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Restore a Replica Set from MongoDB Backups

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This procedure outlines the process for taking MongoDB data and restoring that data into a new replica set. Use this approach for seeding test deployments from production backups or as part of disaster recovery.

Important

You cannot restore a single data set to three new mongod instances and then create a replica set. If you copy the data set to each mongod instance and then create the replica set, MongoDB will force the secondaries to perform an initial sync. The procedures in this document describe the correct and efficient ways to deploy a restored replica set.

You can also use mongorestore to restore database files using data created with mongodump. See Back Up and Restore with MongoDB Tools for more information.

Restore Database into a Single Node Replica Set

1

Obtain backup MongoDB Database files.

The backup files may come from a file system snapshot. The MongoDB Cloud Manager produces MongoDB database files for stored snapshots and point in time snapshots. For Ops Manager, an on-premise solution available in MongoDB Enterprise Advanced, see also the Ops Manager Backup overview.

Considerations for Encrypted Storage Engines

For encrypted storage engines that use AES256-GCM encryption mode, AES256-GCM requires that every process use a unique counter block value with the key.

For encrypted storage engine configured with AES256-GCM cipher:

  • Restoring from Hot Backup

    Starting in 4.2, if you restore from files taken via “hot” backup (i.e. the mongod is running), MongoDB can detect “dirty” keys on startup and automatically rollover the database key to avoid IV (Initialization Vector) reuse.

  • Restoring from Cold Backup

    However, if you restore from files taken via “cold” backup (i.e. the mongod is not running), MongoDB cannot detect “dirty” keys on startup, and reuse of IV voids confidentiality and integrity guarantees.

    Starting in 4.2, to avoid the reuse of the keys after restoring from a cold filesystem snapshot, MongoDB adds a new command-line option --eseDatabaseKeyRollover. When started with the --eseDatabaseKeyRollover option, the mongod instance rolls over the database keys configured with AES256-GCM cipher and exits.

Tip

  • In general, if using filesystem based backups for MongoDB Enterprise 4.2+, use the “hot” backup feature, if possible.
  • For MongoDB Enterprise versions 4.0 and earlier, if you use AES256-GCM encryption mode, do not make copies of your data files or restore from filesystem snapshots (“hot” or “cold”).
2

Drop the local database if it exists in the backup.

If you are restoring from a filesystem backup (or any backup with the local database), drop the local database.

Start a standalone mongod using the data files from the backup as the data path.

copy 
mongod --dbpath /data/db

Drop the local database.

Connect mongo shell to the mongod instance and drop the local database.

copy 
use local
db.dropDatabase()

Shut down the standalone.

3

Start a new single-node replica set.

Start a mongod instance as a new single-node replica set. Specify the path to the backup data files with --dbpath option and the replica set name with the --replSet option. For config server replica set (CSRS), include the --configsvr option. Include any other options as appropriate for your deployment.

Note

Starting in MongoDB 3.6, if your replica set members are run on different hosts or if you wish remote clients to connect to your instance, you must specify the net.bindIp setting (or --bind_ip).

Warning

Before binding to a non-localhost (e.g. publicly accessible) IP address, ensure you have secured your cluster from unauthorized access. For a complete list of security recommendations, see Security Checklist. At minimum, consider enabling authentication and hardening network infrastructure.

copy 
mongod --dbpath /data/db --replSet <replName>

Note

New in version 3.6:

All MongoDB collections have UUIDs by default. When MongoDB restores collections, the restored collections retain their original UUIDs. When restoring a collection where no UUID was present, MongoDB generates a UUID for the restored collection.

For more information on collection UUIDs, see Collections.

4

Connect a mongo shell to the mongod instance.

From the same machine where one of the mongod is running (in this tutorial, mongodb0.example.net), start the mongo shell. To connect to the mongod listening to localhost on the default port of 27017, simply issue:

copy 
mongo

Depending on your path, you may need to specify the path to the mongo binary.

5

Initiate the new replica set.

Use rs.initiate() on one and only one member of the replica set:

copy 
rs.initiate( {
   _id : <replName>,
   members: [ { _id : 0, host : <host:port> } ]
})

MongoDB initiates a set that consists of the current member and that uses the default replica set configuration.

Add Members to the Replica Set

MongoDB provides two options for restoring secondary members of a replica set:

Note

If your database is large, initial sync can take a long time to complete. For large databases, it might be preferable to copy the database files onto each host.

Copy Database Files and Restart mongod Instance

Use the following sequence of operations to “seed” additional members of the replica set with the restored data by copying MongoDB data files directly.

1

Shut down the mongod instance that you restored.

Use --shutdown or db.shutdownServer() to ensure a clean shut down.

2

Copy the primary’s data directory to each secondary.

Copy the primary’s data directory into the dbPath of the other members of the replica set.

3

Start the mongod instance that you restored.

4

Add the secondaries to the replica set.

In a mongo shell connected to the primary, add the secondaries to the replica set using rs.add(). See Deploy a Replica Set for more information about deploying a replica set.

Update Secondaries using Initial Sync

Use the following sequence of operations to “seed” additional members of the replica set with the restored data using the default initial sync operation.

1

Empty the data directory for each prospective replica set member.

For example, if the replica set member has a storage.dbPath or --dbpath of /data/db, you must ensure that directory exists and is empty.

2

Start each replica set member.

3

Add each prospective member to the replica set.

Connect to the primary using the mongo shell and add each secondary to the replica set using rs.add().

When you add a member to the replica set, Initial Sync copies the data from the primary to the new member.

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