Mercurial > hg > nginx-site
comparison xml/en/docs/http/server_names.xml @ 0:61e04fc01027
Initial import of the nginx.org website.
author | Ruslan Ermilov <ru@nginx.com> |
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date | Thu, 11 Aug 2011 12:19:13 +0000 |
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children | 9d544687d02c |
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1 <!DOCTYPE digest SYSTEM "../../../../dtd/article.dtd"> | |
2 | |
3 <article title="Server names" | |
4 link="/en/docs/http/server_names.html" | |
5 lang="en" | |
6 author="Igor Sysoev" | |
7 editor="Brian Mercer"> | |
8 | |
9 | |
10 <section> | |
11 | |
12 <para> | |
13 Server names are defined using the <dirname>server_name</dirname> directive | |
14 and determine which server block is used for a given request. | |
15 See also “<a href="/en/docs/http/request_processing.xml" />”. | |
16 They may be defined using exact names, wildcard names, or regular expressions: | |
17 | |
18 <programlisting> | |
19 server { | |
20 listen 80; | |
21 server_name nginx.org www.nginx.org; | |
22 ... | |
23 } | |
24 | |
25 server { | |
26 listen 80; | |
27 server_name *.nginx.org; | |
28 ... | |
29 } | |
30 | |
31 server { | |
32 listen 80; | |
33 server_name mail.*; | |
34 ... | |
35 } | |
36 | |
37 server { | |
38 listen 80; | |
39 server_name ~^(?<user>.+)\.nginx\.net$; | |
40 ... | |
41 } | |
42 </programlisting> | |
43 | |
44 The names are tested in the following order: | |
45 | |
46 <orderedlist> | |
47 | |
48 <item> | |
49 exact names; | |
50 </item> | |
51 | |
52 <item> | |
53 wildcard names starting with an asterisk: <url>*.nginx.org</url>; | |
54 </item> | |
55 | |
56 <item> | |
57 wildcard names ending with an asterisk: <url>mail.*</url>; | |
58 </item> | |
59 | |
60 <item> | |
61 and regular expressions in the order listed in the configuration file. | |
62 </item> | |
63 | |
64 </orderedlist> | |
65 The first match stops the search. | |
66 </para> | |
67 | |
68 </section> | |
69 | |
70 | |
71 <section name="wildcard_names" | |
72 title="Wildcard names"> | |
73 | |
74 <para> | |
75 A wildcard name may contain an asterisk only on the name's start or end, | |
76 and only on a dot border. The names <dirname>www.*.nginx.org</dirname> | |
77 and <dirname>w*.nginx.org</dirname> are invalid. | |
78 However, these names can be specified using regular expressions, | |
79 for example, <dirname>~^www\..+\.nginx\.org$</dirname> and | |
80 <dirname>~^w.*\.nginx\.org$</dirname>. | |
81 An asterisk can match several name parts. | |
82 The name <dirname>*.nginx.org</dirname> matches not only | |
83 <url>www.nginx.org</url> but <url>www.sub.nginx.org</url> as well. | |
84 </para> | |
85 | |
86 <para> | |
87 A special wildcard in the form <dirname>.nginx.org</dirname> can be used | |
88 to match both the exact name <dirname>nginx.org</dirname> | |
89 and the wildcard name <dirname>*.nginx.org</dirname>. | |
90 </para> | |
91 | |
92 </section> | |
93 | |
94 | |
95 <section name="regex_names" | |
96 title="Regular expressions names"> | |
97 | |
98 <para> | |
99 The regular expressions used by nginx are compatible with those used | |
100 by the Perl programming language (PCRE). | |
101 To use a regular expression, the server name must start with the tilde | |
102 character: | |
103 | |
104 <programlisting> | |
105 server_name ~^www\d+\.nginx\.net$; | |
106 </programlisting> | |
107 | |
108 otherwise it will be treated as an exact name, or if the expression contains | |
109 an asterisk, as a wildcard name (and most likely as an invalid one). | |
110 Do not forget to set “^” and “$” anchors. | |
111 They are not required syntactically, but logically. | |
112 Also note that domain name dots should be escaped with a backslash. | |
113 A regular expression containing the characters “{” | |
114 and “}” should be quoted: | |
115 | |
116 <programlisting> | |
117 server_name "~^(?<name>\w\d<b>{</b>1,3<b>}</b>+)\.nginx\.net$"; | |
118 </programlisting> | |
119 | |
120 otherwise nginx will fail to start and display the error message: | |
121 | |
122 <programlisting> | |
123 directive "server_name" is not terminated by ";" in ... | |
124 </programlisting> | |
125 | |
126 A named regular expression capture can be used later as a variable: | |
127 | |
128 <programlisting> | |
129 server { | |
130 server_name ~^(www\.)?(<b>?<domain></b>.+)$; | |
131 | |
132 location / { | |
133 root /sites/<b>$domain</b>; | |
134 } | |
135 } | |
136 </programlisting> | |
137 | |
138 The PCRE library supports named captures using the following syntax: | |
139 | |
140 <table note="yes"> | |
141 | |
142 <tr> | |
143 <td><code>?<<i>name</i>></code></td> | |
144 <td>Perl 5.10 compatible syntax, supported since PCRE-7.0</td> | |
145 </tr> | |
146 | |
147 <tr> | |
148 <td><code>?'<i>name</i>'</code></td> | |
