Please see attached graphs showing behavior on our 2.8.0rc1 (mmapv1) replica set.

We experienced the following series of events:

• Rapidly climbing replication lag on both secondaries. Observed IOPS on the secondaries was very high.
• Getmore counter dropped off to zero on the primary
• Restarted one secondary (onprem-2). On restart, its replication lag fell off immediately back down to zero.
• Getmore counter on primary started looking more normal
• Attempted to shutdown the other secondary (onprem-3). It would not shutdown. gdb dump attached.
• After hard killing the other secondary and restarting it's replication lag also fell off to zero.

Will link to logs for all nodes.