Snap: Startup failure due to MongoDB's real spinup time

Description:

Snap: RocketChat startup timings -> not really waiting for MongoDB

Steps to reproduce:

MongoDB writes PID-File, but needs more time to really startup

Mai 05 03:00:41 rocket rocketchat-server.rocketchat-mongo[685]: 2019-05-05T03:00:41.688+0200 I CONTROL [initandlisten] MongoDB starting : pid=788 port=27017 dbpath=/var/snap/rocketchat-server/common 64-bit host=rocket

Mai 05 03:01:19 rocket rocketchat-server.rocketchat-mongo[685]: 2019-05-05T03:01:19.423+0200 I REPL [rsSync] transition to primary complete; database writes are now permitted

RC's Snap Startup Script startRocketChat waits only for PID, but not if a connection could made up, resulting in:

startup_log.txt

Expected behavior:

RC should really wait for MongoDB-Connection.

Actual behavior:

RC does not start.

Server Setup Information:

• Version of Rocket.Chat Server: 0.74.3
• Operating System: Debian 9.9
• Deployment Method: snap
• Number of Running Instances: 1
• DB Replicaset Oplog: 1
• NodeJS Version: 8.11.3 - x64
• MongoDB Version: 3.2.7

Start with .snapcraft/resources/startRocketChat and compare its startup checks with the MongoDB log timings in the issue. Reproduce the snap startup sequence using the provided startup log and verify that Rocket.Chat starts only after MongoDB accepts connections, not merely after its PID file appears.