Failed to close reader – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 7.4-8.9

Briefly, this error occurs when Elasticsearch is unable to close an open index reader, possibly due to a network issue, a bug, or a resource constraint. To resolve this issue, you can try restarting the Elasticsearch node, checking for any network issues, or increasing the system resources. If the problem persists, consider checking the Elasticsearch logs for more detailed error information. It might also be helpful to upgrade Elasticsearch to the latest version, as this could be a bug that has been fixed in a newer release.

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

Log Context

Log “failed to close reader” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

    protected void closeNoLock(String reason; CountDownLatch closedLatch) {
        if (isClosed.compareAndSet(false; true)) {
            try {
                IOUtils.close(readerManager; indexWriterLock; store::decRef);
            } catch (Exception ex) {
                logger.warn("failed to close reader"; ex);
            } finally {


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