09 nginx 中 upstream max_conns 配置为 1, 导致的一部分静态资源请求成功, 一部分静态资源请求失败

Posted 2022-12-13 蓝风9

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篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了09 nginx 中 upstream max_conns 配置为 1, 导致的一部分静态资源请求成功, 一部分静态资源请求失败相关的知识，希望对你有一定的参考价值。

前言

呵呵这是之前搭建一个项目的时候出现的问题

主要的情况是一个 nginx, 代理了上游的服务, 设置的 max_conns 为 1, 然后之后 nginx 来请求上游的服务的时候一部分请求成功, 一部分请求失败

这里我们来从源码层面上剖析一下这个问题, 以及 max_conns 的理解

测试用例

nginx 配置文件如下

    # upstream list
    upstream api_server 
#        server localhost:18080 max_conns=1;
        server localhost:63344 max_conns=1;
    

    // 省略部分其他配置 
        location / 
            #root   html;
            #index  index.html index.htm;
            proxy_set_header Host $host;
                proxy_pass http://api_server;

上游的服务的 html, 这里会级联获取依赖的 100 个 js 文件

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>H5DrawImage.html</title>
</head>
<body>

</body>

<script src="./js/js01.js" type="text/javascript"></script>
<script src="./js/js02.js" type="text/javascript"></script>
<script src="./js/js03.js" type="text/javascript"></script>
<script src="./js/js04.js" type="text/javascript"></script>
<script src="./js/js05.js" type="text/javascript"></script>
<script src="./js/js06.js" type="text/javascript"></script>
<script src="./js/js07.js" type="text/javascript"></script>
<script src="./js/js08.js" type="text/javascript"></script>
<script src="./js/js09.js" type="text/javascript"></script>
<script src="./js/js10.js" type="text/javascript"></script>
<script src="./js/js11.js" type="text/javascript"></script>
<script src="./js/js12.js" type="text/javascript"></script>
<script src="./js/js13.js" type="text/javascript"></script>
<script src="./js/js14.js" type="text/javascript"></script>
<script src="./js/js15.js" type="text/javascript"></script>
<script src="./js/js16.js" type="text/javascript"></script>
<script src="./js/js17.js" type="text/javascript"></script>
<script src="./js/js18.js" type="text/javascript"></script>
<script src="./js/js19.js" type="text/javascript"></script>
<script src="./js/js20.js" type="text/javascript"></script>
<script src="./js/js21.js" type="text/javascript"></script>
<script src="./js/js22.js" type="text/javascript"></script>
<script src="./js/js23.js" type="text/javascript"></script>
<script src="./js/js24.js" type="text/javascript"></script>
<script src="./js/js25.js" type="text/javascript"></script>
<script src="./js/js26.js" type="text/javascript"></script>
<script src="./js/js27.js" type="text/javascript"></script>
<script src="./js/js28.js" type="text/javascript"></script>
<script src="./js/js29.js" type="text/javascript"></script>
<script src="./js/js30.js" type="text/javascript"></script>
<script src="./js/js31.js" type="text/javascript"></script>
<script src="./js/js32.js" type="text/javascript"></script>
<script src="./js/js33.js" type="text/javascript"></script>
<script src="./js/js34.js" type="text/javascript"></script>
<script src="./js/js35.js" type="text/javascript"></script>
<script src="./js/js36.js" type="text/javascript"></script>
<script src="./js/js37.js" type="text/javascript"></script>
<script src="./js/js38.js" type="text/javascript"></script>
<script src="./js/js39.js" type="text/javascript"></script>
<script src="./js/js40.js" type="text/javascript"></script>
<script src="./js/js41.js" type="text/javascript"></script>
<script src="./js/js42.js" type="text/javascript"></script>
