I want to write some custom schedulers for apache heron, and i'm diving a little deep into the source code. I noticed that in the heron source code there are couple of packages with similar classes. For example most of classes in backtype.storm & org.apache.storm are similar(exactly similar such that inside codes are identical). There are also some similar classes between these two packages and com.twitter.heron(for example com.twitter.heron.api.tuple.Fields) but some of them have different code inside(such as the Fields class). I know that when writing topologies we can import each package that we want and we can choose between either one of these but i'm curious about the differences between them and why they put all of these packages together. and didn't merge them? And if storm classes are the only choice for writing topologies, what are classes in com.twitter.heron package good for?
I know that heron is designed to be fully backward compatible with storm and this might be because of the backward compatibility issue, but i have to admit that this has confused me a lot, because i need to write my own code inside these classes and i don't know how to choose which one, which one is constantly developing and maintaining by developers and i should choose them as candidates to modify.
Thanks in advance.
Based on the Descriptions of the developer team in here:
Use of heron api classes is not recommended - since we might change them frequently. They are meant for internal usage only.
backtype.storm is if your application wants to use pre-storm 1.0.0. For post 1.0.0 applications, you should use org.apache.storm