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Resync Backup

Overview

When a backup becomes out of sync with the MongoDB deployment, Ops Manager produces a Backup requires resync alert. If you receive a Backup requires resync alert, you must resync the backup for the specified MongoDB instance.

The following scenarios trigger a Backup requires resync alert:

  • The Oplog has rolled over. This is by far the most common case for the Backup requires resync alert and occurs whenever the Backup Agent’s tailing cursor cannot keep up with the deployment’s oplog. This is similar to when a secondary falls too far behind the primary in a replica set. Without a resync, the Backups will not catch up.
  • Unsafe applyOps. This occurs when a document that Backup does not have a copy of is indicated.
  • Data corruption or other illegal instruction. This typically causes replication, and therefore the backup job, to break. When the daemon sees the broken job, it requests a resync.

During the resync, data is read from a secondary in each replica set and Ops Manager does not produce any new snapshots.

Note

For production deployments, you should resync all backups annually.

Considerations

To avoid the need for resyncs, ensure the Backup oplog does not fall behind the deployment’s oplog. This requires that:

  • adequate machine resources are provisioned for the agent, and that
  • you restart the Ops Manager agents in a timely manner following maintenance or other downtime.

To provide a buffer for maintenance and for occasional activity bursts, ensure that the oplog on the primary is large enough to contain at least 24 hours of activity. For more information on the Backup oplog, see the Backup FAQs.

Procedures

Use the appropriate procedure below for your deployment type, sharded cluster or replica set.

Resync a Sharded Cluster

1

Select the Backup tab and then select Sharded Cluster Status.

2

Select See Shards/Configs.

The column expands to display the shards and config servers.

3

Resync.

For the MongoDB instance to resync:

Click the resync link.

Accept the default selection in the Sync source drop-down list, and click the RESYNC button.

If prompted for a two-factor verification code, enter the code and click VERIFY. Then click the RESYNC button again.

Resync a Replica Set

1

Select the Backup tab and then select Replica Set Status.

2

In the replica set’s LAST SYNC column, select resync.

3

Select a Sync source and click the RESYNC button.

If prompted for a two-factor verification code, enter the code and click VERIFY. Then click the RESYNC button again.