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/indices/recovery/RecoveryState.java
primary = in.readBoolean();
    }
    @Override
    public void writeTo(StreamOutput out) throws IOException {
        timer.writeTo(out);
        out.writeByte(stage.id());
        shardId.writeTo(out);
        recoverySource.writeTo(out);
        targetNode.writeTo(out);
        out.writeOptionalWriteable(sourceNode);
        index.writeTo(out);
        translog.writeTo(out);
        verifyIndex.writeTo(out);
        out.writeBoolean(primary);
    }
    public ShardId getShardId() {
        return shardId;
    }
    public synchronized Stage getStage() {
        return this.stage;
    }
    protected void validateAndSetStage(Stage expected, Stage next) {
        if (stage != expected) {
            assert false : "can't move recovery to stage [" + next + "]. current stage: [" + stage + "] (expected [" + expected + "])";
            throw new IllegalStateException(
                "can't move recovery to stage [" + next + "]. current stage: [" + stage + "] (expected [" + expected + "])"
            );
        }
        stage = next;
    }