[SERVER-36017] Balancer doesn't migrate chunks Created: 09/Jul/18  Updated: 14/Aug/18  Resolved: 09/Jul/18

Status: Closed
Project: Core Server
Component/s: Sharding
Affects Version/s: 3.6.5
Fix Version/s: None

Type: Question Priority: Major - P3
Reporter: Changmin Keum [X] Assignee: Ramon Fernandez Marina
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:

 Description   

We have upgraded MongoDB sharded cluster from 2.0 to 3.6 in the past 6 months.

And then, we enabled balancer, but no chunk migration occurred for 5 hours.

After we enabled blancer, primary config server logged,

2018-XX-XXT09:36:39.007+0900 I SHARDING [Balancer] Refreshing chunks for collection db.sharded-collection based on version 0|0||000000000000000000000000
2018-XX-XXT09:36:39.103+0900 I SHARDING [ConfigServerCatalogCacheLoader-1] Refresh for collection db.sharded-collection took 95 ms aand found version 7|27819||5a66b9b7eb81557948d33b6f  
 
2018-XX-XXT13:50:29.159+0900 I SHARDING [Balancer] Refreshing chunks for collection db.sharded-collection based on version 7|27819||5a66b9b7eb81557948d33b6f
2018-XX-XXT13:50:29.164+0900 I SHARDING [ConfigServerCatalogCacheLoader-2] Refresh for collection db.sharded-collection took 4 ms and found version 7|27819||5a66b9b7eb81557948d33b6f  

 Our dev MongoDB cluster's primary config server logged "version 22" and it migrates chunks well.

Currently, balancer is disabled. We have never used balancer before. So, chunks are quite unevenly distributed.

I attached our server's stats. No jumbo chunk exists. Any guesses on what blocks balancer's chunk migration and possible solution?

 



 Comments   
Comment by Ramon Fernandez Marina [ 09/Jul/18 ]

Thanks for your report Changmin. Please note that the SERVER project is for reporting bugs or feature suggestions for the MongoDB server. For MongoDB-related support discussion please post on the mongodb-user group or Stack Overflow with the mongodb tag, where your question will reach a larger audience. A question like this involving more discussion would be best posted on the mongodb-user group. See also our Technical Support page for additional support resources.

Regards,
Ramón.

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