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 DocsStats docStats() {
        readAllowed();
        return getEngine().docStats();
    }
    /**
     * @return {@link CommitStats}
     * @throws AlreadyClosedException if shard is closed
     */
    public CommitStats commitStats() {
        return getEngine().commitStats();
    }
    /**
     * @return {@link SeqNoStats}
     * @throws AlreadyClosedException if shard is closed
     */
    public SeqNoStats seqNoStats() {
        return getEngine().getSeqNoStats(replicationTracker.getGlobalCheckpoint());
    }
    public IndexingStats indexingStats() {
        Engine engine = getEngineOrNull();
        final boolean throttled;
        final long throttleTimeInMillis;
        if (engine == null) {
            throttled = false;
            throttleTimeInMillis = 0;
        } else {
            throttled = engine.isThrottled();
            throttleTimeInMillis = engine.getIndexThrottleTimeInMillis();
        }
        return internalIndexingStats.stats(throttled, throttleTimeInMillis);