The "TranslogCorruptedException: Translog corruption detected" error in Elasticsearch indicates that the translog, which records all operations that should be applied to the index, has become corrupted. This is a serious error that can affect data integrity and cluster stability.
Impact
This error has significant impact:
- Data loss or inconsistency: Some operations may not be properly recorded or replayed.
- Index unavailability: The affected index may become unavailable or read-only.
- Cluster instability: In severe cases, it might affect overall cluster health.
Common Causes
- Sudden node shutdown or crash
- Disk failures or I/O errors
- File system corruption
- Insufficient disk space
- Hardware issues
Troubleshooting and Resolution Steps
Check Elasticsearch logs for detailed error messages and affected indices.
Verify disk space and file system integrity on the affected node.
If possible, try to recover the index:
POST /_cluster/reroute?retry_failed=trueIf recovery fails, you may need to delete the corrupted translog:
DELETE /<index>Note: This will result in data loss for any uncommitted operations.
If the issue persists, consider restoring from a snapshot if available.
Restart the Elasticsearch node after addressing any underlying hardware or disk issues.
Monitor the cluster health and logs to ensure the issue is resolved.
Best Practices
- Regularly backup your Elasticsearch data using snapshots.
- Implement proper monitoring for disk space and I/O performance.
- Use high-quality, reliable hardware for production Elasticsearch clusters.
- Ensure graceful shutdowns of Elasticsearch nodes when possible.
- Regularly check and maintain file system health on all nodes.
Frequently Asked Questions
Q: Can I prevent translog corruption?
A: While you can't completely prevent it, you can minimize the risk by using reliable hardware, ensuring proper shutdown procedures, and maintaining adequate disk space and health.
Q: How often should I take snapshots to mitigate potential data loss from translog corruption?
A: The frequency depends on your data change rate and recovery point objective (RPO). For many use cases, daily snapshots are sufficient, but critical applications might require more frequent backups.
Q: Will increasing the translog flush interval help prevent corruption?
A: Increasing the flush interval can reduce I/O operations but won't necessarily prevent corruption. It's more important to address underlying causes like hardware reliability and proper shutdown procedures.
Q: Can translog corruption spread to other nodes or indices?
A: Typically, translog corruption is isolated to a specific shard on a specific node. However, if left unaddressed, it could potentially impact cluster stability or lead to data inconsistencies across replicas.
Q: After resolving a translog corruption, how can I verify the integrity of my data?
A: You can use Elasticsearch's _cat/indices API to check the health and document count of your indices. For more thorough verification, consider running a consistency check by reindexing the data and comparing document counts.
