Could not register Transport Action – 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 fails to register a transport action due to a conflict, such as duplicate action names or issues with the transport service. To resolve this, ensure that all transport actions have unique names and are correctly configured. If the problem persists, check the health of your transport service and restart it if necessary. Also, consider updating OpenSearch to the latest version as this could be a bug that has been fixed in newer versions.

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This guide will help you check for common problems that cause the log ” Could not register Transport Action: ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: .

Log Context

Log “Could not register Transport Action:” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

        try {
            for (String action : transportActionsRequest.getTransportActions()) {
                registerAction(action; transportActionsRequest.getUniqueId());
        } catch (Exception e) {
            logger.error("Could not register Transport Action: " + e.getMessage());
            return new AcknowledgedResponse(false);
        return new AcknowledgedResponse(true);


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