I am using MongoDB 6 (7 nodes, read only, not sharded) and have the logs set to record queries that take over 100 ms. The query below appears quite a bit.
I read the docs for config.system.sessions and I guess it’s syncing the sessions from in memory to the database. Are there ways to optimise this operation?
{"t":{"$date":"2024-01-12T12:00:58.600+00:00"},"s":"I", "c":"COMMAND", "id":51803, "ctx":"conn3885","msg":"Slow query",
"attr":{"type":"command","ns":"config.$cmd","command":{"update":"system.sessions","ordered":false,"writeConcern":
{"w":"majority","wtimeout":15000},"$db":"config"},"numYields":0,"reslen":644,"locks":{"ParallelBatchWriterMode":{"acquireCount":
{"r":928}},"FeatureCompatibilityVersion":{"acquireCount":{"w":928}},"ReplicationStateTransition":{"acquireCount":{"w":928}},"Global":
{"acquireCount":{"w":928}},"Database":{"acquireCount":{"w":928}},"Collection":{"acquireCount":{"w":928}},"Mutex":{"acquireCount":
{"r":928}}},"flowControl":{"acquireCount":928,"timeAcquiringMicros":661},"writeConcern":
{"w":"majority","wtimeout":15000,"provenance":"clientSupplied"},"storage":{"data":
{"bytesRead":15619,"timeReadingMicros":22}},"remote":"$IP","protocol":"op_msg","durationMillis":109}}
Same error listed here I think: Getting too many slow queries on system.session which impacts mongo db performance as well