OnIndexModule index – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 2.5-2.7

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Briefly, this error occurs when there’s an issue with the index module in OpenSearch. The index module could be misconfigured, missing, or incompatible with the current version of OpenSearch. To resolve this issue, you can try the following: 1) Check the configuration of the index module and correct any errors. 2) If the index module is missing, reinstall it. 3) If the index module is incompatible with the current version of OpenSearch, update the module or downgrade OpenSearch to a compatible version.

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

Log Context

Log “onIndexModule index:” classname is ExtensionsManager.java.
We extracted the following from OpenSearch source code for those seeking an in-depth context :

            onIndexModule(indexModule; extensionNode);

    private void onIndexModule(IndexModule indexModule; DiscoveryNode extensionNode) throws UnknownHostException {
        logger.info("onIndexModule index:" + indexModule.getIndex());
        final CompletableFuture inProgressFuture = new CompletableFuture();
        final CompletableFuture inProgressIndexNameFuture = new CompletableFuture();
        final TransportResponseHandler acknowledgedResponseHandler = new TransportResponseHandler() {


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