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
private volatile long checkIndexTime;
        public VerifyIndex() {}
        public VerifyIndex(StreamInput in) throws IOException {
            super(in);
            checkIndexTime = in.readVLong();
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            super.writeTo(out);
            out.writeVLong(checkIndexTime);
        }
        public void reset() {
            super.reset();
            checkIndexTime = 0;
        }
        public long checkIndexTime() {
            return checkIndexTime;
        }
        public void checkIndexTime(long checkIndexTime) {
            this.checkIndexTime = checkIndexTime;
        }
        @Override
        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
            builder.humanReadableField(Fields.CHECK_INDEX_TIME_IN_MILLIS, Fields.CHECK_INDEX_TIME, new TimeValue(checkIndexTime));
            builder.humanReadableField(Fields.TOTAL_TIME_IN_MILLIS, Fields.TOTAL_TIME, new TimeValue(time()));
            return builder;
        }
    }
    public static class Translog extends Timer implements ToXContentFragment, Writeable {