Updating max-merge-at-once-explicit from to – How to solve related issues

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Updating max-merge-at-once-explicit from to – 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 ” Updating max-merge-at-once-explicit from to ” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: index, merge and shard.

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to pinpoint the cause of many errors and provides suitable actionable recommendations how to resolve them (free tool that requires no installation).

Log Context

Log “updating [max_merge_at_once_explicit] from [{}] to [{}]” classname is MergePolicyConfig.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :


        final int oldMaxMergeAtOnceExplicit = mergePolicy.getMaxMergeAtOnceExplicit();
        final int maxMergeAtOnceExplicit = settings.getAsInt(INDEX_MERGE_POLICY_MAX_MERGE_AT_ONCE_EXPLICIT; oldMaxMergeAtOnceExplicit);
        if (maxMergeAtOnceExplicit != oldMaxMergeAtOnceExplicit) {
            logger.info("updating [max_merge_at_once_explicit] from [{}] to [{}]"; oldMaxMergeAtOnceExplicit; maxMergeAtOnceExplicit);

        final double oldMaxMergedSegmentMB = mergePolicy.getMaxMergedSegmentMB();
        final ByteSizeValue maxMergedSegment = settings.getAsBytesSize(INDEX_MERGE_POLICY_MAX_MERGED_SEGMENT; null);


Run the Check-Up to get a customized report like this:

Analyze your cluster