The indices.recovery.max_concurrent_operations setting in Elasticsearch controls the maximum number of concurrent operations allowed during shard recovery processes. This setting plays a crucial role in managing the performance and resource utilization during index recovery operations.
- Default Value: 1
- Possible Values: Any positive integer
- Recommendation: The optimal value depends on your cluster's hardware capabilities and recovery requirements. Increasing this value can speed up recovery processes but may also increase system load.
This setting limits the number of concurrent file operations (such as file opens) that can occur during shard recovery. It helps prevent overwhelming the system with too many simultaneous operations, which could lead to performance degradation or system instability.
Example
To change the indices.recovery.max_concurrent_operations setting using the cluster settings API:
PUT _cluster/settings
{
"persistent": {
"indices.recovery.max_concurrent_operations": 4
}
}
In this example, we're increasing the concurrent operations to 4. This might be beneficial in scenarios where you have powerful hardware and want to speed up recovery processes. However, be cautious as setting this value too high could overload your system.
Common Issues and Misuses
- Setting the value too high can lead to excessive disk I/O and CPU usage, potentially slowing down other cluster operations.
- Setting the value too low might unnecessarily prolong recovery times, especially in clusters with high-performance hardware.
Do's and Don'ts
- Do monitor system resources (CPU, disk I/O, memory) when adjusting this setting.
- Do test changes in a non-production environment before applying to production.
- Don't set this value excessively high without considering your hardware limitations.
- Don't change this setting frequently; find a balanced value that works for your cluster.
Frequently Asked Questions
Q: How does this setting affect shard recovery speed?
A: Increasing indices.recovery.max_concurrent_operations can potentially speed up shard recovery by allowing more concurrent file operations. However, the actual impact depends on your hardware capabilities and other concurrent cluster activities.
Q: Can increasing this setting cause performance issues?
A: Yes, setting it too high can lead to excessive resource consumption, potentially slowing down other cluster operations or causing system instability.
Q: Is there a recommended value for this setting?
A: There's no one-size-fits-all recommendation. The optimal value depends on your specific hardware, cluster size, and recovery requirements. Start with the default and increase gradually while monitoring system performance.
Q: How does this setting interact with other recovery settings?
A: This setting works in conjunction with other recovery settings like indices.recovery.max_bytes_per_sec. While this setting controls concurrent operations, others might limit bandwidth or the number of concurrent recoveries. Consider all related settings for optimal recovery performance.
Q: Should I adjust this setting during ongoing recoveries?
A: It's generally not recommended to change this setting during active recoveries. Make adjustments when the cluster is stable and before initiating large-scale operations that might trigger recoveries.
