Unexpected error during recovery recoveryId failing shard – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.3-8.9

Briefly, this error occurs when Elasticsearch encounters an unexpected issue during the recovery process of a shard. This could be due to hardware failure, network issues, or data corruption. To resolve this, you can try the following: 1) Check the hardware and network status to ensure they are functioning properly. 2) Look at the Elasticsearch logs for more detailed error messages. 3) If data corruption is suspected, consider restoring the shard from a backup. 4) If the issue persists, you may need to delete and recreate the index.

This guide will help you check for common problems that cause the log ” unexpected error during recovery [” + recoveryId + “]; failing shard ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: indices, recovery, shard.

Log Context

Log “unexpected error during recovery [” + recoveryId + “]; failing shard” classname is PeerRecoveryTargetService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

        public void onFailure(Exception e) {
            try (RecoveryRef recoveryRef = onGoingRecoveries.getRecovery(recoveryId)) {
                if (recoveryRef != null) {
                    logger.error(() -> "unexpected error during recovery [" + recoveryId + "]; failing shard"; e);
                        new RecoveryFailedException(recoveryRef.target().state(); "unexpected error"; e);
                        true // be safe


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