2016-08-03T14:58:46.111+0000 I COMMAND [conn23] command local.oplog.rs command: collStats { collstats: "oplog.rs" } keyUpdates:0 writeConflicts:0 numYields:0 reslen:4786 locks:{ Global: { acquireCount: { r: 2 }, acquireWaitCount: { r: 1 }, timeAcquiringMicros: { r: 252271 } }, Database: { acquireCount: { r: 1 }, acquireWaitCount: { r: 1 }, timeAcquiringMicros: { r: 85 } }, oplog: { acquireCount: { r: 1 } } } protocol:op_query 253ms
2016-08-03T14:58:46.187+0000 I COMMAND [conn66] command admin.$cmd command: listDatabases { listDatabases: 1.0 } keyUpdates:$ writeConflicts:0 numYields:0 reslen:721 locks:{ Global: { acquireCount: { r: 22 }, acquireWaitCount: { r: 6 }, timeAcquiringMicros: { r: 8576 } }, Database: { acquireCount: { r: 11 }, acquireWaitCount: { r: 1 }, timeAcquiringMicros: { r: 66 } } } protocol:op_command 1830ms
root@slow-mongo-server:/db# mongostat 5 insert query update delete getmore command % dirty % used flushes vsize res qr|qw ar|aw netIn netOut conn set repl time *27 *0 *103 *0 0 3|0 1.1 26.7 0 12.9G 12.3G 0|0 0|0 457b 5k 14 api_a SEC 2016-08-03T15:08:10Z *25 *0 *135 *0 0 3|0 0.8 26.7 1 12.9G 12.3G 0|0 0|0 349b 5k 14 api_a SEC 2016-08-03T15:08:15Z *21 *0 *110 *0 0 6|0 0.3 26.7 0 12.9G 12.3G 0|0 0|0 647b 15k 14 api_a SEC 2016-08-03T15:08:20Z *30 *0 *123 *0 0 3|0 0.4 26.7 0 12.9G 12.3G 0|0 0|0 349b 5k 14 api_a SEC 2016-08-03T15:08:25Z *17 *0 *100 *0 0 3|0 0.5 26.7 0 12.9G 12.3G 0|0 0|0 402b 5k 14 api_a SEC 2016-08-03T15:08:30Z
Hi Ofer,
Apart from the queries reported in the log file, are you experiencing any performance issue on the replica set? Also, are the logs snippet and mongostat from the secondary you upgraded to WiredTiger?
The main role of a secondary in a replica set is to provide high availability by performing the operations of the primary node as quickly as possible. This is to ensure that if the primary goes offline, a secondary can instantly replace the primary. Therefore, for a secondary node, the most important metric is how far behind the primary it is in terms of writes.
This can be done by checking rs.printSlaveReplicationInfo()
which shows how far is a secondary behind the primary.
Regards,
Amar