Is there any material introducing how to program Endpoint with protobuf tech?

[donhoff_h]

Hi, experts.

I am studying how to program an Endpoint. 
The material I have is a book "HBase The Definitive Guide(3rd)". I also read 
the blog "https://blogs.apache.org/hbase/entry/coprocessor_introduction‍";. But 
it seems that the Endpoint has been changed to use ProtoBuf tecknique. So I 
feel the above two materials can not guide me step by step to write an Endpoint 
program. Is there any material which teaches us systematically how to write an 
Endpoint program with ProtoBuf tech? 

Many Thanks!