Cluster Manager Task Queue Buildup

warning

scalingUpdated Feb 18, 2026

ClusterManager_PendingQueueSize growth indicates the cluster manager node is overwhelmed with cluster state update tasks (index creation, mapping updates, shard allocation), potentially leading to slow cluster state propagation and operational delays.

Sources

Logs - OpenSearch Documentationopensearch.org

Metrics referencedocs.opensearch.org

Technologies:

OpenSearchSymptoms of this issue are visible in OpenSearch metrics and logs

How to detect:

Monitor ClusterManager_PendingQueueSize trending upward. Correlate with Master_Task_Queue_Time and Master_Task_Run_Time to identify slow-executing tasks. Check Master_ThrottledPendingTasksCount for throttling behavior.

Recommended action:

Enable org.opensearch.cluster logging at DEBUG level to identify specific slow tasks. Reduce cluster state update frequency (batch index creations, reduce mapping updates). Consider dedicated cluster manager nodes or upgrade cluster manager node resources. Investigate ClusterApplierService_Latency and PublishClusterState_Latency for bottlenecks.