The index.routing.allocation.exclude._ip setting in Elasticsearch is used to control shard allocation by excluding specific IP addresses. This setting allows you to prevent shards from being allocated to nodes with certain IP addresses, providing fine-grained control over data distribution across your cluster.
- Default value: Not set (empty)
- Possible values: Comma-separated list of IP addresses or IP ranges
- Recommendations: Use sparingly and in conjunction with other allocation settings for balanced cluster management
This setting is part of the index-level shard allocation settings. When specified, Elasticsearch will avoid allocating shards of the index to nodes with IP addresses matching the provided list. This can be useful for various scenarios, such as isolating certain nodes for specific workloads or implementing rudimentary rack awareness.
Example
To exclude shards from being allocated to nodes with IP addresses 10.0.0.1 and 10.0.0.2:
PUT /my-index/_settings
{
"index.routing.allocation.exclude._ip": "10.0.0.1,10.0.0.2"
}
You might want to change this setting if you need to perform maintenance on specific nodes or if you want to ensure that certain high-traffic indices are not allocated to nodes with limited resources. The effect of this change is that Elasticsearch will attempt to move existing shards from the excluded IP addresses and prevent new shard allocations to those addresses.
Common Issues and Misuses
- Over-exclusion: Excluding too many IP addresses can lead to unbalanced shard distribution or allocation failures.
- Forgetting to reset: After maintenance or temporary exclusions, users sometimes forget to remove the exclusion, leading to long-term imbalances.
- Conflicts with other allocation settings: This setting may conflict with include or require rules, potentially resulting in allocation problems.
Do's and Don'ts
Do's:
- Use this setting in combination with other allocation settings for comprehensive control
- Regularly review and update exclusion lists to ensure they remain relevant
- Consider using more advanced features like awareness attributes for data center or rack-based allocation
Don'ts:
- Don't exclude all available nodes for an index, as this will prevent shard allocation entirely
- Avoid using this setting as a primary means of controlling allocation; consider it a fine-tuning tool
- Don't set this at the cluster level unless absolutely necessary; index-level settings provide more flexibility
Frequently Asked Questions
Q: Can I use wildcards or CIDR notation in the IP addresses?
A: Yes, you can use IP ranges in CIDR notation (e.g., 192.168.0.0/24) or wildcards (e.g., 192.168.0.*) to exclude multiple IP addresses.
Q: What happens if all available nodes are excluded for an index?
A: If all available nodes are excluded, the index's shards will remain unassigned, potentially impacting the availability and performance of your cluster.
Q: How does this setting interact with index.routing.allocation.include._ip?
A: The exclude setting takes precedence over include. If a node's IP is in both lists, it will be excluded from shard allocation for that index.
Q: Can I use this setting to implement rack awareness?
A: While it's possible to use IP-based exclusion for basic rack awareness, it's generally better to use the built-in awareness attributes for more robust and maintainable rack-aware shard allocation.
Q: How quickly does Elasticsearch respond to changes in this setting?
A: Elasticsearch typically responds to allocation setting changes quickly, but the actual reallocation of shards may take some time depending on the size of the shards and the current cluster state.
