Failed to start shard – 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 ” Failed to start shard ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: cluster, indices and shard.

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 “[{}][{}] failed to start shard” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

             handleRecoveryFailure(indexService; indexMetaData; shardRouting; sendShardFailure; e);

    private void handleRecoveryFailure(IndexService indexService; IndexMetaData indexMetaData; ShardRouting shardRouting; boolean sendShardFailure; Throwable failure) {
        logger.warn("[{}][{}] failed to start shard"; failure; indexService.index().name(); shardRouting.shardId().id());
        synchronized (mutex) {
            if (indexService.hasShard(shardRouting.shardId().id())) {
                try {
                    indexService.removeShard(shardRouting.shardId().id(); "recovery failure [" + ExceptionsHelper.detailedMessage(failure) + "]");
                } catch (IndexShardMissingException e) {


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