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
}
        public void addRecoveredFromSnapshotBytesToFile(String name, long bytes) {
            FileDetail file = fileDetails.get(name);
            assert file != null : "file [" + name + "] hasn't been reported";
            file.addRecoveredFromSnapshotBytes(bytes);
        }
        public FileDetail get(String name) {
            return fileDetails.get(name);
        }
        public void setComplete() {
            complete = true;
        }
        public int size() {
            return fileDetails.size();
        }
        public boolean isEmpty() {
            return fileDetails.isEmpty();
        }
        public void clear() {
            fileDetails.clear();
            complete = false;
        }
        public Collection<FileDetail> values() {
            return fileDetails.values();
        }
        public boolean isComplete() {
            return complete;
        }
    }
    public static class Index extends Timer implements ToXContentFragment, Writeable {