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
refreshListeners.setMaxIssuedSeqNoSupplier(newEngine::getMaxSeqNo);
    }
    /**
     * called if recovery has to be restarted after network error / delay **
     */
    public void performRecoveryRestart() throws IOException {
        assert Thread.holdsLock(mutex) == false : "restart recovery under mutex";
        synchronized (engineMutex) {
            assert refreshListeners.pendingCount() == 0 : "we can't restart with pending listeners";
            IOUtils.close(currentEngineReference.getAndSet(null));
            resetRecoveryStage();
        }
    }
    /**
     * If a file-based recovery occurs, a recovery target calls this method to reset the recovery stage.
     */
    public void resetRecoveryStage() {
        assert routingEntry().recoverySource().getType() == RecoverySource.Type.PEER : "not a peer recovery [" + routingEntry() + "]";
        assert currentEngineReference.get() == null;
        if (state != IndexShardState.RECOVERING) {
            throw new IndexShardNotRecoveringException(shardId, state);
        }
        recoveryState().setStage(RecoveryState.Stage.INIT);
    }
    /**
     * returns stats about ongoing recoveries, both source and target
     */
    public RecoveryStats recoveryStats() {
        return recoveryStats;
    }