[DISCUSS] default ports in cluster module

[Xiangdong Huang <sa...@gmail.com>]

Hi,

Currently, the cluster module uses 4 ports:
- rpc port: 55560
- internal meta port: 9003 by default
- heartbeat port: 9004 by default
- internal data port: 40010 by default

1. I'd like to migrate the rpc port to 6667 to keep consistent with the
single node version;
To help debugging, we can add a parameter `debug_rpc_port` to active the
rpc service in the server module in the cluster version.

2. 9003 port is... quite... different with other ports... (As others are >=
40K and 50K).
I think either enlarge the meta port or reduce the data port.

Best,
-----------------------------------
Xiangdong Huang
School of Software, Tsinghua University

 黄向东
清华大学 软件学院