No longer master while failing shard – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-1.3

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Briefly, this error occurs when a node that was previously the master is no longer the master, and it tries to fail a shard. This could be due to network issues, heavy load, or configuration problems causing the cluster state to change. To resolve this, you can try the following: 1) Check and improve your network connectivity, 2) Balance the load across nodes, 3) Review and correct your cluster configuration, and 4) Increase the master node election timeout setting.

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This guide will help you check for common problems that cause the log ” {} no longer master while failing shard [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: master, shard, cluster.

Log Context

Log “{} no longer master while failing shard [{}]” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :


                    public void onNoLongerMaster(String source) {
                        logger.error("{} no longer master while failing shard [{}]"; request.shardId; request);
                        try {
                            channel.sendResponse(new NotMasterException(source));
                        } catch (Exception channelException) {
                                () -> new ParameterizedMessage(


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