Class: ServiceSkeleton::SignalManager

Inherits:
Object
  • Object
show all
Includes:
LoggingHelpers
Defined in:
lib/service_skeleton/signal_manager.rb

Overview

Manage signals in a sane and safe manner.

Signal handling is a shit of a thing. The code that runs when a signal is triggered can't use mutexes (which are used in all sorts of places you might not expect, like Logger!) or anything else that might block. This greatly constrains what you can do inside a signal handler, so the standard approach is to stuff a character down a pipe, and then have the real signal handling run later.

Also, there's always the (slim) possibility that something else might have hooked into a signal we want to receive. Because only a single signal handler can be active for a given signal at a time, we need to "chain" the existing handler, by calling the previous signal handler from our signal handler after we've done what we need to do. This class takes care of that, too, because it's a legend.

So that's what this class does: it allows you to specify signals and associated blocks of code to run, it sets up signal handlers which send notifications to a background thread and chain correctly, and it manages the background thread to receive the notifications and execute the associated blocks of code outside of the context of the signal handler.

Instance Method Summary collapse

Constructor Details

#initialize(logger:, counter:, signals:) ⇒ SignalManager

Setup a signal handler instance.

Parameters:

  • logger (Logger) —

    the logger to use for all the interesting information about what we're up to.



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# File 'lib/service_skeleton/signal_manager.rb', line 36

def initialize(logger:, counter:, signals:)
  @logger, @signal_counter, @signal_list = logger, counter, signals

  @registry = Hash.new { |h, k| h[k] = SignalHandler.new(k) }

  @signal_list.each do |sig, proc|
    @registry[signum(sig)] << proc
  end
end

Instance Method Details

#run ⇒ Object 



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# File 'lib/service_skeleton/signal_manager.rb', line 46

def run
  logger.info(logloc) { "Starting signal manager for #{@signal_list.length} signals" }

  @r, @w = IO.pipe

  install_signal_handlers

  signals_loop
ensure
  remove_signal_handlers
end

#shutdown ⇒ Object 



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# File 'lib/service_skeleton/signal_manager.rb', line 58

def shutdown
  @r.close
end