We saw a case where the recovery stats reported `recovered_bytes` greater than `length_in_bytes` for one file:

```
GET /_recovery?detailed

200 OK
...
{
  "name": "_buk.fdt",
  "length_in_bytes": 26891307173,
  "reused": false,
  "recovered_in_bytes": 35324928266,
  "recovered_from_snapshot_in_bytes": 8433621093
}
...
```

NB `35324928266 == 26891307173 + 8433621093`

This causes Elasticsearch to compute a negative value for the reserved space on the target node of this recovery, which prevents stats APIs from working. This appears to be caused by a network-level failure which triggers a retry without first cancelling an ongoing download of a different file with the same name from the snapshot repository.

---

### Workaround

Restart the target node to clear these stats.
server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
if (state != IndexShardState.CLOSED) {
                logger.warn("Failed to perform engine refresh", e);
            }
        }
    }
    /**
     * Called when our shard is using too much heap and should move buffered indexed/deleted documents to disk.
     */
    public void writeIndexingBuffer() {
        try {
            Engine engine = getEngine();
            engine.writeIndexingBuffer();
        } catch (Exception e) {
            handleRefreshException(e);
        }
    }
    /**
     * Notifies the service to update the local checkpoint for the shard with the provided allocation ID. See
     * {@link ReplicationTracker#updateLocalCheckpoint(String, long)} for
     * details.
     *
     * @param allocationId the allocation ID of the shard to update the local checkpoint for
     * @param checkpoint   the local checkpoint for the shard
     */
    public void updateLocalCheckpointForShard(final String allocationId, final long checkpoint) {
        assert assertPrimaryMode();
        verifyNotClosed();
        replicationTracker.updateLocalCheckpoint(allocationId, checkpoint);
    }
    /**