pytorch

59cd0fae - Defer pg agent listener thread until contexts are initialized (#28013)

Defer pg agent listener thread until contexts are initialized (#28013) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/28013 ProcessGroupAgent currently kicks off the listener thread in its constructor. However, serving requests requires contexts to be initialized, e.g., RRefContext and agent_ global var in api.py, which might not be done yet when the first request arrives. ProcessGroupAgent does not know what would be the appropriate time to start the listener thread, hence exposing an API for higher layer code to explicitly start listeners. Test Plan: Imported from OSS Differential Revision: D17932271 Pulled By: mrshenli fbshipit-source-id: 3b408477594d4d19319e7cd08dd6f383a7ed7670