Master processed stale shard-started event failing shard – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.17-8.9

Briefly, this error occurs when the Elasticsearch master node processes an outdated shard-started event. This could be due to network issues, node failures, or slow processing. To resolve this, you can try restarting the Elasticsearch cluster to refresh the state of the shards. If the issue persists, check for network connectivity issues or hardware failures. Additionally, consider increasing the node’s resources if it’s under heavy load, as this could be causing slow processing times.

This guide will help you check for common problems that cause the log ” master processed stale shard-started event; failing shard ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: shard, master, index.

Log Context

Log “master processed stale shard-started event; failing shard” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 // NB this can only happen on replicas - if it happened to a primary then we'd move to a new primary term and ignore the
 // stale shard-started message.
 assert newRouting.primary() == false
 : "primary routing is active; but local shard state isn't. routing: " + newRouting + "; local state: " + state;
 throw new IllegalIndexShardStateException(shardId; state; "master processed stale shard-started event; failing shard");
 }  persistMetadata(path; indexSettings; newRouting; currentRouting; logger);
 final CountDownLatch shardStateUpdated = new CountDownLatch(1);


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