Elasticsearch ConcurrentSnapshotExecutionException: Concurrent snapshot execution - Common Causes & Fixes

Brief Explanation

The ConcurrentSnapshotExecutionException error occurs in Elasticsearch when there's an attempt to initiate a new snapshot while another snapshot operation is already in progress for the same repository.

Impact

This error can significantly impact backup and disaster recovery processes, potentially leading to:

• Incomplete or failed backups
• Increased downtime during restore operations
• Inconsistent snapshot states

Common Causes

1. Multiple snapshot requests initiated simultaneously
2. Long-running snapshot operations overlapping with new requests
3. Automated snapshot schedules conflicting with manual snapshot attempts
4. Misconfigured snapshot policies or scripts

Troubleshooting and Resolution Steps

1. Check current snapshot status:

   GET _snapshot/_status
   

2. Wait for any ongoing snapshots to complete before initiating a new one.

3. Review and adjust snapshot scheduling to prevent overlaps:

   • Increase the time between scheduled snapshots
   • Implement proper locking mechanisms in scripts or applications initiating snapshots

4. Use the wait_for_completion parameter when initiating snapshots to ensure sequential execution:

   PUT _snapshot/my_repository/my_snapshot?wait_for_completion=true
   

5. Monitor snapshot durations and adjust schedules accordingly to prevent conflicts.

6. Implement error handling in your applications to catch and properly manage this exception.

Best Practices

• Implement a centralized snapshot management system to coordinate snapshot operations across your cluster.
• Use unique names for each snapshot to avoid conflicts.
• Regularly clean up old snapshots to reduce repository size and potential conflicts.
• Consider using Elasticsearch's Snapshot Lifecycle Management (SLM) for automated, policy-driven snapshot scheduling.

Frequently Asked Questions

Q: Can I run multiple snapshots simultaneously in Elasticsearch?
A: Elasticsearch does not support concurrent snapshots for the same repository. You must wait for one snapshot to complete before starting another.

Q: How can I check if a snapshot is currently in progress?
A: Use the GET _snapshot/_status API call to check the status of all ongoing snapshot operations.

Q: What happens if I force-stop a running snapshot?
A: Force-stopping a snapshot can lead to incomplete backups and potential data inconsistencies. It's generally not recommended unless absolutely necessary.

Q: Can I snapshot different indices concurrently?
A: While you can't run concurrent snapshots in the same repository, you can snapshot different indices to different repositories simultaneously.

Q: How can I optimize snapshot performance to reduce the chance of conflicts?
A: Optimize snapshot performance by using source-only snapshots, excluding unnecessary data, and scheduling snapshots during low-traffic periods.