Pluggable metadata storage for Helix - MetaClient library #2237
Description
Is your feature request related to a problem? Please describe.
Helix is a large and powerful complex system containing many sub-modules. Currently, Helix logic in all these submodules is heavily dependent on Zookeeper.
With the growth of number of user data, existing ZooKeeper cluster may facing scalability issue. It is hard to migrate any Helix service to another metadata service with the current convoluted ZkClient structure.
Describe the solution you'd like
We will provide a MetaClient library. It contains a generic metadata access interfaces as well as widely used functionality oriented classes build on top of the it. The generic metadata access client interfaces can be implemented into multiple flavors that take advantage of different underlying metadata stores.