@Override
  public boolean isOpen() {
    return channelOpen.get();
  }
Constructs a {@link ReadableStreamChannel} whose read operations return data from the provided {@code buf}.
@param buf the {@link ByteBuf} that is used to retrieve data from on invocation of read operations.
ambry-test-utils/src/main/java/com/github/ambry/commons/ByteBufReadableStreamChannel.java