Failed to connect to – How to solve related issues

Opster Team

Jan-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.

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 ” Failed to connect to ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: cluster and node.

Log Context

Log “Failed to connect to {}” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                     public void onFailure(Exception e) {
                        // both errors and rejections are logged here. the service
                        // will try again after `cluster.nodes.reconnect_interval` on all nodes but the current master.
                        // On the master; node fault detection will remove these nodes from the cluster as their are not
                        // connected. Note that it is very rare that we end up here on the master.
                        logger.warn(() -> new ParameterizedMessage("failed to connect to {}"; node); e);

                    protected void doRun() {
                        try (Releasable ignored = nodeLocks.acquire(node)) {


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