Should I use rewrite or return or proxy_pass in nginx?

Question

The Apache documentation pretty clearly states that mod_rewrite should only be a last resort. For nginx, the Pitfalls section has examples where the request_uri is essentially unchanged.

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The situation is this:

• We (a department in an institute) have a main webserver which is due to be upgraded soon (running Debian 6). To deal with the upgrade, I have set up an nginx server, which will proxy parts known to be working fine to an upgraded server and others to the old server.
• The old server had a number of ProxyPass rules (a significant amount of its work is proxying). I wish to shift all of them to nginx, since, as I understand, nginx is more performant in proxying.
• A large number of users have user home directories being served by another server. For these users, but tilde and non-tilde versions are available (i.e., http://my.site/muru and http://my.site/~muru would be proxied to http://other.server/~muru, but http://other.server/muru doesn't exist).
• A number of folders were proxied to a different folder on the same server. (e.g., http://my.site/local-club would be proxied to http://my.site/~local-club).

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My main question is:

• Given A and B both being proxied to C on a different server, should I use rewrite or location with return to redirect requests for B to A, or continue proxying both?
• Given A and B both on the same server, with B being proxied to A, should I use rewrites or returns to redirect B to A?

Redirection (and return) has the benefit of clearly indicating the relation between the two directories.

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My rewrite rules look like:

rewrite ^/B(/.*) /A$1 permanent;

And the return rules:

location ~ ^/B(/.*) {
    return 301 /A$1;
}

With:

location ~ ^/~(A|D|E|F..)/ {
    proxy_pass https://other.server;
    proxy_redirect default;
}

Answer 1

That doesn't really matter execpt if your nginx server will deal with thousands of requests per second and you want to avoid each request to spend CPU time in rewrite regexs matching. Now, I would say use the most clear way to write your configuration files until you reach this limit then if you don't have the budget to scale your infrastructure, it would be time to think about tricking your configuration to fit your traffic. The drawback of return is that if you have multiple redirections you will end up with one location wrapping one return directive. Using rewrites you can wrap multiple of them in one generic location and test in the first parameter for a more specific pattern.

Update : an example of multiple redirection in a generic location :

location /B {
    rewrite ^/B/foo/(.*)$ /A/newfoo/$1 permanent;
    rewrite ^/B/bar/(.*)$ /A/newbar/$2 permanent;
    rewrite ^/B/(.*)$ /A/$1 permanent;
}