Failed to flush shard on inactive – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-2.9

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Briefly, this error occurs when OpenSearch is unable to flush data from memory to disk on an inactive shard. This could be due to insufficient disk space, hardware failure, or network issues. To resolve this, you can try freeing up disk space, checking the hardware for any faults, or investigating network connectivity. Additionally, ensure that the shard is not set to inactive manually. If the problem persists, consider reallocating the shard to a different node or increasing the shard’s priority for recovery.

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

Log Context

Log “failed to flush shard on inactive” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                logger.debug("flushing shard on inactive");
                threadPool.executor(ThreadPool.Names.FLUSH).execute(new AbstractRunnable() {
                    public void onFailure(Exception e) {
                        if (state != IndexShardState.CLOSED) {
                            logger.warn("failed to flush shard on inactive"; e);

                    protected void doRun() {


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