Updating max_merge_size from to – How to solve related issues

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Updating max_merge_size 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_size 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 and merge.

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_size from [{}] to [{}]” classname is LogByteSizeMergePolicyProvider.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :


            ByteSizeValue maxMergeSize = settings.getAsBytesSize(INDEX_MERGE_POLICY_MAX_MERGE_SIZE; LogByteSizeMergePolicyProvider.this.maxMergeSize);
            if (!maxMergeSize.equals(LogByteSizeMergePolicyProvider.this.maxMergeSize)) {
                logger.info("updating max_merge_size from [{}] to [{}]"; LogByteSizeMergePolicyProvider.this.maxMergeSize; maxMergeSize);
                LogByteSizeMergePolicyProvider.this.maxMergeSize = maxMergeSize;
                for (CustomLogByteSizeMergePolicy policy : policies) {


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

Analyze your cluster