[Reland] TCPStore add watchKey method and new listener thread (#56217)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56217
Reland of https://github.com/pytorch/pytorch/pull/54264
Changes:
- Update socket send() to use flag MSG_NOSIGNAL to prevent SIGPIPE because error in return is already capturad
- Update watchKey to block until callback has been registered on master.
- Fix race condition in testWatchKeyCallback which caused flaky test failures.
Test:
Ran TCPStoreTest 100 times locally with no errors, running [ci-all tests](https://github.com/pytorch/pytorch/pull/56219)
Test Plan: Imported from OSS
Reviewed By: mrshenli
Differential Revision: D27824802
Pulled By: H-Huang
fbshipit-source-id: c32230ce726d7d848b9896a63aa52b8eb04a0a2d
