This is somehow related with our team's work(https://fate.suse.com/323437), We want to write a set of restful API for any components in HA product stack use to control the cluster.
This work/fate is in early stage so that the implementation about using what framework/language is still on evaluating.
I personally prefer to use Flask, cause Flask is a quick-development framework and can easily integrated with any python-implemented components like crmsh, SUMA and saltstack.
I have already created a repo in github as starting porint: https://github.com/liangxin1300/ClusterAPI
This project is one of its kind!