@Override
    public void close() {
        Utils.closeQuietly(backingStore != null ? backingStore::stop : null, "backing store for offset syncs");
        Utils.closeQuietly(admin, "admin client for offset syncs");
    }
Start the OffsetSyncStore, blocking until all previous Offset Syncs have been read from backing storage.
connect/mirror/src/main/java/org/apache/kafka/connect/mirror/OffsetSyncStore.java