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
public void persistRetentionLeases() throws WriteStateException {
        verifyNotClosed();
        replicationTracker.persistRetentionLeases(path.getShardStatePath());
    }
    public boolean assertRetentionLeasesPersisted() throws IOException {
        return replicationTracker.assertRetentionLeasesPersisted(path.getShardStatePath());
    }
    /**
     * Syncs the current retention leases to all replicas.
     */
    public void syncRetentionLeases() {
        assert assertPrimaryMode();
        verifyNotClosed();
        replicationTracker.renewPeerRecoveryRetentionLeases();
        final RetentionLeases retentionLeases = getRetentionLeases(true);
        logger.trace("background syncing retention leases [{}] after expiration check", retentionLeases);
        retentionLeaseSyncer.backgroundSync(shardId, shardRouting.allocationId().getId(), getPendingPrimaryTerm(), retentionLeases);
    }
    /**
     * Called when the recovery process for a shard has opened the engine on the target shard. Ensures that the right data structures
     * have been set up locally to track local checkpoint information for the shard and that the shard is added to the replication group.
     *
     * @param allocationId  the allocation ID of the shard for which recovery was initiated
     */
    public void initiateTracking(final String allocationId) {
        assert assertPrimaryMode();
        replicationTracker.initiateTracking(allocationId);
    }
    /**
     * Marks the shard with the provided allocation ID as in-sync with the primary shard. See