Exception caught on transport layer thread= – 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 analyzes 2 JSON files to detect many errors.

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This guide will help you check for common problems that cause the log ” Exception caught on transport layer thread= ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugins.

Log Context

Log “exception caught on transport layer [thread={}]” classname is NioGroupFactory.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

             return new WrappedNioGroup(refCountedGroup);

    private void onException(Exception exception) {
        logger.warn(new ParameterizedMessage("exception caught on transport layer [thread={}]"; Thread.currentThread().getName());

    private static class RefCountedNioGroup extends AbstractRefCounted implements NioGroup {


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