The cluster.routing.rebalance.enable setting in Elasticsearch controls whether shard rebalancing is allowed in the cluster. This setting affects how Elasticsearch distributes shards across nodes to maintain an even distribution of data and workload.
- Default value:
all - Possible values:
all,primaries,replicas,none - Recommendations: The default value is suitable for most use cases. However, you may want to adjust this setting during specific operations or in certain cluster states.
This setting determines which types of shards can be rebalanced:
all: Both primary and replica shards can be rebalancedprimaries: Only primary shards can be rebalancedreplicas: Only replica shards can be rebalancednone: No shards will be rebalanced
Example
To disable all shard rebalancing temporarily, apply this dynamic setting:
PUT /_cluster/settings
{
"persistent": {
"cluster.routing.rebalance.enable": "none"
}
}
You might want to change this setting during maintenance operations, large bulk indexing jobs, or when you need to prevent any shard movements temporarily. The effect of this change is that Elasticsearch will not attempt to rebalance shards across nodes until you re-enable it.
Common Issues and Misuses
- Leaving rebalancing disabled for extended periods can lead to uneven data distribution and suboptimal cluster performance.
- Frequent changes to this setting can cause unnecessary shard movements and impact cluster stability.
Do's and Don'ts
- Do use this setting to temporarily pause rebalancing during maintenance or large data operations.
- Do monitor cluster health and shard distribution after changing this setting.
- Don't leave rebalancing disabled for long periods in a production environment.
- Don't frequently toggle this setting as it can lead to unnecessary shard movements.
Frequently Asked Questions
Q: How does disabling rebalancing affect cluster performance?
A: Disabling rebalancing can lead to uneven shard distribution over time, potentially causing some nodes to be overloaded while others are underutilized. This can result in suboptimal query performance and resource utilization.
Q: Can I change this setting on a per-index basis?
A: No, this is a cluster-wide setting and applies to all indices in the cluster.
Q: How long does it take for changes to this setting to take effect?
A: Changes to this setting take effect immediately, but existing rebalancing operations may complete before the new setting is fully enforced.
Q: Will disabling rebalancing affect new shard allocations?
A: No, this setting only affects the rebalancing of existing shards. New shards will still be allocated according to the cluster's allocation rules.
Q: How can I monitor the impact of changing this setting?
A: You can use Elasticsearch's cluster health API and monitoring tools to observe shard distribution, node load, and overall cluster performance before and after changing this setting.
