1683 | |
| 1684 | |
| 1685 <section name="Cycle" id="cycle"> | |
| 1686 | |
| 1687 <para> | |
| 1688 Cycle object keeps nginx runtime context, created from a specific | |
| 1689 configuration. | |
| 1690 The type of the cycle is <literal>ngx_cycle_t</literal>. | |
| 1691 Upon configuration reload a new cycle is created from the new version of nginx | |
| 1692 configuration. | |
| 1693 The old cycle is usually deleted after a new one is successfully created. | |
| 1694 Currently active cycle is held in the <literal>ngx_cycle</literal> global | |
| 1695 variable and is inherited by newly started nginx workers. | |
| 1696 </para> | |
| 1697 | |
| 1698 <para> | |
| 1699 A cycle is created by the function <literal>ngx_init_cycle()</literal>. | |
| 1700 The function receives the old cycle as the argument. | |
| 1701 It's used to locate the configuration file and inherit as much resources as | |
| 1702 possible from the old cycle to keep nginx running smoothly. | |
| 1703 When nginx starts, a fake cycle called "init cycle" is created and is then | |
| 1704 replaced by a normal cycle, built from configuration. | |
| 1705 </para> | |
| 1706 | |
| 1707 <para> | |
| 1708 Some members of the cycle: | |
| 1709 </para> | |
| 1710 | |
| 1711 <para> | |
| 1712 <list type="bullet"> | |
| 1713 | |
| 1714 <listitem> | |
| 1715 <literal>pool</literal> - cycle pool. Created for each new cycle | |
| 1716 </listitem> | |
| 1717 | |
| 1718 <listitem> | |
| 1719 <literal>log</literal> - cycle log. Initially, this log is inherited from the | |
| 1720 old cycle. | |
| 1721 After reading configuration, this member is set to point to | |
| 1722 <literal>new_log</literal> | |
| 1723 </listitem> | |
| 1724 | |
| 1725 <listitem> | |
| 1726 <literal>new_log</literal> - cycle log, created by the configuration. | |
| 1727 It's affected by the root scope <literal>error_log</literal> directive | |
| 1728 </listitem> | |
| 1729 | |
| 1730 <listitem> | |
| 1731 <literal>connections</literal>, <literal>connections_n</literal> - per-worker | |
| 1732 array of connections of type <literal>ngx_connection_t</literal>, created by | |
| 1733 the event module while initializing each nginx worker. | |
| 1734 The number of connections is set by the <literal>worker_connections</literal> | |
| 1735 directive | |
| 1736 </listitem> | |
| 1737 | |
| 1738 <listitem> | |
| 1739 <literal>free_connections</literal>, | |
| 1740 <literal>free_connections_n</literal> - the and number of currently available | |
| 1741 connections. | |
| 1742 If no connections are available, nginx worker refuses to accept new clients | |
| 1743 </listitem> | |
| 1744 | |
| 1745 <listitem> | |
| 1746 <literal>files</literal>, <literal>files_n</literal> - array for mapping file | |
| 1747 descriptors to nginx connections. | |
| 1748 This mapping is used by the event modules, having the | |
| 1749 <literal>NGX_USE_FD_EVENT</literal> flag (currently, it's poll and devpoll) | |
| 1750 </listitem> | |
| 1751 | |
| 1752 <listitem> | |
| 1753 <literal>conf_ctx</literal> - array of core module configurations. | |
| 1754 The configurations are created and filled while reading nginx configuration | |
| 1755 files | |
| 1756 </listitem> | |
| 1757 | |
| 1758 <listitem> | |
| 1759 <literal>modules</literal>, <literal>modules_n</literal> - array of modules | |
| 1760 <literal>ngx_module_t</literal>, both static and dynamic, loaded by current | |
| 1761 configuration | |
| 1762 </listitem> | |
| 1763 | |
| 1764 <listitem> | |
| 1765 <literal>listening</literal> - array of listening objects | |
| 1766 <literal>ngx_listening_t</literal>. | |
| 1767 Listening objects are normally added by the the <literal>listen</literal> | |
| 1768 directive of different modules which call the | |
| 1769 <literal>ngx_create_listening()</literal> function. | |
| 1770 Based on listening objects, listen sockets are created by nginx | |
| 1771 </listitem> | |
| 1772 | |
| 1773 <listitem> | |
| 1774 <literal>paths</literal> - array of paths <literal>ngx_path_t</literal>. | |
| 1775 Paths are added by calling the function <literal>ngx_add_path()</literal> from | |
| 1776 modules which are going to operate on certain directories. | |
| 1777 These directories are created by nginx after reading configuration, if missing. | |
| 1778 Moreover, two handlers can be added for each path: | |
| 1779 | |
| 1780 <list type="bullet"> | |
| 1781 | |
| 1782 <listitem> | |
| 1783 path loader - executed only once in 60 seconds after starting or reloading | |
| 1784 nginx. Normally, reads the directory and stores data in nginx shared | |
