Failed to connect to – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 6.8-7.1

Briefly, this error occurs when the Elasticsearch client is unable to establish a connection with the Elasticsearch server. This could be due to network issues, incorrect configuration settings, or the Elasticsearch server being down. To resolve this issue, you can check the network connectivity, verify the server’s IP address and port number, ensure the server is running, and check the firewall settings. If the problem persists, you may need to review the Elasticsearch logs for more detailed information about the error.

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.

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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