- Sharding >
- Sharded Cluster Administration >
- Clear
jumbo
Flag
Clear jumbo
Flag¶
On this page
If MongoDB cannot split a chunk that exceeds the specified chunk size, MongoDB labels the chunk as jumbo.
If the chunk size no longer exceeds the specified chunk size, MongoDB clears the jumbo
flag for the chunk
when the mongos
rewrites the chunk metadata.
In cases where you need to clear the flag manually, the following
procedures outline the steps to manually clear the jumbo
flag.
Procedures¶
Divisible Chunks¶
The preferred way to clear the jumbo
flag from a chunk is to
attempt to split the chunk. If the chunk is divisible, MongoDB removes
the flag upon successful split of the chunk.
Find the jumbo
Chunk.¶
Run sh.status(true)
to find the chunk labeled
jumbo
.
For example, the following output from sh.status(true) shows that
chunk with shard key range { "x" : 2 } -->> { "x" : 4 }
is
jumbo
.
Split the jumbo
Chunk.¶
Use either sh.splitAt()
or sh.splitFind()
to
split the jumbo
chunk.
MongoDB removes the jumbo
flag upon successful split of the
chunk.
Indivisible Chunks¶
In some instances, MongoDB cannot split the no-longer jumbo
chunk,
such as a chunk with a range of single shard key value, and the
preferred method to clear the flag is not applicable. In such cases,
you can clear the flag using the following steps.
- For MongoDB v4.0.15+
- For MongoDB 4.0.14 and earlier
Starting in 4.0.15, MongoDB provides the
clearJumboFlag
command to manually clear the
jumbo
flag.
Important
Only use this method if the preferred method is not applicable.
Find the jumbo
Chunk.¶
Run sh.status(true)
to find the chunk labeled
jumbo
.
For example, the following output from sh.status(true) shows that
chunk with shard key range { "x" : 2 } -->> { "x" : 3 }
is
jumbo
.
Run the clearJumboFlag
Command.¶
From the admin
database, run the clearJumboFlag
,
passing in the namespace of the sharded collection and either:
the bounds of the
jumbo
chunk:the find document with a shard key and value contained in the
jumbo
chunk:Note
If the collection uses a hashed shard key, do not use the
find
field withclearJumboFlag
. For hashed shard keys, use thebounds
field instead.
Important
Only use this method if the preferred method is not applicable.
Before modifying the config database, always back up the config database.
Stop the balancer.¶
Disable the cluster balancer process temporarily, following the steps outlined in Disable the Balancer.
Find the jumbo
Chunk.¶
Run sh.status(true)
to find the chunk labeled
jumbo
.
For example, the following output from sh.status(true) shows that
chunk with shard key range { "x" : 2 } -->> { "x" : 3 }
is
jumbo
.
Update chunks
collection.¶
In the chunks
collection of the config
database, unset the
jumbo
flag for the chunk. For example,
Clear the cached routing information.¶
After the jumbo flag has been cleared out from the chunks
collection, update the cluster routing metadata cache.
- Starting in MongoDB 4.0.6 (and 3.6.11),
You must flush the cache on the config server primary for the namespace. This notifies the balancer of the jumbo flag clearance.
Connect a
mongo
shell to the config server primary and runflushRouterConfig
for the collection:- In earlier versions (MongoDB 3.4-series, MongoDB 3.6.0-3.6.10, MongoDB 4.0.0-4.0.5),
- Step down the config server primary to clear the routing metadata cache from the config servers.
If you clear the jumbo
flag for a chunk that still exceeds the
chunk size, MongoDB will re-label the chunk as jumbo
when MongoDB
tries to move the chunk.