| 1785 memory. The handler is called from a dedicated nginx process "nginx | |
| 1786 cache loader" | |
| 1787 </listitem> | |
| 1788 | |
| 1789 <listitem> | |
| 1790 path manager - executed periodically. Normally, removes old files from the | |
| 1791 directory and reflects these changes in nginx memory. The handler is | |
| 1792 called from a dedicated nginx process "nginx cache manager" | |
| 1793 </listitem> | |
| 1794 | |
| 1795 </list> | |
| 1796 </listitem> | |
| 1797 | |
| 1798 <listitem> | |
| 1799 <literal>open_files</literal> - list of <literal>ngx_open_file_t</literal> | |
| 1800 objects. | |
| 1801 An open file object is created by calling the function | |
| 1802 <literal>ngx_conf_open_file()</literal>. | |
| 1803 After reading configuration nginx opens all files from the | |
| 1804 <literal>open_files</literal> list and stores file descriptors in the | |
| 1805 <literal>fd</literal> field of each open file object. | |
| 1806 The files are opened in append mode and created if missing. | |
| 1807 The files from this list are reopened by nginx workers upon receiving the | |
| 1808 reopen signal (usually it's <literal>USR1</literal>). | |
| 1809 In this case the <literal>fd</literal> fields are changed to new descriptors. | |
| 1810 The open files are currently used for logging | |
| 1811 </listitem> | |
| 1812 | |
| 1813 <listitem> | |
| 1814 <literal>shared_memory</literal> - list of shared memory zones, each added by | |
| 1815 calling the <literal>ngx_shared_memory_add()</literal> function. | |
| 1816 Shared zones are mapped to the same address range in all nginx processes and | |
| 1817 are used to share common data, for example HTTP cache in-memory tree | |
| 1818 </listitem> | |
| 1819 | |
| 1820 </list> | |
| 1821 </para> | |
| 1822 | |
| 1823 </section> | |
| 1824 | |
| 1825 <section name="Buffer" id="buffer"> | |
| 1826 | |
| 1827 <para> | |
| 1828 For input/output operations, nginx provides the buffer type | |
| 1829 <literal>ngx_buf_t</literal>. | |
| 1830 Normally, it's used to hold data to be written to a destination or read from a | |
| 1831 source. | |
| 1832 Buffer can reference data in memory and in file. | |
| 1833 Technically it's possible that a buffer references both at the same time. | |
| 1834 Memory for the buffer is allocated separately and is not related to the buffer | |
| 1835 structure <literal>ngx_buf_t</literal>. | |
| 1836 </para> | |
| 1837 | |
| 1838 <para> | |
| 1839 The structure <literal>ngx_buf_t</literal> has the following fields: | |
| 1840 </para> | |
| 1841 | |
| 1842 <para> | |
| 1843 <list type="bullet"> | |
| 1844 | |
| 1845 <listitem> | |
| 1846 <literal>start</literal>, <literal>end</literal> - the boundaries of memory | |
| 1847 block, allocated for the buffer | |
| 1848 </listitem> | |
| 1849 | |
| 1850 <listitem> | |
| 1851 <literal>pos</literal>, <literal>last</literal> - memory buffer boundaries, | |
| 1852 normally a subrange of <literal>start</literal> .. <literal>end</literal> | |
| 1853 </listitem> | |
| 1854 | |
| 1855 <listitem> | |
| 1856 <literal>file_pos</literal>, <literal>file_last</literal> - file buffer | |
| 1857 boundaries, these are offsets from the beginning of the file | |
| 1858 </listitem> | |
| 1859 | |
| 1860 <listitem> | |
| 1861 <literal>tag</literal> - unique value, used to distinguish buffers, created by | |
| 1862 different nginx module, usually, for the purpose of buffer reuse | |
| 1863 </listitem> | |
| 1864 | |
| 1865 <listitem> | |
| 1866 <literal>file</literal> - file object | |
| 1867 </listitem> | |
| 1868 | |
| 1869 <listitem> | |
| 1870 <literal>temporary</literal> - flag, meaning that the buffer references | |
| 1871 writable memory | |
| 1872 </listitem> | |
| 1873 | |
| 1874 <listitem> | |
| 1875 <literal>memory</literal> - flag, meaning that the buffer references read-only | |
| 1876 memory | |
| 1877 </listitem> | |
| 1878 | |
| 1879 <listitem> | |
| 1880 <literal>in_file</literal> - flag, meaning that current buffer references data | |
| 1881 in a file | |
| 1882 </listitem> | |
| 1883 | |
| 1884 <listitem> | |
| 1885 <literal>flush</literal> - flag, meaning that all data prior to this buffer | |
| 1886 should be flushed | |
| 1887 </listitem> | |
| 1888 | |
| 1889 <listitem> | |
| 1890 <literal>recycled</literal> - flag, meaning that the buffer can be reused and | |
| 1891 should be consumed as soon as possible | |
| 1892 </listitem> | |
| 1893 | |
| 1894 <listitem> | |
| 1895 <literal>sync</literal> - flag, meaning that the buffer carries no data or | |
| 1896 special signal like <literal>flush</literal> or <literal>last_buf</literal>. | |
