Configure Systemd Socket Activation

as new way for Poseidon to accept connections. This should reduce our issues caused by deployments.

cmd/poseidon/main.go

@@ -208,9 +208,9 @@ func serveHTTPListener(server *http.Server, l net.Listener) {
 	}
 
 	if errors.Is(err, http.ErrServerClosed) {
-		log.WithError(err).WithField("listener", l).Info("Server closed")
+		log.WithError(err).WithField("listener", l.Addr()).Info("Server closed")
 	} else {
-		log.WithError(err).WithField("listener", l).Error("Error during listening and serving")
+		log.WithError(err).WithField("listener", l.Addr()).Error("Error during listening and serving")
 	}
 }
 

docs/configuration.md

@@ -29,6 +29,12 @@ If a value is not specified, the value of the subsequent possibility is used.
 
 - Again, this can be overwritten by the environment variable `POSEIDON_SERVER_PORT`, e.g., using `export POSEIDON_SERVER_PORT=5000`.
 
+### Systemd
+
+Poseidon can be configured to run as a systemd service. Poseidon can optionally also be configured to use a systemd socket.
+The use of systemd provides capabilities for managing Poseidon's state and zero downtime deployments.
+Minimal examples for systemd configurations can be found in `.github/workflows/resources`.
+
 
 ## Nomad