Elasticsearch FailedToCommitClusterStateException: Failed to commit cluster state

Brief Explanation

The FailedToCommitClusterStateException occurs when Elasticsearch is unable to commit changes to the cluster state. This error indicates that there's a problem with the cluster's ability to update and synchronize its internal state across nodes.

Common Causes

Network issues between cluster nodes
Disk space problems on one or more nodes
Node failures or unresponsive nodes
Misconfiguration of cluster settings
High system load or resource constraints

Troubleshooting and Resolution Steps

Check cluster health:
```
GET _cluster/health
```
Verify node status:
```
GET _cat/nodes?v
```
Inspect cluster state:
```
GET _cluster/state
```
Review Elasticsearch logs for specific error messages.
Check disk space on all nodes:
```
GET _cat/allocation?v
```
Ensure all nodes can communicate with each other by checking network connectivity.
Verify that all nodes have sufficient resources (CPU, memory, disk I/O).
Restart problematic nodes if identified.
If the issue persists, consider rolling restart of the entire cluster.
Update Elasticsearch to the latest patch version within your major version.

Additional Information and Best Practices

Regularly monitor cluster health and performance metrics.
Implement proper capacity planning to avoid resource constraints.
Use shard allocation awareness to improve cluster stability.
Keep Elasticsearch and JVM versions up to date.
Configure appropriate timeouts for cluster state updates.

Frequently Asked Questions

Q1: Can this error cause data loss?

A1: Generally, this error doesn't cause data loss as it prevents changes from being committed. However, it may lead to temporary unavailability of some cluster operations.

Q2: How does this error affect cluster operations?

A2: It can prevent new indices from being created, shard allocations from changing, and other cluster-wide operations from completing.

Q3: Is this error related to the split-brain problem?

A3: While not directly related, both issues can stem from network problems or node communication issues. Proper configuration of discovery settings can help prevent both.

Q4: How can I prevent this error from occurring?

A4: Regular maintenance, proper resource allocation, network stability, and keeping your Elasticsearch version updated can help prevent this error.

Q5: Does increasing the `cluster.publish.timeout` setting help?

A5: Increasing this timeout can help in some cases where the cluster is just slow to respond, but it's not a solution for underlying issues causing the commit failures.