| 1897 Normally, such buffers are considered an error by nginx. This flags allows | |
| 1898 skipping the error checks | |
| 1899 </listitem> | |
| 1900 | |
| 1901 <listitem> | |
| 1902 <literal>last_buf</literal> - flag, meaning that current buffer is the last in | |
| 1903 output | |
| 1904 </listitem> | |
| 1905 | |
| 1906 <listitem> | |
| 1907 <literal>last_in_chain</literal> - flag, meaning that there's no more data | |
| 1908 buffers in a (sub)request | |
| 1909 </listitem> | |
| 1910 | |
| 1911 <listitem> | |
| 1912 <literal>shadow</literal> - reference to another buffer, related to the current | |
| 1913 buffer. Usually current buffer uses data from the shadow buffer. Once current | |
| 1914 buffer is consumed, the shadow buffer should normally also be marked as | |
| 1915 consumed | |
| 1916 </listitem> | |
| 1917 | |
| 1918 <listitem> | |
| 1919 <literal>last_shadow</literal> - flag, meaning that current buffer is the last | |
| 1920 buffer, referencing a particular shadow buffer | |
| 1921 </listitem> | |
| 1922 | |
| 1923 <listitem> | |
| 1924 <literal>temp_file</literal> - flag, meaning that the buffer is in a temporary | |
| 1925 file | |
| 1926 </listitem> | |
| 1927 | |
| 1928 </list> | |
| 1929 </para> | |
| 1930 | |
| 1931 <para> | |
| 1932 For input and output buffers are linked in chains. | |
| 1933 Chain is a sequence of chain links <literal>ngx_chain_t</literal>, defined as | |
| 1934 follows: | |
| 1935 </para> | |
| 1936 | |
| 1937 | |
| 1938 <programlisting> | |
| 1939 typedef struct ngx_chain_s ngx_chain_t; | |
| 1940 | |
| 1941 struct ngx_chain_s { | |
| 1942 ngx_buf_t *buf; | |
| 1943 ngx_chain_t *next; | |
| 1944 }; | |
| 1945 </programlisting> | |
| 1946 | |
| 1947 <para> | |
| 1948 Each chain link keeps a reference to its buffer and a reference to the next | |
| 1949 chain link. | |
| 1950 </para> | |
| 1951 | |
| 1952 <para> | |
| 1953 Example of using buffers and chains: | |
| 1954 </para> | |
| 1955 | |
| 1956 | |
| 1957 <programlisting> | |
| 1958 ngx_chain_t * | |
| 1959 ngx_get_my_chain(ngx_pool_t *pool) | |
| 1960 { | |
| 1961 ngx_buf_t *b; | |
| 1962 ngx_chain_t *out, *cl, **ll; | |
| 1963 | |
| 1964 /* first buf */ | |
| 1965 cl = ngx_alloc_chain_link(pool); | |
| 1966 if (cl == NULL) { /* error */ } | |
| 1967 | |
| 1968 b = ngx_calloc_buf(pool); | |
| 1969 if (b == NULL) { /* error */ } | |
| 1970 | |
| 1971 b->start = (u_char *) "foo"; | |
| 1972 b->pos = b->start; | |
| 1973 b->end = b->start + 3; | |
| 1974 b->last = b->end; | |
| 1975 b->memory = 1; /* read-only memory */ | |
| 1976 | |
| 1977 cl->buf = b; | |
| 1978 out = cl; | |
| 1979 ll = &cl->next; | |
| 1980 | |
| 1981 /* second buf */ | |
| 1982 cl = ngx_alloc_chain_link(pool); | |
| 1983 if (cl == NULL) { /* error */ } | |
| 1984 | |
| 1985 b = ngx_create_temp_buf(pool, 3); | |
| 1986 if (b == NULL) { /* error */ } | |
| 1987 | |
| 1988 b->last = ngx_cpymem(b->last, "foo", 3); | |
| 1989 | |
| 1990 cl->buf = b; | |
| 1991 cl->next = NULL; | |
| 1992 *ll = cl; | |
| 1993 | |
| 1994 return out; | |
| 1995 } | |
| 1996 </programlisting> | |
| 1997 | |
| 1998 </section> | |
| 1999 | |
| 2000 | |
| 2001 <section name="Networking" id="networking"> | |
| 2002 | |
| 2003 | |
| 2004 <!-- | |
| 2005 <section name="Network data types" id="network_data_types"> | |
| 2006 | |
| 2007 <para> | |
| 2008 TBD: ngx_addr_t, ngx_url_t, ngx_socket_t, ngx_sockaddr_t, parse url, parse | |
| 2009 address... | |
| 2010 </para> | |
| 2011 | |
| 2012 </section> | |
| 2013 --> | |
| 2014 | |
| 2015 <section name="Connection" id="connection"> | |
| 2016 | |
| 2017 <para> | |
| 2018 Connection type <literal>ngx_connection_t</literal> is a wrapper around a | |
| 2019 socket descriptor. Some of the structure fields are: | |
| 2020 </para> | |
| 2021 | |
| 2022 <para> | |
| 2023 <list type="bullet"> | |
| 2024 | |
| 2025 <listitem> | |
| 2026 <literal>fd</literal> - socket descriptor | |
| 2027 </listitem> | |
| 2028 | |
| 2029 <listitem> | |
| 2030 <literal>data</literal> - arbitrary connection context. | |
| 2031 Normally, a pointer to a higher level object, built on top of the connection, | |
| 2032 like HTTP request or Stream session | |
| 2033 </listitem> | |
| 2034 | |
| 2035 <listitem> | |
| 2036 <literal>read</literal>, <literal>write</literal> - read and write events for | |
| 2037 the connection | |
| 2038 </listitem> | |
| 2039 | |
| 2040 <listitem> | |
| 2041 <literal>recv</literal>, <literal>send</literal>, | |
| 2042 <literal>recv_chain</literal>, <literal>send_chain</literal> - I/O operations | |
| 2043 for the connection | |
