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

Opster Team

Aug-23, Version: 7.7-8.9

Briefly, this error occurs when Elasticsearch is unable to flush data from memory to disk on an inactive shard. This could be due to insufficient disk space, a faulty disk, or a network issue. To resolve this, you can try freeing up disk space, checking the health of your disk, or investigating network connectivity. Additionally, ensure that your Elasticsearch cluster is properly configured and that the shard is not being accessed by another process during the flush operation.

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 Elasticsearch concepts: index, flush, shard.

Log Context

Log “failed to flush shard on inactive” classname is
We extracted the following from Elasticsearch 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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