Sharing a request id between Apache logs and Mojolicious logs

[robrwo]

Apache has the ability to generate a unique id for each request, and include it in the logs. This request id can be saved in your Apache logs and passed to a Mojolicious application behind a reverse proxy, so that you can connect a specific request in your application logs with a request in your Apache logs.

In Apache configuration, enable mod_unique_id

LoadModule unique_id_module modules/mod_unique_id.so

then add a custom log that includes the unique id:

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\" %{UNIQUE_ID}e" combined_id

...

CustomLog logs/access.log combined_id

In your reverse proxy configuration, add a header with the unique id:

  ProxyPass http://localhost:8080 retry=0
  ...
  RequestHeader set X-UID "%{UNIQUE_ID}e"
  ProxyPassReverse http://localhost:8082

Then update your Mojolicious application to use the request id from Apache:

$self->hook(
    before_dispatch => sub ($c) {
        if ( my $id = $c->req->headers->header('X-UID') ) {
            $c->req->request_id($id);
        }
    }
);

[s1037989]

This is awesome. I use nginx. I'll need to investigate doing something similar for that, and your contributions should provide some great direction for how to possibly go about it.

But, more importantly, thanks for sharing the idea and implementation on the discussion boards. It's really great to see discussion like this here!