With mloginfo
I found a strange log entry. Didn't find anything about it in MongoDB docs and other related sites.
$ mloginfo mongodb.log --distinct
source: mongodb.log
host: example
start: 2016 Aug 25 14:57:57.630
end: 2016 Aug 26 08:02:05.751
date format: iso8601-local
length: 572308
binary: mongod
version: 3.2.8
storage: wiredTiger
DISTINCT
28069 connection accepted from ... # ... ( ... now open)
27587 end connection ... ( ... now open)
15 exception: ... on:
10 serverStatus was very slow:
4 task: ... took: ... ms
3 killcursors: found ... of
3 SocketException handling request, closing client connection:
1 git version:
1 waiting for connections on port
what is that exactly? What is a PeriodicTaskRunner
and what does UnusedLockCleaner
do? Any actions required from DBA?
2016-08-25T21:03:38.449+0200 I COMMAND [PeriodicTaskRunner] task: UnusedLockCleaner took: 105ms
2016-08-26T00:21:40.285+0200 I COMMAND [PeriodicTaskRunner] task: UnusedLockCleaner took: 184ms
2016-08-26T01:25:40.940+0200 I COMMAND [PeriodicTaskRunner] task: UnusedLockCleaner took: 273ms
2016-08-26T01:55:41.357+0200 I COMMAND [PeriodicTaskRunner] task: UnusedLockCleaner took: 234ms
Best Answer
The nice part about MongoDB is that it is open source, so your answer is in the code, starting with comments about UnusedLockCleaner:
Then taking a look at the
lock_manager
code we get more info about the cleanup function:Basically it looks like some background maintenance being done by the database to clear out unused locks and keep the memory usage of the lock manager under control. Nothing to be concerned about, since if the database is busy and the locks are in use they won't be cleaned up. If you are seeing (reproducible) issues with it, then it would be best to open a ticket to debug with the developers, since this would not be intended.