[SERVER-14733] How to check which sql statement is causing global lock Created: 30/Jul/14  Updated: 10/Dec/14  Resolved: 31/Jul/14

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Question Priority: Major - P3
Reporter: Sarbamangal Choudhury Assignee: Stennie Steneker (Inactive)
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:

 Description   

We are monitoring MongoDB using MMS and getting global lock for 10-15 sec alert. I like to see which sql is causing this global lock. I have checked all the sql in log file, but can't find any sql which is taking so long.



 Comments   
Comment by Stennie Steneker (Inactive) [ 31/Jul/14 ]

Hi Sarbamangal,

The SERVER project is intended to be used for reporting bugs or feature suggestions for the MongoDB server.

In future, please post MongoDB-related support questions like this on the mongodb-users group (http://groups.google.com/group/mongodb-user) or Stack Overflow / ServerFault. MongoDB team members are active in these forums, and you can also benefit from the experience of other MongoDB users.

If you have configured an alert based on lock percentage in MMS you also need to consider an appropriate threshold – lock % does not necessarily indicate a performance problem, and will occur as a result of normal write activity. You need to look at other possible correlations in MMS such as the opcounters, queues, background flush, page faults, and I/O at the time.

Some further resources that may help:

  • The MongoDB Query profiler can be enabled on a per-database level to help you track down slow queries. Slow queries are also included in the mongod log.
  • A recent presentation on Diagnostics & Debugging provides some helpful insight into troubleshooting, and in particular doing log-based analysis using mtools.

Regards,
Stephen

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