149 <td>Perl 5.10 compatible syntax, supported since PCRE-7.0</td> | |
150 </tr> | |
151 | |
152 <tr> | |
153 <td><code>?P<<i>name</i>></code></td> | |
154 <td>Python compatible syntax, supported since PCRE-4.0</td> | |
155 </tr> | |
156 | |
157 </table> | |
158 | |
159 If nginx fails to start and displays the error message: | |
160 | |
161 <programlisting> | |
162 pcre_compile() failed: unrecognized character after (?< in ... | |
163 </programlisting> | |
164 | |
165 this means that the PCRE library is old | |
166 and you should try the syntax <dirname>?P<<i>name</i>></dirname>. | |
167 The captures can also be used in digital form: | |
168 | |
169 <programlisting> | |
170 server { | |
171 server_name ~^(www\.)?(.+)$; | |
172 | |
173 location / { | |
174 root /sites/<b>$2</b>; | |
175 } | |
176 } | |
177 </programlisting> | |
178 | |
179 However, such usage should be limited to simple cases (like the above), | |
180 since the digital references can easily be overwritten. | |
181 </para> | |
182 | |
183 | |
184 </section> | |
185 | |
186 | |
187 <section name="miscellaneous_names" | |
188 title="Miscellaneous names"> | |
189 | |
190 <para> | |
191 If you want to process requests without a “Host” header line | |
192 in a server block which is not the default, you should specify an empty name: | |
193 | |
194 <programlisting> | |
195 server { | |
196 listen 80; | |
197 server_name nginx.org www.nginx.org ""; | |
198 ... | |
199 } | |
200 </programlisting> | |
201 </para> | |
202 | |
203 <para> | |
204 If no <dirname>server_name</dirname> is defined in a server block, | |
205 then nginx uses the empty name as the server name. | |
206 <note> | |
207 nginx versions up to 0.8.48 used the <i>hostname</i> as the server name | |
208 in this case. | |
209 </note> | |
210 </para> | |
211 | |
212 <para> | |
213 If someone makes a request using an IP address instead of a server name, | |
214 the request’s “Host” header line will contain the IP address | |
215 and you can handle the request using the IP address as the server name: | |
216 | |
217 <programlisting> | |
218 server { | |
219 listen 80; | |
220 server_name nginx.org | |
221 www.nginx.org | |
222 "" | |
223 <b>192.168.1.1</b> | |
224 ; | |
225 ... | |
226 } | |
227 </programlisting> | |
228 </para> | |
229 | |
230 <para> | |
231 In catch-all server examples you may see the strange name “_”: | |
232 | |
233 <programlisting> | |
234 server { | |
235 listen 80 default_server; | |
236 server_name _; | |
237 return 444; | |
238 } | |
239 </programlisting> | |
240 | |
241 There is nothing special about this name, it is just one of a myriad | |
242 of invalid domain names which never intersect with any real name. | |
243 You may also use something like “--”, “!@#”, and so on. | |
244 </para> | |
245 | |
246 <para> | |
247 nginx versions up to 0.6.25 supported the special name “*” | |
248 which was erroneously interpreted to be a catch-all name. | |
249 It never functioned as a catch-all or wildcard server name. | |
250 Instead, it supplied the functionality that is now provided | |
251 by the <dirname>server_name_in_redirect</dirname> directive. | |
252 The special name “*” is now deprecated | |
253 and the <dirname>server_name_in_redirect</dirname> directive should be used. | |
254 Note that there is no way to specify the catch-all name or | |
255 the <i>default</i> server using the <dirname>server_name</dirname> directive. | |
256 This is a property of the <dirname>listen</dirname> directive | |
257 and not of the <dirname>server_name</dirname> directive. | |
258 See also “<a href="/en/docs/http/request_processing.xml" />”. | |
259 You can define servers listening on ports *:80 and *:8080, | |
260 and direct that one will be the default server for port *:8080, | |
261 while the other will be the default for port *:80: | |
262 | |
263 <programlisting> | |
264 server { | |
265 listen 80; | |
266 listen 8080 default_server; | |
267 server_name nginx.net; | |
268 ... | |
269 } | |
270 | |
271 server { | |
272 listen 80 default_server; | |
273 listen 8080; | |
274 server_name nginx.org; | |
275 ... | |
276 } | |
277 </programlisting> | |
278 </para> | |
279 | |
280 | |
281 </section> | |
282 | |
283 | |
284 <section name="optimization" | |
285 title="Optimization"> | |
286 | |
287 <para> | |
288 Exact names and wildcard names are stored in hashes. | |
289 The hashes are bound to the listen ports and every listen port | |
290 may have up to three hashes: an exact names hash, a wildcard names hash | |
291 starting with an asterisk, and a wildcard names hash ending with an asterisk. | |
292 The sizes of the hashes are optimized at the configuration phase so that | |
293 a name can be found with the fewest CPU cache misses. | |
294 The exact names hash is searched first. | |
