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
builder.startObject(Fields.FILES);
            builder.field(Fields.TOTAL, totalFileCount());
            builder.field(Fields.REUSED, reusedFileCount());
            builder.field(Fields.RECOVERED, recoveredFileCount());
            builder.field(Fields.PERCENT, String.format(Locale.ROOT, "%1.1f%%", recoveredFilesPercent()));
            fileDetails.toXContent(builder, params);
            builder.endObject();
            builder.humanReadableField(Fields.TOTAL_TIME_IN_MILLIS, Fields.TOTAL_TIME, new TimeValue(time()));
            builder.humanReadableField(Fields.SOURCE_THROTTLE_TIME_IN_MILLIS, Fields.SOURCE_THROTTLE_TIME, sourceThrottling());
            builder.humanReadableField(Fields.TARGET_THROTTLE_TIME_IN_MILLIS, Fields.TARGET_THROTTLE_TIME, targetThrottling());
            return builder;
        }
        @Override
        public synchronized String toString() {
            try {
                XContentBuilder builder = XContentFactory.jsonBuilder().prettyPrint();
                builder.startObject();
                toXContent(builder, EMPTY_PARAMS);
                builder.endObject();
                return Strings.toString(builder);
            } catch (IOException e) {
                return "{ \"error\" : \"" + e.getMessage() + "\"}";
            }
        }
        public synchronized FileDetail getFileDetails(String dest) {
            return fileDetails.get(dest);
        }
    }
}