recovery_engine_exception: recovery_engine_exception

What does it mean?

An engine-level error occurred during a shard's recovery, and the shard could not be opened successfully. Recovery is the step performed during a node restart, replica allocation or snapshot restore.

Why does it happen?

An underlying problem during recovery: corrupted Lucene segments or translog, insufficient disk space, file permissions, a network interruption between source and target nodes, or version/compatibility problems. It usually wraps a more specific sub-error (corruption, I/O).

How to fix it

Inspect the underlying (caused_by) error to identify the real problem (corruption, disk, network, etc.). Verify disk space and file permissions. If replica allocation fails, see why with _cluster/allocation/explain and trigger reallocation if needed. If there is corruption, recover from a healthy replica/snapshot. If it is network-related, check inter-node connectivity and recovery settings.