295 If a name is not found using the exact name hash, then the wildcard names hash | |
296 starting with an asterisk is searched. | |
297 If the name is not found there, the wildcard names hash | |
298 ending with an asterisk is searched. | |
299 Searching wildcard names hashes is slower than searching exact name hash | |
300 because names are searched by domain parts. | |
301 Note that the special wildcard form <dirname>.nginx.org</dirname> | |
302 is stored in a wildcard names hash and not in an exact names hash. | |
303 Regular expressions are tested sequentially | |
304 and therefore are the slowest method and are non-scalable. | |
305 </para> | |
306 | |
307 <para> | |
308 For these reasons, it is better to use exact names where possible. | |
309 For example, if the most frequently requested names of a server | |
310 are <url>nginx.org</url> and <url>www.nginx.org</url>, | |
311 it is more efficient to define them explicitly: | |
312 | |
313 <programlisting> | |
314 server { | |
315 listen 80; | |
316 server_name nginx.org www.nginx.org *.nginx.org; | |
317 ... | |
318 } | |
319 </programlisting> | |
320 | |
321 than to use the simplified form: | |
322 | |
323 <programlisting> | |
324 server { | |
325 listen 80; | |
326 server_name .nginx.org; | |
327 ... | |
328 } | |
329 </programlisting> | |
330 </para> | |
331 | |
332 <para> | |
333 If you have defined a large number of server names, | |
334 or defined unusually long server names, you may need to tune | |
335 the <dirname>server_names_hash_max_size</dirname> | |
336 and <dirname>server_names_hash_bucket_size</dirname> directives | |
337 at the <i>http</i> level. | |
338 The default value of the <dirname>server_names_hash_bucket_size</dirname> | |
339 may be equal to 32, or 64, or another value, | |
340 depending on your CPU cache line size. | |
341 If the default value is 32 and you define | |
342 “too.long.server.name.nginx.org” as a server name, | |
343 then nginx will fail to start and display the error message: | |
344 | |
345 <programlisting> | |
346 could not build the server_names_hash, | |
347 you should increase server_names_hash_bucket_size: 32 | |
348 </programlisting> | |
349 | |
350 In this case, you should set the directive value to the next power of 2: | |
351 | |
352 <programlisting> | |
353 http { | |
354 server_names_hash_bucket_size 64; | |
355 ... | |
356 </programlisting> | |
357 | |
358 If you have defined a large number of server names, | |
359 you will get another error message: | |
360 | |
361 <programlisting> | |
362 could not build the server_names_hash, | |
363 you should increase either server_names_hash_max_size: 512 | |
364 or server_names_hash_bucket_size: 32 | |
365 </programlisting> | |
366 | |
367 You should first try to set <dirname>server_names_hash_max_size</dirname> | |
368 to a number close to the number of server names. | |
369 Only if this does not help, | |
370 or if nginx’s start time is unacceptably long, | |
371 should you try to increase <dirname>server_names_hash_bucket_size</dirname>. | |
372 </para> | |
373 | |
374 <para> | |
375 If a server is the only server for a listen port, then nginx will not test | |
376 server names at all (and will not build the hashes for the listen port). | |
377 However, there is one exception. | |
378 If a <dirname>server_name</dirname> is a regular expression with captures, | |
379 then nginx has to execute the expression to get the captures. | |
380 </para> | |
381 | |
382 </section> | |
383 | |
384 | |
385 <section name="compatibility" | |
386 title="Compatibility"> | |
387 | |
388 <para> | |
389 <list> | |
390 | |
391 <item> | |
392 A default server name value is an empty name “” since 0.8.48. | |
393 </item> | |
394 | |
395 <item> | |
396 Named regular expression server name captures have been supported since 0.8.25. | |
397 </item> | |
398 | |
399 <item> | |
400 Regular expression server name captures have been supported since 0.7.40. | |
401 </item> | |
402 | |
403 <item> | |
404 An empty server name “” has been supported since 0.7.12. | |
405 </item> | |
406 | |
407 <item> | |
408 A wildcard server name or regular expression has been supported for use | |
409 as the first server name since 0.6.25. | |
410 </item> | |
411 | |
412 <item> | |
413 Regular expression server names have been supported since 0.6.7. | |
414 </item> | |
415 | |
416 <item> | |
417 Wildcard form <url>nginx.*</url> has been supported since 0.6.0. | |
418 </item> | |
419 | |
420 <item> | |
421 The special form <url>.nginx.org</url> has been supported since 0.3.18. | |
422 </item> | |
423 | |
424 <item> | |
425 Wildcard form <url>*.nginx.org</url> has been supported since 0.1.13. | |
426 </item> | |
427 | |
428 </list> | |
429 </para> | |
430 | |
431 </section> | |
432 | |
433 </article> |