| 2044 </listitem> | |
| 2045 | |
| 2046 <listitem> | |
| 2047 <literal>pool</literal> - connection pool | |
| 2048 </listitem> | |
| 2049 | |
| 2050 <listitem> | |
| 2051 <literal>log</literal> - connection log | |
| 2052 </listitem> | |
| 2053 | |
| 2054 <listitem> | |
| 2055 <literal>sockaddr</literal>, <literal>socklen</literal>, | |
| 2056 <literal>addr_text</literal> - remote socket address in binary and text forms | |
| 2057 </listitem> | |
| 2058 | |
| 2059 <listitem> | |
| 2060 <literal>local_sockaddr</literal>, <literal>local_socklen</literal> - local | |
| 2061 socket address in binary form. | |
| 2062 Initially, these fields are empty. | |
| 2063 Function <literal>ngx_connection_local_sockaddr()</literal> should be used to | |
| 2064 get socket local address | |
| 2065 </listitem> | |
| 2066 | |
| 2067 <listitem> | |
| 2068 <literal>proxy_protocol_addr</literal>, <literal>proxy_protocol_port</literal> | |
| 2069 - PROXY protocol client address and port, if PROXY protocol is enabled for the | |
| 2070 connection | |
| 2071 </listitem> | |
| 2072 | |
| 2073 <listitem> | |
| 2074 <literal>ssl</literal> - nginx connection SSL context | |
| 2075 </listitem> | |
| 2076 | |
| 2077 <listitem> | |
| 2078 <literal>reusable</literal> - flag, meaning, that the connection is at the | |
| 2079 state, when it can be reused | |
| 2080 </listitem> | |
| 2081 | |
| 2082 <listitem> | |
| 2083 <literal>close</literal> - flag, meaning, that the connection is being reused | |
| 2084 and should be closed | |
| 2085 </listitem> | |
| 2086 | |
| 2087 </list> | |
| 2088 </para> | |
| 2089 | |
| 2090 <para> | |
| 2091 An nginx connection can transparently encapsulate SSL layer. | |
| 2092 In this case the connection <literal>ssl</literal> field holds a pointer to an | |
| 2093 <literal>ngx_ssl_connection_t</literal> structure, keeping all SSL-related data | |
| 2094 for the connection, including <literal>SSL_CTX</literal> and | |
| 2095 <literal>SSL</literal>. | |
| 2096 The handlers <literal>recv</literal>, <literal>send</literal>, | |
| 2097 <literal>recv_chain</literal>, <literal>send_chain</literal> are set as well to | |
| 2098 SSL functions. | |
| 2099 </para> | |
| 2100 | |
| 2101 <para> | |
| 2102 The number of connections per nginx worker is limited by the | |
| 2103 <literal>worker_connections</literal> value. | |
| 2104 All connection structures are pre-created when a worker starts and stored in | |
| 2105 the <literal>connections</literal> field of the cycle object. | |
| 2106 To reach out for a connection structure, <literal>ngx_get_connection(s, | |
| 2107 log)</literal> function is used. | |
| 2108 The function receives a socket descriptor <literal>s</literal> which needs to | |
| 2109 be wrapped in a connection structure. | |
| 2110 </para> | |
| 2111 | |
| 2112 <para> | |
| 2113 Since the number of connections per worker is limited, nginx provides a | |
| 2114 way to grab connections which are currently in use. | |
| 2115 To enable or disable reuse of a connection, function | |
| 2116 <literal>ngx_reusable_connection(c, reusable)</literal> is called. | |
| 2117 Calling <literal>ngx_reusable_connection(c, 1)</literal> sets the | |
| 2118 <literal>reuse</literal> flag of the connection structure and inserts the | |
| 2119 connection in the <literal>reusable_connections_queue</literal> of the cycle. | |
| 2120 Whenever <literal>ngx_get_connection()</literal> finds out there are no | |
| 2121 available connections in the <literal>free_connections</literal> list of the | |
| 2122 cycle, it calls <literal>ngx_drain_connections()</literal> to release a | |
| 2123 specific number of reusable connections. | |
| 2124 For each such connection, the <literal>close</literal> flag is set and its read | |
| 2125 handler is called which is supposed to free the connection by calling | |
| 2126 <literal>ngx_close_connection(c)</literal> and make it available for reuse. | |
| 2127 To exit the state when a connection can be reused | |
| 2128 <literal>ngx_reusable_connection(c, 0)</literal> is called. | |
| 2129 An example of reusable connections in nginx is HTTP client connections which | |
| 2130 are marked as reusable until some data is received from the client. | |
| 2131 </para> | |
| 2132 | |
| 2133 </section> | |
| 2134 | |
| 2135 | |
| 2136 </section> | |
| 2137 | |
| 2138 | |
| 2139 <section name="Events" id="events"> | |
| 2140 | |
| 2141 | |
| 2142 <section name="Event" id="event"> | |
| 2143 | |
| 2144 <para> | |
| 2145 Event object <literal>ngx_event_t</literal> in nginx provides a way to be | |
| 2146 notified of a specific event happening. | |
