nginx rewrite执行顺序（二）

例题 1

配置：

error_log  logs/error.log info;

server {

        listen       9090;

        server_name  localhost;

        root html;

        rewrite_log on;

        rewrite "^/aaa\.html$"  /bbb.html;

        location  /ccc.html {

            rewrite "^/ccc\.html$"  /eee.html;

        }

        location  /bbb.html {

            rewrite "^/bbb\.html$" /ccc.html;

            rewrite "^/ccc\.html$" /ddd.html;

        }  

}   

结果：

[root@web108 ~]# curl http://localhost:9090/aaa.html

ddd html file

[root@web108 ~]#

日志：

2011/08/08 10:05:41 [notice] 31592#0: *90 "^/aaa\.html$" matches "/aaa.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:05:41 [notice] 31592#0: *90 rewritten data: "/bbb.html" , args: "", client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:05:41 [notice] 31592#0: *90 "^/bbb\.html$" matches "/bbb.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:05:41 [notice] 31592#0: *90 rewritten data: "/ccc.html" , args: "", client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:05:41 [notice] 31592#0: *90 "^/ccc\.html$" matches "/ccc.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:05:41 [notice] 31592#0: *90 rewritten data: "/ddd.html" , args: "", client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:05:41 [notice] 31592#0: *90 "^/aaa\.html$" does not match "/ddd.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:05:41 [info] 31592#0: *90 client 127.0.0.1 closed keepalive connection

解释：

GET /aaa.html 请求，首先执行 server 级的 rewrite 指令，被重写为 /bbb.html ，然后匹配到 location /bbb.html {} ，接着执行 location 级的 rewrite 指令，先重写为 /ccc.html ，再重写为 /ddd.html ；由于 URI 被 location 级的 rewrite 指令重写了，因此需要重新进行 location 的匹配，相当于重写后的 URI 被当做一个新的请求，会重新执行 server 级的 rewrite ，然后重新匹配 location ，日志“ 2011/08/08 10:05:41 [notice] 31592#0: *90 "^/aaa\.html$" does not match "/ddd.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090" ”体现了重新匹配 location 的流程。

例题 2

配置：

error_log  logs/error.log info;

server {

        listen       9090;

        server_name  localhost;

        root html;

        rewrite_log on;

        rewrite "^/aaa\.html$"  /bbb.html;

                   rewrite "^/ccc\.html$"  /ddd.html;

        location  /bbb.html {

            rewrite "^/bbb\.html$" /ccc.html;

        }  

                   location  /ddd.html {

             rewrite "^/ddd\.html$" /eee.html;

        }

}   

结果：

[root@web108 ~]# curl http://localhost:9090/aaa.html

eee html file

[root@web108 ~]#

日志：

2011/08/08 10:21:00 [notice] 2218#0: *91 "^/aaa\.html$" matches "/aaa.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 rewritten data: "/bbb.html" , args: "", client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 "^/ccc\.html$" does not match "/bbb.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 "^/bbb\.html$" matches "/bbb.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 rewritten data: "/ccc.html" , args: "", client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 "^/aaa\.html$" does not match "/ccc.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 "^/ccc\.html$" matches "/ccc.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 rewritten data: "/ddd.html" , args: "", client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 "^/ddd\.html$" matches "/ddd.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 rewritten data: "/eee.html" , args: "", client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 "^/aaa\.html$" does not match "/eee.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [notice] 2218#0: *91 "^/ccc\.html$" does not match "/eee.html" , client: 127.0.0.1, server: localhost, request: "GET /aaa.html HTTP/1.1", host: "localhost:9090"

2011/08/08 10:21:00 [info] 2218#0: *91 client 127.0.0.1 closed keepalive connection

解释：

第一次迭代 location 匹配

GET /aaa.html ，首先执行 server 级的重写，“ rewrite "^/aaa\.html$"  /bbb.html ”把 /aaa.html 重写为 /bbb.html ，但 /bbb.html 没匹配上“ rewrite "^/ccc\.html$"  /ddd.html ”，最终保留 /bbb.html ；接着，匹配 location /bbb.html {} ，执行 location 级的 rewrite 指令，把 /bbb.html 重写为 /ccc.html ，由于 URI 被 location 级 rewrite 重写，因此需要重新迭代 location 匹配。

第二次迭代 location 匹配

对于第一次迭代结果 /ccc.html ，首先依然是执行 server 级的 rewrite 指令，“ rewrite "^/aaa\.html$"  /bbb.html; ”跟 /ccc.html 不匹配，但“ rewrite "^/ccc\.html$"  /ddd.html; ”把 /ccc.html 重写为 /ddd.html ； server 级 rewrite 执行完后，接着 location 匹配， /ddd.html 匹配到 location /ddd.html {} ，执行 location 级的 rewrite 指令，把 /ddd.html 重写为 /eee.html 。同样由于 URI 被 location 级的 rewrite 指令重写，于是需要重新迭代 location 匹配。

第三次迭代 location 匹配

对于第二次迭代结果 /eee.html ，首先依然执行 server 级的 rewrite 指令，“ rewrite "^/aaa\.html$"  /bbb.html; ”和“ rewrite "^/ccc\.html$"  /ddd.html; ”，只不过它们都没匹配上 /eee.html ，接着 /eee.html 进行 location 匹配，也没有，最终结果是 /eee.html ，返回“ eee html file ”页面。

最后说明下，如果把上述配置修改成server级rewrite和location的编辑顺序调整：

server {
        listen       9090;
        server_name  localhost;
        root html;
        rewrite_log on;

               
        location  /bbb.html {
            rewrite "^/bbb\.html$" /ccc.html;
        }   
        location  /ddd.html {
            rewrite "^/ddd\.html$" /eee.html;
        }

        rewrite "^/aaa\.html$"  /bbb.html;
        rewrite "^/ccc\.html$"  /ddd.html;
}

结果是不会受影响的，也就是说location匹配迭代总是先执行server级rewrite，再进行location匹配，再执行location级的rewrite，如果URI因location级rewrite指令重写，则需要进行下一次迭代。但总的迭代次数不超过10次，否则nginx报500错误。

简单伪代码描述下rewrite执行过程：

boolean match_finish = false;
int match_count = 0;
while(!match_finish && match_count < 10) {
        match_count ++;
    （1）按编辑顺序执行server级的rewrite指令；
    （2）按重写后的URI匹配location；
    （3）
        String uri_before_location = uri;
        按编辑顺序执行location级的rewrite指令；
        String uri_after_location = rewrite(uri);
        if(uri_before_location != uri_after_location) {
            match_finish = false;            
        } else {
            match_finish = true;
        }
        if(location rewrite has last flag) {
            continue;//表示不执行后面的rewrite，直接进入下一次迭代
        }
        if(location rewrite has break flag) {
            break;//表示不执行后面的rewrite，并退出循环迭代
        }
}
if(match_count <= 10) {
    return HTTP_200;
} else {
    return HTTP_500;
}