I have an instance of Discourse running in a Docker container with the prometheus-exporter installed. We are using
bundle exec rails server -b 0.0.0.0 to start the rails server (using /bin/unicorn/ gives the same error) and have specified the port mapping
9045:9045 and exposed port 9045.
The puma error logs show the following errors:
Prometheus Exporter, failed to send message Cannot assign requested address - connect(2) for "localhost" port 9405
2022-08-09 22:48:25 +0000 Rack app ("GET /metrics" - (172.22.0.1)): #<Errno::EADDRNOTAVAIL: Failed to open TCP connection to localhost:9405 (Cannot assign requested address - connect(2) for "localhost" port 9405)>
Is there something special Discourse normally does with puma to ensure that the prometheus-exporter can open a TCP connection on port 9405?