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Type:
Bug
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Resolution: Done
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Priority:
Major - P3
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None
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Affects Version/s: 5.0.12, 5.0.9
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Component/s: None
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None
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ALL
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When trying to reshard a collection we are getting an error message telling that the sort limit is exceeded.
The resarding command is being run as follows:
[direct: mongos] admin> sh.reshardCollection('database.messages', {_id: 'hashed'}) MongoServerError: Sort exceeded memory limit of 104857600 bytes, but did not opt in to external sorting.
The collection contains approx. 2.4B documents split across 10 shards.
Shard distribution looks like this:
[direct: mongos] database> db.messages.getShardDistribution()
Shard rs06 at rs06/mongo-pm-repl06-1:27018,mongo-pm06:27018
{
data: '78.1GiB',
docs: 360057505,
chunks: 5669,
'estimated data per chunk': '14.1MiB',
'estimated docs per chunk': 63513
}
---
Shard shard0001 at rs02/DS5033:27018,mongo-pm-repl02-1:27018
{
data: '49.25GiB',
docs: 245035457,
chunks: 5670,
'estimated data per chunk': '8.89MiB',
'estimated docs per chunk': 43216
}
---
Shard shard0000 at rs01/DS5032:27018,mongo-pm-repl01-1:27018
{
data: '43.17GiB',
docs: 217760699,
chunks: 5669,
'estimated data per chunk': '7.79MiB',
'estimated docs per chunk': 38412
}
---
Shard rs09 at rs09/mongo-pm-repl09-1:27018,mongo-pm09:27018
{
data: '47.01GiB',
docs: 220116142,
chunks: 5669,
'estimated data per chunk': '8.49MiB',
'estimated docs per chunk': 38828
}
---
Shard rs03 at rs03/mongo-pm-repl03-1:27018,mongo-pm03:27018
{
data: '37.81GiB',
docs: 190704378,
chunks: 5670,
'estimated data per chunk': '6.82MiB',
'estimated docs per chunk': 33633
}
---
Shard rs05 at rs05/DS5085:27018,mongo-pm-repl05-1:27018
{
data: '36.7GiB',
docs: 185097348,
chunks: 5669,
'estimated data per chunk': '6.63MiB',
'estimated docs per chunk': 32650
}
---
Shard rs07 at rs07/mongo-pm-repl07-1:27018,mongo-pm07:27018
{
data: '88.01GiB',
docs: 413919369,
chunks: 5669,
'estimated data per chunk': '15.89MiB',
'estimated docs per chunk': 73014
}
---
Shard rs04 at rs04/mongo-pm-repl04-1:27018,mongo-pm04:27018
{
data: '38.33GiB',
docs: 193215609,
chunks: 5677,
'estimated data per chunk': '6.91MiB',
'estimated docs per chunk': 34034
}
---
Shard rs08 at rs08/mongo-pm-repl08-1:27018,mongo-pm08:27018
{
data: '45.07GiB',
docs: 207666324,
chunks: 5668,
'estimated data per chunk': '8.14MiB',
'estimated docs per chunk': 36638
}
---
Shard rs10 at rs10/mongo-pm-repl10-1:27018,mongo-pm10:27018
{
data: '37.04GiB',
docs: 178733333,
chunks: 2332,
'estimated data per chunk': '16.26MiB',
'estimated docs per chunk': 76643
}
---
Totals
{
data: '7.81030509569951e+100GiB',
docs: 2412306164,
chunks: 53362,
'Shard rs06': [
'0 % data',
'14.92 % docs in cluster',
'232B avg obj size on shard'
],
'Shard shard0001': [
'0 % data',
'10.15 % docs in cluster',
'215B avg obj size on shard'
],
'Shard shard0000': [
'0 % data',
'9.02 % docs in cluster',
'212B avg obj size on shard'
],
'Shard rs09': [
'0 % data',
'9.12 % docs in cluster',
'229B avg obj size on shard'
],
'Shard rs03': [ '0 % data', '7.9 % docs in cluster', '212B avg obj size on shard' ],
'Shard rs05': [
'0 % data',
'7.67 % docs in cluster',
'212B avg obj size on shard'
],
'Shard rs07': [
'0 % data',
'17.15 % docs in cluster',
'228B avg obj size on shard'
],
'Shard rs04': [ '0 % data', '8 % docs in cluster', '213B avg obj size on shard' ],
'Shard rs08': [ '0 % data', '8.6 % docs in cluster', '233B avg obj size on shard' ],
'Shard rs10': [ '0 % data', '7.4 % docs in cluster', '222B avg obj size on shard' ]
}
The only reason I see for such behavior is that reshardCollection command does some preliminary queries/aggregation involving sorting for further work, like counting documents to copy etc., and during this phase something sort memory limit gets exceeded due to a large number of documents or chunks in the collection.
Probably those sort operations need to be done with allowDiskUse option set to tru
- is related to
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- Closed
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