Include rank of default PG in C++ log messages (#110623)
I tested by adding some warning logs in C++, run a distributed program and show that they now had `[rank0]:` in the messages. There is no existing test infra for C++ logging so I couldn't easily add a unit test.
The implementation strategy is to setup a global variable in C++, and then poke it when we initialize a process group. This was the simplest thing I could think of that would work.
This PR only works for non-glog logging. Probably need to come up with some other strategy for glog, e.g., a custom prefix, but need to make sure this doesn't conflict with fbcode. I can't easily test this from OSS, will leave as follow up work.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/110623
Approved by: https://github.com/voznesenskym, https://github.com/wanchaol, https://github.com/fduwjj
