Add support for worker pre_shutdown_timeout

[amenon]

Resque has had support for a pre_shutdown_timeout for a worker since v1.27.3 (resque/resque#1514).

The time between the parent receiving a shutdown signal (TERM by default) and it sending that signal on to the child process. Designed to give the child process time to complete before being forced to die.

This PR adds support for this attribute in the forked workers.

[nevans]

I wonder if this is needed, and if so, why? Doesn't Resque::Worker#initialize already set it for itself:

    def initialize(*queues)
      @shutdown = nil
      @paused = nil
      @before_first_fork_hook_ran = false

      @heartbeat_thread = nil
      @heartbeat_thread_signal = nil

      @last_state = :idle

      verbose_value = ENV['LOGGING'] || ENV['VERBOSE']
      self.verbose = verbose_value if verbose_value
      self.very_verbose = ENV['VVERBOSE'] if ENV['VVERBOSE']
      self.pre_shutdown_timeout = (ENV['RESQUE_PRE_SHUTDOWN_TIMEOUT'] || 0.0).to_f
      self.term_timeout = (ENV['RESQUE_TERM_TIMEOUT'] || 4.0).to_f
      self.term_child = ENV['TERM_CHILD']
      self.graceful_term = ENV['GRACEFUL_TERM']
      self.run_at_exit_hooks = ENV['RUN_AT_EXIT_HOOKS']

      self.queues = queues
    end

Of course, the same question could be asked of the other config attributes set from environment variables in that method! So, I just looked at some versions of that method from earlier git tags, and it looks like it was updated to initialize itself from environment variables with version 1.26.0 (see also: version 1.25.2).

So, if this config setting was added by v1.27.3, I'm thinking that maybe we don't need to add it here? If the environment variable isn't updating the configuration (or achieving the desired results) maybe something else is wrong?

For what it's worth, the next time we make significant changes to this gem, its dependencies will probably be updated to require either resque >= 1.27. or 2.0.

[nevans]

If you can show that this is needed, I'll merge it... I don't think it is though. The version of resque that has that config attribute will also set the config from the environment variable itself.

[amenon]

Thank you for the quick review @nevans. You are right that resque will load that config from the system environment variable. My initial test was this was flawed, but I have now verified that this works correctly. Sorry for wasting your time.

[nevans]

@amenon no prob. I'm glad it worked out for you.