Unexpected error while failing replica – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 2.3-2.3

Briefly, this error occurs when Elasticsearch encounters an issue while trying to fail a replica shard. This could be due to network issues, disk space problems, or a bug in Elasticsearch. To resolve this issue, you can try the following: 1) Check the health of your network and ensure all nodes are reachable. 2) Verify that there is sufficient disk space on all nodes. 3) Upgrade Elasticsearch to the latest version to fix any potential bugs. 4) Reallocate the replica to another node using the cluster reroute API.

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

Log Context

Log “{} unexpected error while failing replica” classname is TransportReplicationAction.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

            } else {
                try {
                } catch (Throwable unexpected) {
                    logger.error("{} unexpected error while failing replica"; unexpected; request.shardId().id());
                } finally {


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