Restore a Self-Managed Sharded Cluster from Database Dumps

Stop the balancer.

To prevent chunk migrations from disrupting the restore, connect to mongos and stop the balancer:

sh.stopBalancer()

To verify that you stopped the balancer, run:

use config
while( sh.isBalancerRunning().mode != "off" ) {
   print( "Waiting for Balancer to stop..." );
   sleep( 1000 );
}

Pre-shard collections on the destination cluster.

For each sharded collection in the source cluster, create the collection on the destination cluster and shard it using the same shard key before restoring data.

To find the shard key for each collection, query the live source cluster:

use config
db.collections.find()

Alternatively, you can use bsondump to inspect the config/collections.bson file from your dump directory:

bsondump /path/to/dump/config/collections.bson

{
  "_id": "<database>.<collection>",
  ...
  "key": { "<shardKeyField>": "<key>" },
  ...
}

For each sharded collection, shard the collection on the destination cluster using the same shard key:

sh.shardCollection(
   "<database-name>.<collection-name>",
   { <shardKeyField>: <key> }
)

Restore the cluster.

Use mongorestore to connect to mongos and restore the cluster. Exclude the config database to preserve the destination cluster's existing configuration:

mongorestore \
   --host <host> \
   --port 27017 \
   --username <username> \
   --password "<password>" \
   --authenticationDatabase admin \
   --nsExclude='config.*' \
   /path/to/backup

Restart the balancer.

After the restore completes, restart the balancer:

sh.startBalancer()

To confirm that the balancer is running:

sh.isBalancerRunning().mode

full

Validate cluster accessibility.

Connect to mongos and run sh.status() to check the overall cluster status:

sh.status()

To confirm that all shards are accessible and communicating, insert a test document into a temporary collection:

db.testRestore.insertOne({ test: 1 })

Then connect to each shard primary and run db.collection.find() to confirm that the document is present:

db.testRestore.find()