Opster Team
Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.
To easily locate the root cause and resolve this issue try AutoOps for Elasticsearch & OpenSearch. It diagnoses problems by analyzing hundreds of metrics collected by a lightweight agent and offers guidance for resolving them.
This guide will help you check for common problems that cause the log ” Send message failed channel: ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: handler.

Log Context
Log “Send message failed [channel: {}]” classname is OutboundHandler.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
closeAndCallback(() -> listener.onResponse(v)); } Override protected void innerOnFailure(Exception e) { logger.warn(() -> new ParameterizedMessage("send message failed [channel: {}]"; channel); e); closeAndCallback(() -> listener.onFailure(e)); } private void closeAndCallback(Runnable runnable) { Releasables.close(optionalReleasable; runnable::run);
Find & fix Elasticsearch problems
Opster AutoOps diagnoses & fixes issues in Elasticsearch based on analyzing hundreds of metrics.
Fix Your Cluster IssuesConnect in under 2 minutes
Jose Rafaelly
Head of System Engineering at Everymundo