[SERVER-24270] "chunk too big to move" and "chunk not full enough to trigger auto-split" Created: 24/May/16  Updated: 25/May/16  Resolved: 25/May/16

Status: Closed
Project: Core Server
Component/s: Sharding
Affects Version/s: 3.2.5, 3.2.6
Fix Version/s: None

Type: Bug Priority: Major - P3
Reporter: xihui he Assignee: Unassigned
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Duplicate
duplicates SERVER-19919 Chunks that exceed 250000 docs but ar... Closed
Operating System: ALL
Participants:

 Description   

When I tried to convert a huge collection (about 0.4 billion records) to a sharding collection, I found it could not move the chunks and could not split the chunks.

When the balance tried to move the chunk, I got the following error:

2016-05-24T15:22:52.418+0800 I SHARDING [Balancer] moveChunk result: { chunkTooBig: true, estimatedChunkSize: 33553905, ok: 0.0, errmsg: "chunk too big to move" }
2016-05-24T15:45:26.569+0800 W SHARDING [conn132080234] cannot move chunk: the maximum number of documents for a chunk is 250001 , the maximum chunk size is 67108864 , average document size is 133. Found 252289 documents in chunk

When it tried to split the chunk, I got the following error:

2016-05-24T15:22:52.530+0800 I SHARDING [Balancer] split results: CannotSplit: chunk not full enough to trigger auto-split

I use default chunk size 64MB.

mongos> db.settings.find()
{ "_id" : "chunksize", "value" : NumberLong(64) }

It seems that it fails to move because the record count is > 250001, and fails to split because the chunk size is not large enough?

My mongodbs version are 3.2.5 and 3.2.6.



 Comments   
Comment by Ramon Fernandez Marina [ 25/May/16 ]

Thanks for the update bydsky. I'm going to close this ticket as a duplicate of SERVER-19919 – feel free to watch that ticket for updates and vote for it.

Regards,
Ramón.

Comment by xihui he [ 25/May/16 ]

ramon.fernandez We use wiredTiger. I think the issue is exactly the same as SERVER-19919. I tried to reduce the chunk size to 30M and it's starting to split and move now. Thanks very much.

Comment by Ramon Fernandez Marina [ 24/May/16 ]

bydsky, please take a look at SERVER-19919, which I think describes the exact behavior you're seeing. That ticket also contains a possible workaround that you may want to try.

One quick question though: which storage engine are you using? WiredTiger or MMAPv1?

Thanks,
Ramón.

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