| 2147 </para> | |
| 2148 | |
| 2149 <para> | |
| 2150 Some of the fields of the <literal>ngx_event_t</literal> are: | |
| 2151 </para> | |
| 2152 | |
| 2153 <para> | |
| 2154 <list type="bullet"> | |
| 2155 | |
| 2156 <listitem> | |
| 2157 <literal>data</literal> - arbitrary event context, used in event handler, | |
| 2158 usually, a pointer to a connection, tied with the event | |
| 2159 </listitem> | |
| 2160 | |
| 2161 <listitem> | |
| 2162 <literal>handler</literal> - callback function to be invoked when the event | |
| 2163 happens | |
| 2164 </listitem> | |
| 2165 | |
| 2166 <listitem> | |
| 2167 <literal>write</literal> - flag, meaning that this is the write event. | |
| 2168 Used to distinguish between read and write events | |
| 2169 </listitem> | |
| 2170 | |
| 2171 <listitem> | |
| 2172 <literal>active</literal> - flag, meaning that the event is registered for | |
| 2173 receiving I/O notifications, normally from notification mechanisms like epoll, | |
| 2174 kqueue, poll | |
| 2175 </listitem> | |
| 2176 | |
| 2177 <listitem> | |
| 2178 <literal>ready</literal> - flag, meaning that the event has received an | |
| 2179 I/O notification | |
| 2180 </listitem> | |
| 2181 | |
| 2182 <listitem> | |
| 2183 <literal>delayed</literal> - flag, meaning that I/O is delayed due to rate | |
| 2184 limiting | |
| 2185 </listitem> | |
| 2186 | |
| 2187 <listitem> | |
| 2188 <literal>timer</literal> - Red-Black tree node for inserting the event into | |
| 2189 the timer tree | |
| 2190 </listitem> | |
| 2191 | |
| 2192 <listitem> | |
| 2193 <literal>timer_set</literal> - flag, meaning that the event timer is set, | |
| 2194 but not yet expired | |
| 2195 </listitem> | |
| 2196 | |
| 2197 <listitem> | |
| 2198 <literal>timedout</literal> - flag, meaning that the event timer has expired | |
| 2199 </listitem> | |
| 2200 | |
| 2201 <listitem> | |
| 2202 <literal>eof</literal> - read event flag, meaning that the eof has happened | |
| 2203 while reading data | |
| 2204 </listitem> | |
| 2205 | |
| 2206 <listitem> | |
| 2207 <literal>pending_eof</literal> - flag, meaning that the eof is pending on the | |
| 2208 socket, even though there may be some data available before it. | |
| 2209 The flag is delivered via <literal>EPOLLRDHUP</literal> epoll event or | |
| 2210 <literal>EV_EOF</literal> kqueue flag | |
| 2211 </listitem> | |
| 2212 | |
| 2213 <listitem> | |
| 2214 <literal>error</literal> - flag, meaning that an error has happened while | |
| 2215 reading (for read event) or writing (for write event) | |
| 2216 </listitem> | |
| 2217 | |
| 2218 <listitem> | |
| 2219 <literal>cancelable</literal> - timer event flag, meaning that the event | |
| 2220 handler should be called while performing nginx worker graceful shutdown, event | |
| 2221 though event timeout has not yet expired. The flag provides a way to finalize | |
| 2222 certain activities, for example, flush log files | |
| 2223 </listitem> | |
| 2224 | |
| 2225 <listitem> | |
| 2226 <literal>posted</literal> - flag, meaning that the event is posted to queue | |
| 2227 </listitem> | |
| 2228 | |
| 2229 <listitem> | |
| 2230 <literal>queue</literal> - queue node for posting the event to a queue | |
| 2231 </listitem> | |
| 2232 | |
| 2233 </list> | |
| 2234 </para> | |
| 2235 | |
| 2236 </section> | |
| 2237 | |
| 2238 | |
| 2239 <section name="I/O events" id="i_o_events"> | |
| 2240 | |
| 2241 <para> | |
| 2242 Each connection, received with the | |
| 2243 <literal>ngx_get_connection()</literal> call, has two events attached to it: | |
| 2244 <literal>c->read</literal> and <literal>c->write</literal>. | |
| 2245 These events are used to receive notifications about the socket being ready for | |
| 2246 reading or writing. | |
| 2247 All such events operate in Edge-Triggered mode, meaning that they only trigger | |
| 2248 notifications when the state of the socket changes. | |
| 2249 For example, doing a partial read on a socket will not make nginx deliver a | |
| 2250 repeated read notification until more data arrive in the socket. | |
| 2251 Even when the underlying I/O notification mechanism is essentially | |
| 2252 Level-Triggered (poll, select etc), nginx will turn the notifications into | |
| 2253 Edge-Triggered. | |
| 2254 To make nginx event notifications consistent across all notifications systems | |
| 2255 on different platforms, it's required, that the functions | |
| 2256 <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
|
2257 <literal>ngx_handle_write_event(wev, lowat)</literal> are called after handling |
