Key invalid host host – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.5-8.9

Briefly, this error occurs when Elasticsearch is unable to recognize the host specified in the configuration. This could be due to a typo, incorrect IP address, or a non-resolvable hostname. To resolve this issue, you can verify the host’s correctness in the Elasticsearch configuration file. Ensure that the host is reachable from the machine where Elasticsearch is running. If you’re using a hostname, try using the IP address instead. Also, check your network settings and firewall rules to ensure they’re not blocking the connection.

This guide will help you check for common problems that cause the log ” [” + key + “] invalid host: [” + host + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.

Log Context

Log “[” + key + “] invalid host: [” + host + “]” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 final HttpHost httpHost;  try {
 httpHost = HttpHostBuilder.builder(host).build();
 } catch (final IllegalArgumentException e) {
 throw new SettingsException("[" + key + "] invalid host: [" + host + "]"; e);
 }  if (TYPE.equals(httpHost.getSchemeName())) {
 httpHostFound = true;
 } else {


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