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/index/shard/IndexShard.java
getEngine().failEngine(reason, e);
    }
    /**
     * Acquires a point-in-time reader that can be used to create {@link Engine.Searcher}s on demand.
     */
    public Engine.SearcherSupplier acquireSearcherSupplier() {
        return acquireSearcherSupplier(Engine.SearcherScope.EXTERNAL);
    }
    /**
     * Acquires a point-in-time reader that can be used to create {@link Engine.Searcher}s on demand.
     */
    public Engine.SearcherSupplier acquireSearcherSupplier(Engine.SearcherScope scope) {
        readAllowed();
        markSearcherAccessed();
        final Engine engine = getEngine();
        return engine.acquireSearcherSupplier(this::wrapSearcher, scope);
    }
    public Engine.Searcher acquireSearcher(String source) {
        readAllowed();
        markSearcherAccessed();
        final Engine engine = getEngine();
        return engine.acquireSearcher(source, Engine.SearcherScope.EXTERNAL, this::wrapSearcher);
    }
    private void markSearcherAccessed() {
        lastSearcherAccess.lazySet(threadPool.relativeTimeInMillis());
    }
    private Engine.Searcher wrapSearcher(Engine.Searcher searcher) {
        assert ElasticsearchDirectoryReader.unwrap(searcher.getDirectoryReader()) != null
            : "DirectoryReader must be an instance or ElasticsearchDirectoryReader";