| 1899 | 2258 an I/O socket notification or calling any I/O functions on that socket. |
| 2259 Normally, these functions are called once in the end of each read or write | |
| 2260 event handler. | |
| 2261 </para> | |
| 2262 | |
| 2263 </section> | |
| 2264 | |
| 2265 | |
| 2266 <section name="Timer events" id="timer_events"> | |
| 2267 | |
| 2268 <para> | |
| 2269 An event can be set to notify a timeout expiration. | |
| 2270 The function <literal>ngx_add_timer(ev, timer)</literal> sets a timeout for an | |
| 2271 event, <literal>ngx_del_timer(ev)</literal> deletes a previously set timeout. | |
| 2272 Timeouts currently set for all existing events, are kept in a global timeout | |
| 2273 Red-Black tree <literal>ngx_event_timer_rbtree</literal>. | |
| 2274 The key in that tree has the type <literal>ngx_msec_t</literal> and is the time | |
| 2275 in milliseconds since the beginning of January 1, 1970 (modulus | |
| 2276 <literal>ngx_msec_t</literal> max value) at which the event should expire. | |
| 2277 The tree structure provides fast inserting and deleting operations, as well as | |
| 2278 accessing the nearest timeouts. | |
| 2279 The latter is used by nginx to find out for how long to wait for I/O events | |
| 2280 and for expiring timeout events afterwards. | |
| 2281 </para> | |
| 2282 | |
| 2283 </section> | |
| 2284 | |
| 2285 | |
| 2286 <section name="Posted events" id="posted_events"> | |
| 2287 | |
| 2288 <para> | |
| 2289 An event can be posted which means that its handler will be called at some | |
| 2290 point later within the current event loop iteration. | |
| 2291 Posting events is a good practice for simplifying code and escaping stack | |
| 2292 overflows. | |
| 2293 Posted events are held in a post queue. | |
| 2294 The macro <literal>ngx_post_event(ev, q)</literal> posts the event | |
| 2295 <literal>ev</literal> to the post queue <literal>q</literal>. | |
| 2296 Macro <literal>ngx_delete_posted_event(ev)</literal> deletes the event | |
| 2297 <literal>ev</literal> from whatever queue it's currently posted. | |
| 2298 Normally, events are posted to the <literal>ngx_posted_events</literal> queue. | |
| 2299 This queue is processed late in the event loop - after all I/O and timer | |
| 2300 events are already handled. | |
| 2301 The function <literal>ngx_event_process_posted()</literal> is called to process | |
| 2302 an event queue. | |
| 2303 This function calls event handlers until the queue is not empty. This means | |
| 2304 that a posted event handler can post more events to be processed within the | |
| 2305 current event loop iteration. | |
| 2306 </para> | |
| 2307 | |
| 2308 <para> | |
| 2309 Example: | |
| 2310 </para> | |
| 2311 | |
| 2312 | |
| 2313 <programlisting> | |
| 2314 void | |
| 2315 ngx_my_connection_read(ngx_connection_t *c) | |
| 2316 { | |
| 2317 ngx_event_t *rev; | |
| 2318 | |
| 2319 rev = c->read; | |
| 2320 | |
| 2321 ngx_add_timer(rev, 1000); | |
| 2322 | |
| 2323 rev->handler = ngx_my_read_handler; | |
| 2324 | |
| 2325 ngx_my_read(rev); | |
| 2326 } | |
| 2327 | |
| 2328 | |
| 2329 void | |
| 2330 ngx_my_read_handler(ngx_event_t *rev) | |
| 2331 { | |
| 2332 ssize_t n; | |
| 2333 ngx_connection_t *c; | |
| 2334 u_char buf[256]; | |
| 2335 | |
| 2336 if (rev->timedout) { /* timeout expired */ } | |
| 2337 | |
| 2338 c = rev->data; | |
| 2339 | |
| 2340 while (rev->ready) { | |
| 2341 n = c->recv(c, buf, sizeof(buf)); | |
| 2342 | |
| 2343 if (n == NGX_AGAIN) { | |
| 2344 break; | |
| 2345 } | |
| 2346 | |
| 2347 if (n == NGX_ERROR) { /* error */ } | |
| 2348 | |
| 2349 /* process buf */ | |
| 2350 } | |
| 2351 | |
| 2352 if (ngx_handle_read_event(rev, 0) != NGX_OK) { /* error */ } | |
| 2353 } | |
| 2354 </programlisting> | |
| 2355 | |
| 2356 </section> | |
| 2357 | |
| 2358 | |
| 2359 <section name="Event loop" id="event_loop"> | |
| 2360 | |
| 2361 <para> | |
| 2362 All nginx processes which do I/O, have an event loop. | |
| 2363 The only type of process which does not have I/O, is nginx master process which | |
| 2364 spends most of its time in <literal>sigsuspend()</literal> call waiting for | |
| 2365 signals to arrive. | |
| 2366 Event loop is implemented in <literal>ngx_process_events_and_timers()</literal> | |
| 2367 function. | |
| 2368 This function is called repeatedly until the process exits. | |
| 2369 It has the following stages: | |
| 2370 </para> | |
| 2371 | |
| 2372 <para> | |
| 2373 <list type="bullet"> | |
| 2374 | |
| 2375 <listitem> | |
| 2376 find nearest timeout by calling <literal>ngx_event_find_timer()</literal>. | |
| 2377 This function finds the leftmost timer tree node and returns the number of | |
