Hi all

There is a replica set with 2 mongod nodes and 1 arbiter. It is 2000 average updates on master node by mongostat.

All of mongodb oplog: 10g
Master syncdelay: 100s
Secondary syncdelay: 150s

At the request peak, secondary node reports "syncing to: 10.136.24.88:27032" on MongoDB web interface. A monment later, it reports "too stale to catch up". I found that some informations from secondary log, but the network is well because all of nodes are at LAN.

Mon Aug 27 13:10:37 [rsSync] Socket recv() timeout 10.136.24.88:27032
Mon Aug 27 13:10:37 [rsSync] SocketException: remote: 10.136.24.88:27032 error: 9001 socket exception [3] server [10.136.24.88:27032]
Mon Aug 27 13:10:37 [rsSync] DBClientCursor::init call() failed
Mon Aug 27 13:10:38 [rsSync] replSet syncing to: 10.136.24.88:27032

Also I found that the optime of secondary oplog would not be updated when secondary node reports "syncing to: 10.136.24.88:27032" on MongoDB web interface.

I tested MongoDB 2.0.6/2.0.7 to reproduct it.