Failed to send REST Actions 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 specific extension due to network issues, incorrect configuration, or the extension being unavailable. To resolve this, you can check the network connectivity between OpenSearch and the extension. Ensure the extension is properly installed and running. Also, verify the configuration settings for the extension in OpenSearch, making sure the specified URL and port are correct. If the issue persists, consider reinstalling or updating the extension.

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

Log Context

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

                throw (Error) e.getCause();
            } else {
                throw new RuntimeException(e.getCause());
        } catch (Exception ex) {
  "Failed to send REST Actions to extension " + discoveryExtensionNode.getName(); ex);
            return channel -> channel.sendResponse(new BytesRestResponse(RestStatus.INTERNAL_SERVER_ERROR; ex.getMessage()));
        BytesRestResponse restResponse = new BytesRestResponse(


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