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sweb
Asked: 2016-01-31 02:38:50 +0800 CST

nginx use proxy cache if backend is down

  • 772

I need to nginx proxy use cache if backend server down:

this is my configuration. but seems be nginx use cache without check backend server.

http {

  # ...

  proxy_set_header Host $host;
  proxy_set_header X-Real-IP $remote_addr;
  proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  proxy_cache_path /tmp/nginx levels=1:2 keys_zone=tmpzone:10m inactive=60m;
  proxy_cache_key "$scheme$request_method$host$request_uri";


  server {
    server_name _;

    location / {
      proxy_connect_timeout 5s;
      proxy_read_timeout 5s;
      proxy_cache tmpzone;
      proxy_cache_valid      200 304 1d;
      proxy_cache_use_stale  error timeout invalid_header updating http_500 http_502 http_503 http_504;
      proxy_set_header X-Real-IP  $remote_addr;
      proxy_set_header X-Forwarded-For $remote_addr;
      proxy_set_header Host 'www.example.com';
      proxy_pass http://www.example.com;
    }
  }
}

Question is how can i bypass the proxy cache if backend server is up ? And when backend server is up my proxy server dont use cache at all.

nginx

2 Answers

  1. Seems a duplicate of this:

    https://stackoverflow.com/questions/16756271/how-to-configure-nginx-to-serve-cached-content-only-when-backend-is-down-5xx-re

    In short, use proxy_cache_use_stale

    As an update, i tested this and it works fine. I did the test in my workstation where i have (for completeness):

    Fedora 23 nginx 1.8.1 configured as ssl terminator + cache + reverse proxy Apache 2.4.18 configured to listen at port 80

    With apache acting as upstream, serving just a static file i did this test:

    1. Apache up, nginx up, pointing the browser to the reverse proxied URL served by nginx i see the proxied content from Apache. At this point nginx keeps this on cache.
    2. Stopped apache
    3. connecting to nginx i see the cached file as served before by Apache.

    The nginx config i used is (only the interesting parts):

    nginx.conf :

    http {
[...]
location
    proxy_cache_path        /var/lib/nginx/tmp/proxy/ levels=1:2 keys_zone=STATIC:10m inactive=24h max_size=1g;
    include /etc/nginx/conf.d/*.conf;
}

    /etc/nginx/conf.d/local.conf :

    upstream localhost {
    server 127.0.0.1:80;
[...]
}


server {
    listen       127.0.0.1:443 ssl;

[...]

    location /be/ {
        proxy_pass              http://localhost;
        proxy_cache             STATIC;
        proxy_cache_valid       200 1d;
        proxy_cache_use_stale   error;
}
    • 8

  2. Use proxy_intercept_errors and proxy 500s to a server that has caching enabled.

    • 0