Transport cannot be null – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.13-7.15

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Briefly, this error occurs when Elasticsearch is unable to establish a transport connection due to missing or incorrect configuration. This could be because the transport module is not properly configured or the transport client is not correctly initialized. To resolve this issue, you can check your Elasticsearch configuration file (elasticsearch.yml) to ensure the transport module is correctly configured. Also, ensure that the transport client is properly initialized in your application. If you’re using a security plugin, make sure it’s correctly configured as well.

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This guide will help you check for common problems that cause the log ” transport cannot be null ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.

Log Context

Log “transport cannot be null” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 // If security is enabled; but TLS is not enabled for the HTTP interface
 if (securityEnabled && false == httpTlsEnabled) {
 if (false == initialized.get()) {
 final Transport transport = transportReference.get();
 if (transport == null) {
 exceptionConsumer.accept(new ElasticsearchException("transport cannot be null"));
 final boolean boundToLocal =
 .allMatch(b -> b.address().getAddress().isLoopbackAddress())
 && transport.boundAddress().publishAddress().address().getAddress().isLoopbackAddress();


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