| 2378 milliseconds until that node expires | |
| 2379 </listitem> | |
| 2380 | |
| 2381 <listitem> | |
| 2382 process I/O events by calling a handler, specific to event notification | |
| 2383 mechanism, chosen by nginx configuration. | |
| 2384 This handler waits for at least one I/O event to happen, but no longer, than | |
| 2385 the nearest timeout. | |
| 2386 For each read or write event which has happened, the <literal>ready</literal> | |
| 2387 flag is set and its handler is called. | |
| 2388 For Linux, normally, the <literal>ngx_epoll_process_events()</literal> handler | |
| 2389 is used which calls <literal>epoll_wait()</literal> to wait for I/O events | |
| 2390 </listitem> | |
| 2391 | |
| 2392 <listitem> | |
| 2393 expire timers by calling <literal>ngx_event_expire_timers()</literal>. | |
| 2394 The timer tree is iterated from the leftmost element to the right until a not | |
| 2395 yet expired timeout is found. | |
| 2396 For each expired node the <literal>timedout</literal> event flag is set, | |
| 2397 <literal>timer_set</literal> flag is reset, and the event handler is called | |
| 2398 </listitem> | |
| 2399 | |
| 2400 <listitem> | |
| 2401 process posted events by calling <literal>ngx_event_process_posted()</literal>. | |
| 2402 The function repeatedly removes the first element from the posted events | |
| 2403 queue and calls its handler until the queue gets empty | |
| 2404 </listitem> | |
| 2405 | |
| 2406 </list> | |
| 2407 </para> | |
| 2408 | |
| 2409 <para> | |
| 2410 All nginx processes handle signals as well. | |
| 2411 Signal handlers only set global variables which are checked after the | |
| 2412 <literal>ngx_process_events_and_timers()</literal> call. | |
| 2413 </para> | |
| 2414 | |
| 2415 </section> | |
| 2416 | |
| 2417 | |
| 2418 </section> | |
| 2419 | |
| 2420 | |
| 2421 <section name="Processes" id="processes"> | |
| 2422 | |
| 2423 <para> | |
| 2424 There are several types of processes in nginx. | |
| 2425 The type of current process is kept in the <literal>ngx_process</literal> | |
| 2426 global variable: | |
| 2427 </para> | |
| 2428 | |
| 2429 <list type="bullet"> | |
| 2430 | |
| 2431 <listitem> | |
| 2432 | |
| 2433 <para> | |
| 2434 <literal>NGX_PROCESS_MASTER</literal> - the master process runs the | |
| 2435 <literal>ngx_master_process_cycle()</literal> function. | |
| 2436 Master process does not have any I/O and responds only to signals. | |
| 2437 It reads configuration, creates cycles, starts and controls child processes | |
| 2438 </para> | |
| 2439 | |
| 2440 | |
| 2441 </listitem> | |
| 2442 | |
| 2443 <listitem> | |
| 2444 | |
| 2445 <para> | |
| 2446 <literal>NGX_PROCESS_WORKER</literal> - the worker process runs the | |
| 2447 <literal>ngx_worker_process_cycle()</literal> function. | |
| 2448 Worker processes are started by master and handle client connections. | |
| 2449 They also respond to signals and channel commands, sent from master | |
| 2450 </para> | |
| 2451 | |
| 2452 | |
| 2453 </listitem> | |
| 2454 | |
| 2455 <listitem> | |
| 2456 | |
| 2457 <para> | |
| 2458 <literal>NGX_PROCESS_SINGLE</literal> - single process is the only type | |
| 2459 of processes which exist in the <literal>master_process off</literal> mode. | |
| 2460 The cycle function for this process is | |
| 2461 <literal>ngx_single_process_cycle()</literal>. | |
| 2462 This process creates cycles and handles client connections | |
| 2463 </para> | |
| 2464 | |
| 2465 | |
| 2466 </listitem> | |
| 2467 | |
| 2468 <listitem> | |
| 2469 | |
| 2470 <para> | |
| 2471 <literal>NGX_PROCESS_HELPER</literal> - currently, there are two types of | |
| 2472 helper processes: cache manager and cache loader. | |
| 2473 Both of them share the same cycle function | |
| 2474 <literal>ngx_cache_manager_process_cycle()</literal>. | |
| 2475 </para> | |
| 2476 | |
| 2477 | |
| 2478 </listitem> | |
| 2479 | |
| 2480 </list> | |
| 2481 | |
| 2482 <para> | |
| 2483 All nginx processes handle the following signals: | |
| 2484 </para> | |
| 2485 | |
| 2486 <list type="bullet"> | |
| 2487 | |
| 2488 <listitem> | |
| 2489 | |
| 2490 <para> | |
| 2491 <literal>NGX_SHUTDOWN_SIGNAL</literal> (<literal>SIGQUIT</literal>) - graceful | |
| 2492 shutdown. | |
| 2493 Upon receiving this signal master process sends shutdown signal to all child | |
| 2494 processes. | |
| 2495 When no child processes are left, master destroys cycle pool and exits. | |
| 2496 A worker process which received this signal, closes all listening sockets and | |
| 2497 waits until timeout tree becomes empty, then destroys cycle pool and exits. | |
