fix(shutdown): kill server after timeout when hanging on shutdown

When socket.io is not able to close a connection somehow, the code
never reaches the final shutdown state but keeps waiting for all
connections to be closed. This can cause a high CPU load on failing
shutdown. It is very unlikely to happen, except when the server is
shut down exactly at the same time a socket is disconnecting and not
already marked as disconnected. This change adds a fallback timer
which forcefully kills the server after a certain amount of time.

Signed-off-by: Erik Michelson <github@erik.michelson.eu>

app.js

@@ -394,6 +394,13 @@ function handleTermSignals () {
           process.exit(0)
         }
       })
+    } else {
+      logger.warn(`Real time server not ready for shutdown, trying again (${currentCleanTry}/${maxCleanTries})...`)
+      currentCleanTry++
+      if (currentCleanTry > maxCleanTries) {
+        logger.error('Could not save note revisions after shutdown! Exiting.')
+        process.exit(1)
+      }
     }
   }, 200)
 }