Module: Async::Background::Scheduler

Defined in:
lib/async/background/scheduler.rb

Defined Under Namespace

Classes: Unavailable, UnknownScheduler

Constant Summary collapse

ENV_KEY = 
'ASYNC_BACKGROUND_SCHEDULER'
THREAD_ENV_KEY = 
'ASYNC_BACKGROUND_SCHEDULER_THREAD'
KNOWN = 
%i[async itsi].freeze

Class Method Summary collapse

Class Method Details

.available?(feature) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/async/background/scheduler.rb', line 61

def available?(feature)
  !Gem.find_files(feature).empty? || !Gem.find_files("#{feature}.rb").empty?
rescue StandardError
  try_require(feature)
end

.current ⇒ Object 



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# File 'lib/async/background/scheduler.rb', line 19

def current
  return nil unless installed?

  Fiber.scheduler.class.name
end

.detect ⇒ Object

Raises:



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# File 'lib/async/background/scheduler.rb', line 51

def detect
  return :async if defined?(::Async::Scheduler)
  return :itsi if defined?(::Itsi::Scheduler)

  return :async if available?('async')
  return :itsi if available?('itsi/scheduler')

  raise Unavailable, 'no fiber scheduler available: add `async` or `itsi-scheduler` to your bundle'
end

.installed? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/async/background/scheduler.rb', line 17

def installed? = !Fiber.scheduler.nil?

.preload!(kind = nil) ⇒ Object 



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# File 'lib/async/background/scheduler.rb', line 25

def preload!(kind = nil)
  case resolve(kind)
  when :async then require 'async'
  when :itsi then require 'itsi/scheduler'
  end
  true
end

.resolve(kind = nil) ