how to do nginx rewrites from a url with get parameters

Question

This is my first ever StackOverflow question so please bear with me.

Nginx serves many different sites for us and we have a lot of redirects from migrating clients from different vendors and such. We have set up an /includes directory that houses redirect files for each domain that we migrate over. Occasionally, we will need to write redirects from a url that contains get parameters:

http://example.com/content/default.aspx?NewsId=28

To do this, we have been doing this in an nginx /includes file called example.com-redirects

location ^~ /content/default.aspx {
    if ($args ~ "NewsId=28") { rewrite ^ http://example.com/news? permanent; break; }
    # add more statements like the one above
}

That has worked just fine for us thus far. Unfortunately, we need to do the same thing but for a different domain that could have the same get parameters. And of course nginx doesn't allow for duplicate locations.

location ^~ /content/default.aspx {
    if ($args ~ "NewsId=28") { rewrite ^ http://differentexample.org/news? permanent; break; }
}

I've tried a couple of different solutions all giving me syntax errors. No one at my company is an nginx expert anymore so I could really use some help solving this. I have added an if ($host ~ "example.com") within the location block and that gave me an error. And I've tried adding the location block within the if ($host ~ "example.com") block. Both times nginx told me that I can't put that there.

I usually find my answer in the vast knowledge base that is the internet but seem to be striking out on a solution for this and we're running out of time before we launch this client.

Answer 1

Instead of using if, use a variable. In the virtual host config you set this variable. In the include with the location you use it:

server {
    ...
    set $redirect_host "example.org";
    include /includes/news28.conf;
    ...
}

# include part
location /foo {
    if ($args ~ "NewsId=28") { rewrite $scheme://$redirect_host/news? permanent; }
}

Of course you need to set that variable also in the server config of the host already using this include. Hope this helps.