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

     class ApplySettings implements IndexSettingsService.Listener {
        public void onRefreshSettings(Settings settings) {
            int maxThreadCount = settings.getAsInt("index.merge.scheduler.max_thread_count"; ConcurrentMergeSchedulerProvider.this.maxThreadCount);
            if (maxThreadCount != ConcurrentMergeSchedulerProvider.this.maxThreadCount) {
                logger.info("updating [max_thread_count] from [{}] to [{}]"; ConcurrentMergeSchedulerProvider.this.maxThreadCount; maxThreadCount);
                ConcurrentMergeSchedulerProvider.this.maxThreadCount = maxThreadCount;
                for (CustomConcurrentMergeScheduler scheduler : schedulers) {
                    scheduler.setMaxMergesAndThreads(ConcurrentMergeSchedulerProvider.this.maxMergeCount; maxThreadCount);


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