caching - Nginx:限速和缓存按什么顺序执行？

Question

我想使用 nginx 进行速率限制和缓存。

nginx 以什么顺序应用它们？换句话说，它是仅限制对上游服务器的请求还是所有请求(包括缓存 HIT)？

如何更改此顺序？我认为它可以通过两个 server 来改变上下文。因此，例如，在一个 server执行缓存。它有第二个 server上下文作为上游。第二个限制对“真实”上游的请求。但这可能不是最有效的方法......

Answer 1

请求处理
Nginx 请求处理是通过许多不同的阶段完成的，每个阶段都有一个或多个处理程序。模块可以注册以在特定阶段运行。
http://www.nginxguts.com/phases/
http://nginx.org/en/docs/dev/development_guide.html#http_phases
速率限制ngx_http_limit_req_module 应用了速率限制。在 预访问阶段 .来自 ngx_http_limit_req_module.c :

h = ngx_array_push(&cmcf->phases[NGX_HTTP_PREACCESS_PHASE].handlers);

缓存
缓存是稍后完成的，我认为是在内容阶段。
通过查看代码或文档，我无法完全弄清楚这一点。但我能够通过调试构建来证明这一点。我的配置有速率限制每秒 1 个请求，并启用缓存。请参阅我的日志中的以下摘录。
缓存请求

...
2020/08/01 11:11:07 [debug] 17498#0: *7 http header done
2020/08/01 11:11:07 [debug] 17498#0: *7 rewrite phase: 0
2020/08/01 11:11:07 [debug] 17498#0: *7 test location: "/"
2020/08/01 11:11:07 [debug] 17498#0: *7 using configuration "=/"
2020/08/01 11:11:07 [debug] 17498#0: *7 http cl:-1 max:1048576
2020/08/01 11:11:07 [debug] 17498#0: *7 rewrite phase: 2
2020/08/01 11:11:07 [debug] 17498#0: *7 post rewrite phase: 3
2020/08/01 11:11:07 [debug] 17498#0: *7 generic phase: 4
2020/08/01 11:11:07 [debug] 17498#0: *7 http script var: ....
2020/08/01 11:11:07 [debug] 17498#0: shmtx lock
2020/08/01 11:11:07 [debug] 17498#0: shmtx unlock
2020/08/01 11:11:07 [debug] 17498#0: *7 limit_req[0]: 0 0.000
2020/08/01 11:11:07 [debug] 17498#0: *7 generic phase: 5
2020/08/01 11:11:07 [debug] 17498#0: *7 access phase: 6
2020/08/01 11:11:07 [debug] 17498#0: *7 access phase: 7
2020/08/01 11:11:07 [debug] 17498#0: *7 post access phase: 8
2020/08/01 11:11:07 [debug] 17498#0: *7 generic phase: 9
2020/08/01 11:11:07 [debug] 17498#0: *7 generic phase: 10
2020/08/01 11:11:07 [debug] 17498#0: *7 http init upstream, client timer: 0
2020/08/01 11:11:07 [debug] 17498#0: *7 http cache key: "http://127.0.0.1:9000"
2020/08/01 11:11:07 [debug] 17498#0: *7 http cache key: "/"
2020/08/01 11:11:07 [debug] 17498#0: *7 add cleanup: 00005609F7C51578
2020/08/01 11:11:07 [debug] 17498#0: shmtx lock
2020/08/01 11:11:07 [debug] 17498#0: shmtx unlock
2020/08/01 11:11:07 [debug] 17498#0: *7 http file cache exists: 0 e:1
2020/08/01 11:11:07 [debug] 17498#0: *7 cache file: "/home/poida/src/nginx-1.15.6/objs/cache/157d4d91f488c05ff417723d74d65b36"
2020/08/01 11:11:07 [debug] 17498#0: *7 add cleanup: 00005609F7C46810
2020/08/01 11:11:07 [debug] 17498#0: *7 http file cache fd: 12
2020/08/01 11:11:07 [debug] 17498#0: *7 read: 12, 00005609F7C46890, 519, 0
2020/08/01 11:11:07 [debug] 17498#0: *7 http upstream cache: 0
2020/08/01 11:11:07 [debug] 17498#0: *7 http proxy status 200 "200 OK"
2020/08/01 11:11:07 [debug] 17498#0: *7 http proxy header: "Server: SimpleHTTP/0.6 Python/3.8.5"
2020/08/01 11:11:07 [debug] 17498#0: *7 http proxy header: "Date: Sat, 01 Aug 2020 01:11:03 GMT"
2020/08/01 11:11:07 [debug] 17498#0: *7 http proxy header: "Content-type: text/html; charset=utf-8"
2020/08/01 11:11:07 [debug] 17498#0: *7 http proxy header: "Content-Length: 340"
2020/08/01 11:11:07 [debug] 17498#0: *7 http proxy header done
2020/08/01 11:11:07 [debug] 17498#0: *7 http file cache send: /home/poida/src/nginx-1.15.6/objs/cache/157d4d91f488c05ff417723d74d65b36
2020/08/01 11:11:07 [debug] 17498#0: *7 posix_memalign: 00005609F7C46DC0:4096 @16
2020/08/01 11:11:07 [debug] 17498#0: *7 HTTP/1.1 200 OK
...

限价请求

...
2020/08/01 11:17:04 [debug] 17498#0: *10 http header done
2020/08/01 11:17:04 [debug] 17498#0: *10 rewrite phase: 0
2020/08/01 11:17:04 [debug] 17498#0: *10 test location: "/"
2020/08/01 11:17:04 [debug] 17498#0: *10 using configuration "=/"
2020/08/01 11:17:04 [debug] 17498#0: *10 http cl:-1 max:1048576
2020/08/01 11:17:04 [debug] 17498#0: *10 rewrite phase: 2
2020/08/01 11:17:04 [debug] 17498#0: *10 post rewrite phase: 3
2020/08/01 11:17:04 [debug] 17498#0: *10 generic phase: 4
2020/08/01 11:17:04 [debug] 17498#0: *10 http script var: ....
2020/08/01 11:17:04 [debug] 17498#0: shmtx lock
2020/08/01 11:17:04 [debug] 17498#0: shmtx unlock
2020/08/01 11:17:04 [debug] 17498#0: *10 limit_req[0]: -3 0.707
2020/08/01 11:17:04 [error] 17498#0: *10 limiting requests, excess: 0.707 by zone "mylimit", client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "localhost:8080"
2020/08/01 11:17:04 [debug] 17498#0: *10 http finalize request: 503, "/?" a:1, c:1
2020/08/01 11:17:04 [debug] 17498#0: *10 http special response: 503, "/?"
2020/08/01 11:17:04 [debug] 17498#0: *10 http set discard body
2020/08/01 11:17:04 [debug] 17498#0: *10 HTTP/1.1 503 Service Temporarily Unavailable
...

对于速率受限的请求，处理在服务器尝试生成内容或检查缓存之前停止。
TL;博士;在缓存之前首先应用速率限制。