Add ProcessGroupGloo::createDefaultDevice (#26166)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26166
There were 2 variants to create a new device. One to do so based the
name of a network interface, and one to do so based on a hostname or
address. In the latter, if the address was not specified, it would
lookup the local hostname and try to resolve that. If that failed, the
process would crash.
In this default path, we now try to lookup and use the local hostname,
and if that fails we fallback to using the loopback address.
If the local hostname doesn't resolve to an address that we can bind
to, it is very likely that this process won't join other processes
over the network, and that the user is trying to run a local test.
If this assumption is wrong, the user can override the default
interface selection by setting the environment variable
`GLOO_SOCKET_IFNAME` to the name of the external network interface.
I tested this by changing the local hostname to a bogus name and
confirmed that default initialization works as expected.
Closes #26049.
Test Plan: Imported from OSS
Differential Revision: D17397898
Pulled By: pietern
fbshipit-source-id: 95a2467761d89df87b520d6e5837b92184b0dc12