<script src="./js/js43.js" type="text/javascript"></script>
<script src="./js/js44.js" type="text/javascript"></script>
<script src="./js/js45.js" type="text/javascript"></script>
<script src="./js/js46.js" type="text/javascript"></script>
<script src="./js/js47.js" type="text/javascript"></script>
<script src="./js/js48.js" type="text/javascript"></script>
<script src="./js/js49.js" type="text/javascript"></script>
<script src="./js/js50.js" type="text/javascript"></script>
<script src="./js/js51.js" type="text/javascript"></script>
<script src="./js/js52.js" type="text/javascript"></script>
<script src="./js/js53.js" type="text/javascript"></script>
<script src="./js/js54.js" type="text/javascript"></script>
<script src="./js/js55.js" type="text/javascript"></script>
<script src="./js/js56.js" type="text/javascript"></script>
<script src="./js/js57.js" type="text/javascript"></script>
<script src="./js/js58.js" type="text/javascript"></script>
<script src="./js/js59.js" type="text/javascript"></script>
<script src="./js/js60.js" type="text/javascript"></script>
<script src="./js/js61.js" type="text/javascript"></script>
<script src="./js/js62.js" type="text/javascript"></script>
<script src="./js/js63.js" type="text/javascript"></script>
<script src="./js/js64.js" type="text/javascript"></script>
<script src="./js/js65.js" type="text/javascript"></script>
<script src="./js/js66.js" type="text/javascript"></script>
<script src="./js/js67.js" type="text/javascript"></script>
<script src="./js/js68.js" type="text/javascript"></script>
<script src="./js/js69.js" type="text/javascript"></script>
<script src="./js/js70.js" type="text/javascript"></script>
<script src="./js/js71.js" type="text/javascript"></script>
<script src="./js/js72.js" type="text/javascript"></script>
<script src="./js/js73.js" type="text/javascript"></script>
<script src="./js/js74.js" type="text/javascript"></script>
<script src="./js/js75.js" type="text/javascript"></script>
<script src="./js/js76.js" type="text/javascript"></script>
<script src="./js/js77.js" type="text/javascript"></script>
<script src="./js/js78.js" type="text/javascript"></script>
<script src="./js/js79.js" type="text/javascript"></script>
<script src="./js/js80.js" type="text/javascript"></script>
<script src="./js/js81.js" type="text/javascript"></script>
<script src="./js/js82.js" type="text/javascript"></script>
<script src="./js/js83.js" type="text/javascript"></script>
<script src="./js/js84.js" type="text/javascript"></script>
<script src="./js/js85.js" type="text/javascript"></script>
<script src="./js/js86.js" type="text/javascript"></script>
<script src="./js/js87.js" type="text/javascript"></script>
<script src="./js/js88.js" type="text/javascript"></script>
<script src="./js/js89.js" type="text/javascript"></script>
<script src="./js/js90.js" type="text/javascript"></script>
<script src="./js/js91.js" type="text/javascript"></script>
<script src="./js/js92.js" type="text/javascript"></script>
<script src="./js/js93.js" type="text/javascript"></script>
<script src="./js/js94.js" type="text/javascript"></script>
<script src="./js/js95.js" type="text/javascript"></script>
<script src="./js/js96.js" type="text/javascript"></script>
<script src="./js/js97.js" type="text/javascript"></script>
<script src="./js/js98.js" type="text/javascript"></script>
<script src="./js/js99.js" type="text/javascript"></script>

