How to set the thread number of callback_server

[张帅]

When Server In callback mode, it has only four thread can accept the request from  Clients in the same time.So, i want to know how to  change the  thread number of callback_server.

Sorry for my poor english, have a good day!

[Oleg Linkin]

Hi.

> Currently, the thread count is automatically selected by the library with no user input and is set to half the system's core count, but no less than 2 and no more than 16.

https://github.com/grpc/proposal/blob/master/L67-cpp-callback-api.md

[Oleg Linkin]

Also: https://github.com/grpc/grpc/blob/master/src/cpp/common/completion_queue_cc.cc#L56