How to redirect HTTP request based on URL parameter?

Host-P => App-A,App-B,App-C
Host-Q => App-X,App-Y,App-Z

http://myapp.test.com/?=appType=App-A
http://myapp.test.com/?=appType=App-B

http://myapp.test.com/?=appType=App-Y
http://myapp.test.com/?=appType=App-X

If the query parameter refers to a container that you can address directly, you can just pass that to proxy_pass directly, e.g.:

        proxy_pass http://$arg_appType;

But that’s using untrusted input and is also a massive security hole. Consider ?appType=www.google.com. I show this as an example of what not to do.

---

Instead, use a map to map query parameters to destinations:

map $arg_appType $destination {
    App-A http://container1:8443;
    App-B http://container2:5000;
    App-X http://container24:9001;
    App-X https://some.remote.host;
}

Now you can proxy_pass directly to it.

         proxy_pass $destination;

But you should also intercept the situation in which an unknown or no appType was given.

    if ($destination = "") {
        return 403;    # or do something else appropriate
    }

If you have a specific container to handle that scenario, you can use default in the map to send to it instead.

map $arg_appType $destination {
    ....
    default http://error-handler-container:8000;
}