1. closure should be managed by a unique ptr and released by brpc , should not hold by our code. If hold by our code, we need to wait brpc finished during cancel or close.
2. closure should be exception safe, if any exception happens, should not memory leak.
3. using a specific callback interface to be implemented by Doris's code, we could write any code and doris should manage callback's lifecycle.
4. using a weak ptr between callback and closure. If callback is deconstruted before closure'Run, should not core.
8cf360fff7