Nginx failover without load balancing

configurationfailoverload balancingnginxreverse-proxy

I'm having trouble configuring nginx.

I'm using nignx as a reverse proxy. I want to send my all requests to my first server. If the first server is down, I want to send requests to second server.

In short, how can I have a failover solution without load balancing?

Best Answer

What you want is an active+passive setup. Here's an example nginx conf snippet to get you going:

upstream backend {
    server 1.2.3.4:80 fail_timeout=5s max_fails=3;
    server 4.5.6.7:80 backup;
}

server {
    listen 80;
    server_name whatevs.com;

    location / {
        proxy_pass http://backend;
    }
}

So, 'normally', all requests will go to host 1.2.3.4. If we get three failures to that box, then 4.5.6.7 will take over.

Related Solutions

Nginx – How to Set Up as a Caching Reverse Proxy

I don't think that there is a way to explicitly invalidate cached items, but here is an example of how to do the rest. Update: As mentioned by Piotr in another answer, there is a cache purge module that you can use. You can also force a refresh of a cached item using nginx's proxy_cache_bypass - see Cherian's answer for more information.

In this configuration, items that aren't cached will be retrieved from example.net and stored. The cached versions will be served up to future clients until they are no longer valid (60 minutes).

Your Cache-Control and Expires HTTP headers will be honored, so if you want to explicitly set an expiration date, you can do that by setting the correct headers in whatever you are proxying to.

There are lots of parameters that you can tune - see the nginx Proxy module documentation for more information about all of this including details on the meaning of the different settings/parameters: http://nginx.org/r/proxy_cache_path

http {
  proxy_cache_path  /var/www/cache levels=1:2 keys_zone=my-cache:8m max_size=1000m inactive=600m;
  proxy_temp_path /var/www/cache/tmp; 


  server {
    location / {
      proxy_pass http://example.net;
      proxy_cache my-cache;
      proxy_cache_valid  200 302  60m;
      proxy_cache_valid  404      1m;
    }
  }
}

Nginx – How to Reply with 200 Without Serving a File

Yes, you can

location / {
    return 200 'gangnam style!';
    # because default content-type is application/octet-stream,
    # browser will offer to "save the file"...
    # if you want to see reply in browser, uncomment next line 
    # add_header Content-Type text/plain;
}

Best Answer

Related Solutions

Nginx – How to Set Up as a Caching Reverse Proxy

Nginx – How to Reply with 200 Without Serving a File

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