@Override
  public KeyValueIterator<byte[], byte[]> all() {
    this.metrics.alls().inc();
    return new InMemoryIterator(this.underlying.entrySet().iterator(), this.metrics);
  }
@param metrics A metrics instance to publish key-value store related statistics
samza-kv-inmemory/src/main/java/org/apache/samza/storage/kv/inmemory/InMemoryKeyValueStore.java