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503 Service Temporarily Unavailable 

最近网站刷新后经常出现503 Service Temporarily Unavailable错误，有时有可以，联想到最近在nginx.conf里做了单ip访问次数限制，(limit_req_zone $binary_remote_addr zone=allips:20m rate=20r/s;) 把这个数量放大后在刷新发现问题解决。（还顺便把这个改大了 limit_req zone=allips burst=50 nodelay;   ）为了证实该问题，反复改动该数量测试发现问题确实在这。这个数量设得太小有问题，通过fiddler发现web页面刷新一下，因为页面上引用的js,css,图片都算一个连接。所以单个页面刷新下就有可能刷爆这个限制，超过这个限制就会提示503 Service Temporarily Unavailable。

附上nginx.conf
#user  nobody;
 worker_processes  1;
 #worker_rlimit_nofile 100000; 
 #error_log  logs/error.log;
 #error_log  logs/error.log  notice;
 #error_log  logs/error.log  info;

 #pid        logs/nginx.pid;

 events {
     worker_connections  1024;
 }

 http {
     include       mime.types;
     default_type  application/octet-stream;

 ##cache##
   proxy_connect_timeout 5;
   proxy_read_timeout 60;
   proxy_send_timeout 5;
   proxy_buffer_size 16k;
   proxy_buffers 4 64k;
   proxy_busy_buffers_size 128k;
   proxy_temp_file_write_size 128k;
   proxy_temp_path /home/temp_dir;
   proxy_cache_path /usr/local/nginx/cache levels=1:2 keys_zone=cache_one:200m inactive=1d max_size=30g;
   ##end##
 #limit per ip per second access times 10 
 limit_req_zone $binary_remote_addr zone=allips:20m rate=20r/s;

     #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
     #                  '$status $body_bytes_sent "$http_referer" '
     #                  '"$http_user_agent" "$http_x_forwarded_for"';

     #access_log  logs/access.log  main;

     sendfile        on;
     #tcp_nopush     on;

     #keepalive_timeout  0;
     keepalive_timeout  65;

     #gzip  on;
 upstream myweb80{
    ip_hash;
    server 192.168.3.105:80;
    server 192.168.3.103:80;
 }

 upstream myweb8080{
    ip_hash;
    server 192.168.3.222:10080;
    #server 192.168.3.103:8080;
  } 
 upstream myweb10086{
    ip_hash;
    server 192.168.3.102:10086;
    server 192.168.3.108:10086;
  } 
 upstream myweb443{
    ip_hash;
    server 192.168.3.105:443;
    server 192.168.3.103:443;
  } 

     # another virtual host using mix of IP-, name-, and port-based configuration
     #
    server {
         listen       80;
         allow   218.17.158.2;
 allow 127.0.0.0/24;
 allow 192.168.0.0/16;
 allow 58.251.130.1;
 allow 183.239.167.3;
 allow 61.145.164.1;
 deny    all;
 server_name  myweb.com;
         location / {
                 proxy_pass http://myweb80;
 proxy_set_header  X-Real-IP  $remote_addr;
 limit_req zone=allips burst=50 nodelay;    
         }
     }

     server {
         listen       8080;
 allow   218.17.158.2;
 allow 127.0.0.0/24;
 allow 192.168.0.0/16;
 allow 58.251.130.1;
 allow 183.239.167.3;
 allow 61.145.164.1;
 deny    all;
         location / {
                 proxy_pass http://myweb8080;
 proxy_set_header  X-Real-IP  $remote_addr;
 limit_req zone=allips burst=50 nodelay;    
         }
     }

 # HTTPS server
     #
     server {
         listen       10086 ssl;
         server_name  localhost;
 allow   218.17.158.2;
 allow 127.0.0.0/24;
 allow 192.168.0.0/16;
 allow 58.251.130.1;
 allow 183.239.167.3;
 allow 61.145.164.1;
 #deny    all;
        ssl_certificate      ssl/1_www.myweb.com_bundle.crt;
         ssl_certificate_key  ssl/2_www.myweb.com.key;

     #    ssl_session_cache    shared:SSL:1m;
     #    ssl_session_timeout  5m;

     #    ssl_ciphers  HIGH:!aNULL:!MD5;
     #    ssl_prefer_server_ciphers  on;

         location / {
      proxy_pass   https://myweb10086;
       #       root   html;
       #     index  index.html index.htm;
         }
     }

     server {
         listen       443 ssl;
         server_name  localhost;

        ssl_certificate      ssl/1_www.myweb.com_bundle.crt;
         ssl_certificate_key  ssl/2_www.myweb.com.key;

     #    ssl_session_cache    shared:SSL:1m;
     #    ssl_session_timeout  5m;

     #    ssl_ciphers  HIGH:!aNULL:!MD5;
     #    ssl_prefer_server_ciphers  on;

         location / {
      proxy_pass   https://myweb443;
       #       root   html;
       #       root   html;
       #     index  index.html index.htm;
         }
     }
 }