我们在使用nginx的时候有不少问题出现，首先我们就来解决下nginx 502错误的问题

经 过分析将nginx的error log打开，发现”pstream sent too big header while reading response header from upstream”这样的错误提示，查阅了一下资料，大意是nginx缓冲区有一个bug造成的,我们网站的页面消耗占用缓冲区可能过大

我们是nginx反向代理
proxy是nginx作为client转发时使用的，如果header过大，超出了默认的1k，就会引发上述的upstream sent too big header （说白了就是nginx把外部请求给后端apache ，apache返回的header  太大nginx处理不过来就导致了。

server {
        listen       80;
        server_name  *.xywy.com ;

       large_client_header_buffers 4 16k;

       #charset koi8-r;

       # access_log off;

       location / {

#添加这3行 ，
                proxy_buffer_size 64k;
                proxy_buffers   32 32k;
                proxy_busy_buffers_size 128k;

          proxy_set_header Host $host;
           proxy_set_header X-Real-IP       $remote_addr;
           proxy_set_header X-Forwarded-For  $proxy_add_x_forwarded_for;

          set $baiduspider '';

          if ( $http_user_agent ~ Baiduspider) {
              set $baiduspider Baidu;
          }

............

如果是 nginx+PHPcgi 就该 

fastcgi_connect_timeout 60;
fastcgi_send_timeout 180;
fastcgi_read_timeout 180;
fastcgi_buffer_size 128k;
fastcgi_buffers 4 256k;
fastcgi_busy_buffers_size 256k;
fastcgi_temp_file_write_size 256k;
fastcgi_intercept_errors on
011/01/07 11:12:57 [error] 10770#0: *38585340 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 116.22.131.154, server: *.xywy.com, request: "GET /ysmp/index.php?did=124994 HTTP/1.0", upstream: "http://127.0.0.1:8080/ysmp/index.php?did=124994", host: "xywy.yn16.com"
 

后来原来那错误没了出了新错误了 upstream timed out 超时？

server {
        listen       80;
        server_name  *.xywy.com ;
  large_client_header_buffers 4 16k;
        client_max_body_size 300m;
        client_body_buffer_size 128k;
        proxy_connect_timeout 600;
        proxy_read_timeout 600;
        proxy_send_timeout 600;
                proxy_buffer_size 64k;
                proxy_buffers   4 32k;
                proxy_busy_buffers_size 64k;
            

关键词：nginx