Hi @mathieu-wang, thanks for your comment!

Oh, I missed it. But, ummm...I think GerritServer should have it. Because:
* GerritSendCommandQueue has work queue and thread.
* All subsequent commands to send for each servers would be stacked if one of server has any connection issue.

So...I decided to back numberOfSendingWorkerThreads into Config at first. Then new pull request to change GerritSendCommandQueue to non-singleton class would be needed.