Updating cluster.routing.allocation.cluster-concurrent-rebalance from ; to – How to solve related issues

Opster Team

Feb-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.

Briefly, this error message is indicating that there is an issue with the cluster-concurrent-rebalance setting in the Elasticsearch cluster routing allocation. This setting controls the number of concurrent shard rebalances that can take place in the cluster at any given time. It appears that the value for this setting is missing or incorrect. To resolve this issue, you should check the current value of the cluster-concurrent-rebalance setting and update it to an appropriate value for your cluster.

To easily locate the root cause and resolve this issue try AutoOps for Elasticsearch & OpenSearch. It diagnoses problems by analyzing hundreds of metrics collected by a lightweight agent and offers guidance for resolving them.

This guide will help you check for common problems that cause the log ” Updating cluster.routing.allocation.cluster-concurrent-rebalance from ; to ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: allocation, cluster, rebalance and routing.

Log Context

Log “updating [cluster.routing.allocation.cluster_concurrent_rebalance] from [{}]; to [{}]” classname is ConcurrentRebalanceAllocationDecider.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

     class ApplySettings implements NodeSettingsService.Listener {
        public void onRefreshSettings(Settings settings) {
            int clusterConcurrentRebalance = settings.getAsInt(CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE; ConcurrentRebalanceAllocationDecider.this.clusterConcurrentRebalance);
            if (clusterConcurrentRebalance != ConcurrentRebalanceAllocationDecider.this.clusterConcurrentRebalance) {
                logger.info("updating [cluster.routing.allocation.cluster_concurrent_rebalance] from [{}]; to [{}]"; ConcurrentRebalanceAllocationDecider.this.clusterConcurrentRebalance; clusterConcurrentRebalance);
                ConcurrentRebalanceAllocationDecider.this.clusterConcurrentRebalance = clusterConcurrentRebalance;


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