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Troubleshoot Live Migration (Pull)

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  • Common Live Migration (Pull) Validation Errors
  • Common Post-Validation Errors

Before the live migration (pull) process begins, Atlas performs a validation check to ensure that all the necessary form fields and parameters are functional and correct. If any parameters are invalid, Atlas returns an error and live migration does not proceed.

This section describes common live migration (pull) validation errors and provides suggestions for what to check if you encounter them.

Error
Remediation
Could not reach specified source
  • Ensure that you added the correct subnet ranges to the IP access list on the source cluster. You can find the four required subnet ranges in the live migration modal window.

  • Confirm that the hostname that you specified resolves to a public IP address. At a command prompt, use one of the following commands:

    nslookup <hostname>
    ping <hostname>
  • Ensure that you are not using a VPC Peering Connection, which is not compatible with pull live migration. If a VPC Peering Connection is your only option, use mongomirror instead.

Could not resolve hostname
No IP address was found for the given hostname. Confirm that the given hostname is correct and publicly accessible.
Invalid SSL options provided

If you are using SSL:

  • Confirm that your SSL certificate is complete and correctly copied to the live migration (pull) modal window.

  • Confirm that the Is SSL enabled? toggle switch is in the Yes position.

If you are not using SSL:

  • Check your connection string and confirm that the ssl query parameter is not present. If --ssl is part of your connection string, your cluster requires an SSL connection.

  • Confirm that the Is SSL enabled? toggle switch is in the No position.

The username or password is not correct

Confirm your credentials in mongosh with the following commands:

use admin
db.getUser("<username>");

If the issue persists, update the MongoDB user's password.

User not authorized to execute command
To run the live migration (pull) process, the MongoDB user must have sufficient system privileges. To learn more, see Source Cluster Security.
Disk storage info unavailable
To run the live migration (pull) process, the MongoDB user must have permissions on the source cluster's MongoBD instance. To learn more, see Source Cluster Security.
Source disk usage is too large for destination
Different Atlas service tiers have different amounts of disk space available. Ensure that your Atlas cluster has enough disk space for all the data on your source cluster. To learn more about cluster sizings, see Create a New Cluster.
Source appears to be a standalone
Your source deployment must be a MongoDB replica set. If your source deployment is currently a standalone node, convert it to a single-node replica set before running live migration (pull).
Unable to process the provided CA file
Confirm that your CA file is complete and correctly pasted into the live migration (pull) modal window.
Error
Remediation
Could not retrieve the latest oplog entry from the source: not found
Could not determine if --host is a replica set: error connecting to db server: no reachable servers
  • Ensure that you added every IP address the live migration (pull) service requires to the IP access list for your source cluster.

  • Confirm that the IP address or DNS hostname you provided resolves to an IP address that is publicly accessible.

Error applying oplog entries during initial sync: renameCollection command encountered during initial sync. Please restart mongomirror.

Renaming a collection on the source cluster during live migration (pull) may trigger this error.

  • Ensure that no users or applications rename any collections while the live migration (pull) is taking place.

  • Aggregation operations which use $out may trigger this error. Ensure that no $out operations occur during the live migration (pull) procedure.

Unsupported index error
Certain types and configurations of indexes which were allowable in earlier versions of MongoDB are no longer supported in more recent versions. Check the release notes for the MongoDB version on your destination cluster for possible conflicts. If necessary, drop any indexes which cause errors and rebuild them after the live migration process is complete.
Error while tailing the oplog on the source: Checkpoint not available in oplog

Live migration (pull) uses the source oplog to sync operations which occur on the source cluster during the pull live migration procedure. If the source cluster oplog size is too small, it might not be able to record all the operations that occur on the source cluster during the sync, and live migration (pull) falls too far behind to catch up.

If you see this error:

  • Check the size of the source cluster oplog using the rs.printReplicationInfo() command. The server that is hosting mongomirror must have enough available disk space to contain the oplog data generated during the migration process.

  • If required, increase the size of the source oplog to support a replication window that is long enough to complete the live migration procedure.

  • If the error occurs when running mongomirror directly, restart mongomirror using --oplogPath to buffer oplog data to disk during the migration.

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