The indices.recovery.max_concurrent_snapshot_file_downloads setting in Elasticsearch controls the maximum number of concurrent file downloads allowed during snapshot recovery operations. This setting helps manage the resource utilization and network bandwidth consumption during the recovery process.
- Default value: 5
- Possible values: Any positive integer
- Recommendation: The default value is suitable for most scenarios, but it can be adjusted based on available resources and recovery performance requirements.
This setting limits the number of files that can be downloaded simultaneously from a snapshot repository during recovery. It helps prevent overwhelming the network or the snapshot repository with too many concurrent requests.
Example
To change the indices.recovery.max_concurrent_snapshot_file_downloads setting using the cluster settings API:
PUT _cluster/settings
{
"persistent": {
"indices.recovery.max_concurrent_snapshot_file_downloads": 10
}
}
Increasing this value can potentially speed up snapshot recovery operations by allowing more files to be downloaded in parallel. However, this should be done cautiously, considering the available network bandwidth and the capabilities of the snapshot repository.
Common Issues and Misuses
- Setting the value too high can lead to network congestion or overwhelm the snapshot repository.
- Setting the value too low may unnecessarily slow down recovery operations.
- Failing to consider the impact on other ongoing cluster operations when adjusting this setting.
Do's and Don'ts
Do's:
- Monitor recovery performance and adjust the setting if needed.
- Consider the available network bandwidth and snapshot repository capabilities when changing the value.
- Test changes in a non-production environment before applying to production.
Don'ts:
- Don't set an excessively high value without considering the potential impact on network and repository resources.
- Avoid frequent changes to this setting without proper monitoring and testing.
- Don't ignore other recovery-related settings when optimizing snapshot recovery performance.
Frequently Asked Questions
Q: How does this setting affect snapshot recovery time?
A: This setting can influence recovery time by controlling the parallelism of file downloads. A higher value may reduce recovery time but could also increase resource consumption.
Q: Can changing this setting impact ongoing cluster operations?
A: Yes, increasing this value can lead to higher network and I/O utilization, potentially affecting other cluster operations.
Q: Is it safe to increase this value on a production cluster?
A: While it's generally safe, it's recommended to test changes in a non-production environment first and monitor the impact closely when applying to production.
Q: How does this setting interact with other recovery-related settings?
A: This setting works in conjunction with other recovery settings. It's important to consider the overall recovery configuration, including settings like indices.recovery.max_bytes_per_sec, for optimal performance.
Q: Can this setting be changed dynamically?
A: Yes, this setting can be updated dynamically using the cluster settings API without requiring a cluster restart.
