Failed to connect to node – 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.

Briefly, this error occurs when Elasticsearch is unable to connect to a node in the cluster. Nodes are responsible for storing data and executing search queries, so this error can result in degraded performance or downtime. The cause of this error can be due to a network configuration issue, the affected node is unreachable or down, or a misconfiguration of Elasticsearch. To resolve this error, you can check the network configuration to ensure that the affected node is reachable, and verify that the affected node is running and that it has not encountered any issues. Additionally, you can increase the number of nodes in the cluster to increase the resilience of the cluster.

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. Take a self-guided product tour to see for yourself (no registration required).

This guide will help you check for common problems that cause the log ” Failed to connect to node ” 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 node [” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                try {
                } catch (Throwable e) {
                    // the fault detection will detect it as failed as well
                    logger.warn("failed to connect to node [" + node + "]"; e);

            // if we are the master; publish the new state to all nodes
            // we publish here before we send a notification to all the listeners; since if it fails


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