Log Now throttling indexing: numMergesInFlight=; maxNumMerges= – How To Solve Related Issues

Log Now throttling indexing: numMergesInFlight=; maxNumMerges= – How To Solve Related Issues

Opster Team

Jan-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you try running the Elasticsearch Error Check-Up  which can resolve issues causing many log errors (free and no installation required)


This guide will help you check for common problems that cause the log “Now throttling indexing: numMergesInFlight=; maxNumMerges=” 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.

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 discover the cause of many errors and provides suitable actionable recommendations. 

Log Context

Log”Now throttling indexing: numMergesInFlight={}; maxNumMerges={}” classname is InternalEngine.java
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

        public synchronized void beforeMerge(OnGoingMerge merge) {
            int maxNumMerges = mergeScheduler.getMaxMergeCount();
            if (numMergesInFlight.incrementAndGet() > maxNumMerges) {
                if (isThrottling.getAndSet(true) == false) {
                    logger.info("now throttling indexing: numMergesInFlight={}; maxNumMerges={}"; numMergesInFlight; maxNumMerges);


Related issues to this log

We have gathered selected Q&A from the community and issues from Github, that can help fix related issues please review the following for further information :

1 How to prevent Elasticsearch from index throttling? -views 7.98 K ,score 5

Figure out Indexing error in elasticsearch? -views   0.28 K,score 5


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