Unexpected failure while failing shard – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 6.8-8.2

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Briefly, this error occurs when Elasticsearch encounters an issue while trying to mark a shard as failed. This could be due to a network disruption, disk issues, or a bug in Elasticsearch. To resolve this issue, you can try the following: 1) Check the health of your network and disk. 2) Ensure that your Elasticsearch cluster has enough resources. 3) Upgrade Elasticsearch to the latest version to fix potential bugs. 4) If a specific shard consistently fails, consider reindexing the data.

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This guide will help you check for common problems that cause the log ” {} unexpected failure while failing shard [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: cluster, shard.

Log Context

Log “{} unexpected failure while failing shard [{}]” classname is ShardStateAction.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

            if (e instanceof NotMasterException) {
                logger.debug(() -> new ParameterizedMessage("{} no longer master while failing shard [{}]"; entry.shardId; entry));
            } else if (e instanceof FailedToCommitClusterStateException) {
                logger.debug(() -> new ParameterizedMessage("{} unexpected failure while failing shard [{}]"; entry.shardId; entry); e);
            } else {
                logger.error(() -> new ParameterizedMessage("{} unexpected failure while failing shard [{}]"; entry.shardId; entry); e);



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