Add custom pause, resume and alive? Process methods

[djberg96]

This PR extends the Process module to include pause, resume and alive? methods.

The Unix implementation is fairly straightforward, simply using SIGSTOP and SIGCONT. The Windows implementation was trickier, and required the use of an ffi wrapper (here I used fiddle from the standard library).

WIP for now until I add some specs. But, I can tell you that in local examples it worked as expected.

The only quirk I noticed was on Windows it would not immediately respond to an event, e.g. SIGINT, but would instead defer until the process was resumed, whereas on unixy systems it appeared to react immediately, e.g. you could ctrl-c out of a paused process. But, I couldn't tell you if one of these is more "correct" than the other.

The ultimate goal is to remove the custom MiqProcess module from gems-pending.

[Fryguy]

@bdunne Thoughts?

[djberg96]

@Fryguy ok, updated readme.

[Fryguy]

Looks good @djberg96 ... I think we are just waiting on specs.

[djberg96]

@Fryguy, @NickLaMuro suggestions for testing an external process?

[NickLaMuro]

suggestions for testing an external process?

🤔

This is the best I can come up with at the moment...

• Spawn a process that is basically a loop that writes to a log every few ticks
  • probably can just be another ruby process with %x[#{Gem.ruby} -e "loop; ...; end"]
• wait a bit (sleep)
• Check the process is .alive?
• .pause the process and check how many lines were written
• wait a bit
• read the log file again and check again that the lines still match
• .resume the process
• wait a bit
• confirm new lines have been written
• kill the process

[djberg96]

@NickLaMuro I don't know if it's an option, but I did see this: https://github.com/jpastuszek/rspec-background-process

[djberg96]

@NickLaMuro Ok, I've add some specs, please let me know what you think.

Note that while I did insert some code to make the Windows version cross-platform, the current specs do not currently pass on Windows. This is because getting process status information on Windows is more difficult.

There is a status field in the Win32_Process object, but unfortunately it's always null (as per the documentation). On Windows you can't get process status, you can only get thread status. While it's possible to get this information, it would require adding more code to sys-proctable, which I don't want to worry about right now, especially since Windows doesn't matter to us atm.

[djberg96]

@miq-bot remove_label wip

[djberg96]

@NickLaMuro, @Fryguy, @jrafanie I think it's ready to go. :)

[miq-bot]

Checked commits https://github.com/djberg96/more_core_extensions/compare/e8f0676bf9e36b3955f03286bd94ed403f5d5217~...7cad6e57c775867349da5cee1bda8b7df7388f00 with ruby 2.5.7, rubocop 0.69.0, haml-lint 0.20.0, and yamllint 4 files checked, 3 offenses detected

spec/core_ext/process/pause_resume_spec.rb

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