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
}
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            out.writeCollection(values());
            if (out.getVersion().onOrAfter(StoreStats.RESERVED_BYTES_VERSION)) {
                out.writeBoolean(complete);
            }
        }
        @Override
        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
            if (params.paramAsBoolean("detailed", false)) {
                builder.xContentList(Fields.DETAILS, values(), params);
            }
            return builder;
        }
        public void addFileDetails(String name, long length, boolean reused) {
            assert complete == false : "addFileDetail for [" + name + "] when file details are already complete";
            FileDetail existing = fileDetails.put(name, new FileDetail(name, length, reused));
            assert existing == null : "file [" + name + "] is already reported";
        }
        public void addRecoveredBytesToFile(String name, long bytes) {
            FileDetail file = fileDetails.get(name);
            assert file != null : "file [" + name + "] hasn't been reported";
            file.addRecoveredBytes(bytes);
        }
        public void resetRecoveredBytesOfFile(String name) {
            FileDetail file = fileDetails.get(name);
            assert file != null : "file [" + name + "] hasn't been reported";
            file.resetRecoveredBytes();