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
} else {
                sourceThrottlingInNanos += timeInNanos;
            }
        }
        public synchronized void addTargetThrottling(long timeInNanos) {
            if (targetThrottleTimeInNanos == UNKNOWN) {
                targetThrottleTimeInNanos = timeInNanos;
            } else {
                targetThrottleTimeInNanos += timeInNanos;
            }
        }
        public synchronized TimeValue sourceThrottling() {
            return TimeValue.timeValueNanos(sourceThrottlingInNanos);
        }
        public synchronized TimeValue targetThrottling() {
            return TimeValue.timeValueNanos(targetThrottleTimeInNanos);
        }
        /**
         * total number of files that are part of this recovery, both re-used and recovered
         */
        public synchronized int totalFileCount() {
            return fileDetails.size();
        }
        /**
         * total number of files to be recovered (potentially not yet done)
         */
        public synchronized int totalRecoverFiles() {
            int total = 0;
            for (FileDetail file : fileDetails.values()) {
                if (file.reused() == false) {