Hi:

   I had found my MongoDB secondary node get a stuck, the oplog applyOps can't work. The pstack showed that WiredTiger is busy for eviction.

   I suspected the bug in the WiredTiger Engine. I wrote a corner case for WiredTiger. I found the WiredTiger will get stuck when the cache is small and get a heavy workload(multi-thread write + multi-thread scan). 

   I can upload my test case and WT stat file for you.