Inherit proxy_set_header when using it in location block

Question

I am trying to set up a bunch of virtual hosts on Nginx and I want to set some headers before passing the request upstream. I have some headers that I always want to set and then I have some headers that I want to set for selected location blocks.

Unfortunately, it seems that Nginx does not allow the proxy_set_header directive on multiple levels and as a result, it just clears any headers set in the http block.

Nginx documentation states the following on proxy_set_header:

Allows redefining or appending fields to the request header passed to the proxied server. The value can contain text, variables, and their combinations. These directives are inherited from the previous level if and only if there are no proxy_set_header directives defined on the current level.

So the question is... either Nginx has a disappointing limitation or I am thinking about this problem in the wrong way.

Any ideas on an idiomatic solution to this problem?

Answer 1

Create a file to include in each block that sets the headers you want. (So a common inc-http-headers.conf) that you include in the http block and all of the location blocks that need the common headers.

Answer 2

If you are using OpenResty or at least its headers-more-nginx-module, you can do this with the more_set_input_headers directive.

For example, the following will do what you expect:

http {
    # ...
    more_set_input_headers "Foo: 1";
    server {
        # ...
        more_set_input_headers "Bar: 2";
        location / {
            more_set_input_headers "Qux: 3";
            proxy_pass http://some-server;
            # request to some-server has Foo: 1, Bar: 2, and Qux: 3
        }
    }
}

There are some quirks to this approach however. You cannot alter the Connection or Host headers this way and you may need to be careful when nginx's own caching is enabled and you're modifying cache-related headers. If you aren't concerned with cache-related headers, then the biggest places these limitations crop up are: 1) getting WebSockets to work and 2) with upstreams that use the Host header in a nontrivial way.

Consequentially, a good rule of thumb I've found is to use proxy_set_header for Connection and Host and more_set_input_headers for everything else.