<script>
</script>

</html>

从浏览器访问该服务如下, 确保服务正常

nginx 代理访问该服务状态如下, 可以看到绝大多数的请求 502 请求失败了

但是依然存在一部分请求, 正常响应

参数 max_conns

以下截图来自于官方文档 Module ngx_http_upstream_module

可以看到其实就是对于 upstream 的一个保护, 做了一个并发量控制

但是我们这里只有一个 worker !

但是我们考虑另外一个问题, 在之前的调试过程中我们能够发现的是 worker process 是只有一个线程, 那么即使是客户端这边发送了一百多个请求过来, 那么这个 worker process 也应该是一个请求一个请求的处理呀? 怎么会出现这种情况 ??

nginx 的请求处理方式

nginx 的请求处理调试可以参考文章 nginx 的一次请求处理调试

是根据事件来处理

也就是接受请求, 和向上游发送代理请求, 接受上游的代理响应这三者不是串行的

那么可能是接受了请求1, 接受了请求2, 处理请求1 处理成功, 接着处理请求2, 因为请求1还没有处理完成, 因此处理请求2 的时候会造成超过 max_conns 的限制, 导致处理失败

正常情况应该是走如下 peers->single 下面的 max_conns 的校验, 然后返回 NGX_BUSY

但是 mac 这里似乎我 api_servers 只配置了一个后台服务, 这里 peers 中却有两个节点?? 呵呵这个多久看一下

然后在上层 NGX_BUSY, 响应给了客户端 502

我们在接受请求的地方, 发送代理请求的地方, 接受上游的代理响应的地方加上日志输出

可以看到的是如下几个特征

1. recv 之后的下一个请求应该就是下一次发送成功的请求

2. recv 之后的下一个 accept 到这个 accept 的 recv 之间所有接受的请求都是 502 处理失败

accept http - /HelloWorld/getMultiResource/GetMultiResource.html HTTP/1.1
send - /HelloWorld/getMultiResource/GetMultiResource.html HTTP/1.1
recv - /HelloWorld/getMultiResource/GetMultiResource.html HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js01.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js02.js HTTP/1.1
accept http - /50x.html
send - /HelloWorld/getMultiResource/js/js01.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js03.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js04.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js05.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js06.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js07.js HTTP/1.1
accept http - /50x.html
recv - /HelloWorld/getMultiResource/js/js01.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js08.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js09.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js10.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js11.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js12.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js13.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js14.js HTTP/1.1
accept http - /50x.html
send - /HelloWorld/getMultiResource/js/js08.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js15.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js16.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js17.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js18.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js19.js HTTP/1.1
accept http - /50x.html
recv - /HelloWorld/getMultiResource/js/js08.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js20.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js21.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js22.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js23.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js24.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js25.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js26.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js27.js HTTP/1.1
accept http - /50x.html
send - /HelloWorld/getMultiResource/js/js20.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js28.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js29.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js30.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js31.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js32.js HTTP/1.1
accept http - /50x.html
recv - /HelloWorld/getMultiResource/js/js20.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js33.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js34.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js35.js HTTP/1.1
accept http - /50x.html
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js36.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js37.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js38.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js39.js HTTP/1.1
accept http - /50x.html
send - /HelloWorld/getMultiResource/js/js33.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js40.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js41.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js42.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js43.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js44.js HTTP/1.1
accept http - /50x.html
recv - /HelloWorld/getMultiResource/js/js33.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js45.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js46.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js47.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js48.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js49.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js50.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js51.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js52.js HTTP/1.1
accept http - /50x.html
send - /HelloWorld/getMultiResource/js/js45.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js53.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js54.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js55.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js56.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js57.js HTTP/1.1
accept http - /50x.html
recv - /HelloWorld/getMultiResource/js/js45.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js58.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js59.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js60.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js61.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js62.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js63.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js64.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js65.js HTTP/1.1
accept http - /50x.html
send - /HelloWorld/getMultiResource/js/js58.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js66.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js67.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js68.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js69.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js70.js HTTP/1.1
accept http - /50x.html
recv - /HelloWorld/getMultiResource/js/js58.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js71.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js72.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js73.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js74.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js75.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js76.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js77.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js78.js HTTP/1.1
accept http - /50x.html
send - /HelloWorld/getMultiResource/js/js71.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js79.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js80.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js81.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js82.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js83.js HTTP/1.1
accept http - /50x.html
recv - /HelloWorld/getMultiResource/js/js71.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js84.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js85.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js86.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js87.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js88.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js89.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js90.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js91.js HTTP/1.1
accept http - /50x.html
send - /HelloWorld/getMultiResource/js/js84.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js92.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js93.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js94.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js95.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js96.js HTTP/1.1
accept http - /50x.html
recv - /HelloWorld/getMultiResource/js/js84.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js97.js HTTP/1.1
accept http - /HelloWorld/getMultiResource/js/js98.js HTTP/1.1
accept http - /50x.html
accept http - /HelloWorld/getMultiResource/js/js99.js HTTP/1.1
accept http - /50x.html
send - /HelloWorld/getMultiResource/js/js97.js HTTP/1.1
recv - /HelloWorld/getMultiResource/js/js97.js HTTP/1.1
accept http - /favicon.ico HTTP/1.1
send - /favicon.ico HTTP/1.1
recv - /favicon.ico HTTP/1.1

我们来看一下这里请求成功的这一部分请求

完

以上是关于09 nginx 中 upstream max_conns 配置为 1, 导致的一部分静态资源请求成功, 一部分静态资源请求失败的主要内容，如果未能解决你的问题，请参考以下文章

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