Failed to merge – 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 merge ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index and merge.

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 merge” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :


        protected void handleMergeException(final Directory dir; final Throwable exc) {
            logger.error("failed to merge"; exc);
            if (config().getMergeSchedulerConfig().isNotifyOnMergeFailure()) {
                engineConfig.getThreadPool().generic().execute(new AbstractRunnable() {
                    public void onFailure(Throwable t) {
                        logger.debug("merge failure action rejected"; t);


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