@Override
    public int appendFrom(ByteBuffer buffer) {
      ByteBuffer buf = ByteBuffer.allocate(buffer.remaining());
      buf.put(buffer);
      buf.flip();
      storeBuf(buf);
      return buf.capacity();
    }
Log that stores all data in memory.
ambry-replication/src/test/java/com/github/ambry/replication/InMemoryStore.java