Engine failed; but cant find index shard. failure reason: – 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 can resolve issues that cause many errors.

This guide will help you check for common problems that cause the log ” Engine failed; but cant find index shard. failure reason: ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: cluster and indices.

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up to analyze Elasticsearch configuration and help resolve this error.

Log Context

Log “[{}][{}] engine failed; but can’t find index shard. failure reason: [{}]” classname is IndicesClusterStateService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                 if (indexShard != null) {
                    shardRouting = indexShard.routingEntry();
            if (shardRouting == null) {
                logger.warn("[{}][{}] engine failed; but can't find index shard. failure reason: [{}]"; failure;
                        shardId.index().name(); shardId.id(); reason);
            final ShardRouting fShardRouting = shardRouting;
            threadPool.generic().execute(new Runnable() {


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