I have posted this question in StackOverflow: https://stackoverflow.com/questions/61334549/flink-richsinkfunction-constructor-vs-open
The question is: > Let's say I need to implemnt a custom sink using RichSinkFunction, and I need some variables like DBConnection in the sink. Where should I initialize the DBConnection？ I see most of the articles init the DBConnection in the open() method, why not in the constructor? A folow up questions is what kind of variables should be inited in constructor and what should be init in open()?
