We are running MongoDB 3.2.12 three replica set on dockers on Redhat Linux 4.1.12-61.1.25.el7uek.x86_64. It has happened a few times recently that our apps all a sudden could not connect to the set any more (mark this #1 for reference). I went on the primary node, and could not get into mongo shell to the primary, I could still get in to the two secondaries. And the replication seems still fine (I checked with db.printSlaveReplicationInfo()).

One other strange thing I noticed is the MongoDB log file stopped being updated on the primary (mark this #2 for reference). It was fine on secondaries. This does not seem to be directly related with the above main issue. It could take days for #1 to happen after #2 happened from recent observations.

Could you help? We are at a loss and don't know what to look for.

Thanks,

Erin