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
return length;
        }
        /**
         * number of bytes recovered for this file (so far). 0 if the file is reused *
         */
        public long recovered() {
            return recovered;
        }
        /**
         * number of bytes recovered from this file (so far) from a snapshot.
         */
        public long recoveredFromSnapshot() {
            return recoveredFromSnapshot;
        }
        /**
         * returns true if the file is reused from a local copy
         */
        public boolean reused() {
            return reused;
        }
        boolean fullyRecovered() {
            return reused == false && length == recovered;
        }
        @Override
        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
            builder.startObject();
            builder.field(Fields.NAME, name);
            builder.humanReadableField(Fields.LENGTH_IN_BYTES, Fields.LENGTH, new ByteSizeValue(length));
            builder.field(Fields.REUSED, reused);
            builder.humanReadableField(Fields.RECOVERED_IN_BYTES, Fields.RECOVERED, new ByteSizeValue(recovered));