| 2498 A cache manager process exits right after receiving this signal. | |
| 2499 The variable <literal>ngx_quit</literal> is set to one after receiving this | |
| 2500 signal and immediately reset after being processed. | |
| 2501 The variable <literal>ngx_exiting</literal> is set to one when worker process | |
| 2502 is in shutdown state | |
| 2503 </para> | |
| 2504 | |
| 2505 | |
| 2506 </listitem> | |
| 2507 | |
| 2508 <listitem> | |
| 2509 | |
| 2510 <para> | |
| 2511 <literal>NGX_TERMINATE_SIGNAL</literal> (<literal>SIGTERM</literal>) - | |
| 2512 terminate. | |
| 2513 Upon receiving this signal master process sends terminate signal to all child | |
| 2514 processes. | |
| 2515 If child processes do not exit in 1 second, they are killed with the | |
| 2516 <literal>SIGKILL</literal> signal. | |
| 2517 When no child processes are left, master process destroys cycle pool and exits. | |
| 2518 A worker or cache manager process which received this signal destroys cycle | |
| 2519 pool and exits. | |
| 2520 The variable <literal>ngx_terminate</literal> is set to one after receiving | |
| 2521 this signal | |
| 2522 </para> | |
| 2523 | |
| 2524 | |
| 2525 </listitem> | |
| 2526 | |
| 2527 <listitem> | |
| 2528 | |
| 2529 <para> | |
| 2530 <literal>NGX_NOACCEPT_SIGNAL</literal> (<literal>SIGWINCH</literal>) | |
| 2531 - gracefully shut down worker processes | |
| 2532 </para> | |
| 2533 | |
| 2534 | |
| 2535 </listitem> | |
| 2536 | |
| 2537 <listitem> | |
| 2538 | |
| 2539 <para> | |
| 2540 <literal>NGX_RECONFIGURE_SIGNAL</literal> (<literal>SIGHUP</literal>) - | |
| 2541 reconfigure. | |
| 2542 Upon receiving this signal master process creates a new cycle from | |
| 2543 configuration file. | |
| 2544 If the new cycle was created successfully, the old cycle is deleted and new | |
| 2545 child processes are started. | |
| 2546 Meanwhile, the old processes receive the shutdown signal. | |
| 2547 In single-process mode, nginx creates a new cycle as well, but keeps the old | |
| 2548 one until all clients, tied to the old cycle, are gone. | |
| 2549 Worker and helper processes ignore this signal | |
| 2550 </para> | |
| 2551 | |
| 2552 | |
| 2553 </listitem> | |
| 2554 | |
| 2555 <listitem> | |
| 2556 | |
| 2557 <para> | |
| 2558 <literal>NGX_REOPEN_SIGNAL</literal> (<literal>SIGUSR1</literal>) - reopen | |
| 2559 files. | |
| 2560 Master process passes this signal to workers. | |
| 2561 Worker processes reopen all <literal>open_files</literal> from the cycle | |
| 2562 </para> | |
| 2563 | |
| 2564 | |
| 2565 </listitem> | |
| 2566 | |
| 2567 <listitem> | |
| 2568 | |
| 2569 <para> | |
| 2570 <literal>NGX_CHANGEBIN_SIGNAL</literal> (<literal>SIGUSR2</literal>) - change | |
| 2571 nginx binary. | |
| 2572 Master process starts a new nginx binary and passes there a list of all listen | |
| 2573 sockets. | |
| 2574 The list is passed in the environment variable <literal>"NGINX"</literal> in | |
| 2575 text format, where descriptor numbers separated with semicolons. | |
| 2576 A new nginx instance reads that variable and adds the sockets to its init | |
| 2577 cycle. | |
| 2578 Other processes ignore this signal | |
| 2579 </para> | |
| 2580 | |
| 2581 | |
| 2582 </listitem> | |
| 2583 | |
| 2584 </list> | |
| 2585 | |
| 2586 <para> | |
| 2587 While all nginx worker processes are able to receive and properly handle POSIX | |
| 2588 signals, master process normally does not pass any signals to workers and | |
| 2589 helpers with the standard <literal>kill()</literal> syscall. | |
| 2590 Instead, nginx uses inter-process channels which allow sending messages between | |
| 2591 all nginx processes. | |
| 2592 Currently, however, messages are only sent from master to its children. | |
| 2593 Those messages carry the same signals. | |
| 2594 The channels are socketpairs with their ends in different processes. | |
| 2595 </para> | |
| 2596 | |
| 2597 <para> | |
| 2598 When running nginx binary, several values can be specified next to | |
| 2599 <literal>-s</literal> parameter. | |
| 2600 Those values are <literal>stop</literal>, <literal>quit</literal>, | |
| 2601 <literal>reopen</literal>, <literal>reload</literal>. | |
| 2602 They are converted to signals <literal>NGX_TERMINATE_SIGNAL</literal>, | |
| 2603 <literal>NGX_SHUTDOWN_SIGNAL</literal>, <literal>NGX_REOPEN_SIGNAL</literal> | |
| 2604 and <literal>NGX_RECONFIGURE_SIGNAL</literal> and sent to the nginx master | |
| 2605 process, whose pid is read from nginx pid file. | |
| 2606 </para> | |
| 2607 | |
| 2608 </section> | |
| 2609 | |
| 2610 </article> |