Failed to send transport action to extension – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 2.5-2.9

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Briefly, this error occurs when OpenSearch is unable to communicate with a plugin or extension due to network issues, misconfiguration, or the extension being unavailable. To resolve this, ensure the extension is properly installed and configured. Check the network connectivity between OpenSearch and the extension. If the extension is running on a different node, ensure that the node is up and running. Also, check the OpenSearch logs for more detailed error messages that can provide additional clues to the problem.

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This guide will help you check for common problems that cause the log ” Failed to send transport action to extension ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: .

Log Context

Log “Failed to send transport action to extension” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                new ExtensionHandleTransportRequest(request.getAction(); request.getRequestBytes());
        } catch (Exception e) {
  "Failed to send transport action to extension " + extension.getName(); e);
        try {
            inProgressFuture.orTimeout(ExtensionsManager.EXTENSION_REQUEST_WAIT_TIMEOUT; TimeUnit.SECONDS).join();
        } catch (CompletionException e) {
            if (e.getCause() instanceof TimeoutException) {


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