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
+ indexSettings.getIndex()
                + " does not have soft deletes enabled";
            assert false : message;
            throw new IllegalStateException(message);
        }
    }
    /**
     * Get all retention leases tracked on this shard.
     *
     * @return the retention leases
     */
    public RetentionLeases getRetentionLeases() {
        return getRetentionLeases(false);
    }
    /**
     * If the expire leases parameter is false, gets all retention leases tracked on this shard and otherwise first calculates
     * expiration of existing retention leases, and then gets all non-expired retention leases tracked on this shard. Note that only the
     * primary shard calculates which leases are expired, and if any have expired, syncs the retention leases to any replicas. If the
     * expire leases parameter is true, this replication tracker must be in primary mode.
     *
     * @return the non-expired retention leases
     */
    public RetentionLeases getRetentionLeases(final boolean expireLeases) {
        assert expireLeases == false || assertPrimaryMode();
        verifyNotClosed();
        return replicationTracker.getRetentionLeases(expireLeases);
    }
    public RetentionLeaseStats getRetentionLeaseStats() {
        verifyNotClosed();
        return new RetentionLeaseStats(getRetentionLeases());