Diagram of the whole process of Kafka's Consumer obtaining consumption data

This article is used as a supplement to: [Follow me with Consumer Analysis of Kafka Source Code](http://flychao88.iteye.com/blog/2268481), students who have seen our previous source code analysis may know.

This article will sort out the whole process of how the client program calls the Consumer to get the final Kafka message in a diagrammatic way at the source level.