Hi, guys I’m working together with Doc. Huang to refactor cluster module. Right now, I’m working on the client pool refactor. At first I want to extract some interfaces like `ClientPool`, `ClientFactory`, etc.
But as the work going, I found my design is very similar to what apache commons pool does. I decide to import the external library `apache commons pool` to help refine the current client pool implements. Any concern please let me know. Thanks! Jianyun Cheng
