Support thread group about fail-rs

[BusyJay]

/cc @brson @Little-Wallace @lucab

[lucab]

@BusyJay nice! A bunch of high-level questions:

• can the thread-group logic be folded into FailScenario? register_current doesn't seem to be very different from threadgroup-bound setup.
• would it be better for the API to take a ThreadId argument instead?
• I have no idea how this would actually work at the low level; how do you intend to plug this into the eval logic?

[BusyJay]

can the thread-group logic be folded into FailScenario?

FailGroup can be accessed via a global fuction, so it may not be appropriate to use FailScenario directly. But I think it can be defined as a field of FailScenario if necessary.

would it be better for the API to take a ThreadId argument instead?

I'm not sure. I find it more convenient to just register current thread instead of others. For example, thread pool generally provides after_start, before_stop hooks to allow do work in a thread, but generally won't provide thread ID directly.

plug this into the eval logic?

When evaluating, it uses current thread ID to find out which thread group it belongs to, and then check the rules of the group.

[Little-Wallace]

It seems complex. Why can not we launch multiple process and each process runs some test with a single thread?

[BusyJay]

Process isn't compatible with the default test runner.