Modifying a Location header with nginx proxy_pass - regex

Question

I have an nginx proxy_pass setup to pass every request on /api through to a backend Tomcat REST service. This service in some cases returns a Location header which varies according to the type of request, e.g., Location: http://foo.bar/baz/api/search/1234567 -- the baz part is due to it being hosted on Tomcat.
My current configuration rewrites the foo.bar host name correctly, but leaves the baz part intact. I'd like to strip this, but the proxy_pass options seem to be limited to clearing or setting a new value for the header.
Is there a way to modify headers dynamically before being passed on to the client, using a regex substitute, for instance? This is my nginx configuration:
location /api {
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_max_temp_file_size 0;
client_max_body_size 10m;
client_body_buffer_size 128k;
proxy_connect_timeout 90;
proxy_send_timeout 90;
proxy_read_timeout 90;
proxy_buffers 32 4k;
proxy_redirect off;
proxy_pass http://foo.bar:8080/baz/api;
}

Answer 1

You may be able to use regexp to modify it but a better way is to use a proxy redirect:
proxy_redirect http://foo.bar/baz/ /;
http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_redirect
Any Location headers for foo.bar/baz/ will go to /
If you just want to redirect /baz/api, that'll work too.
If any redirects are also adding the port, you'll need to add http://foo.bar:8080/baz/ as well (separate redirect).
Hope this helps!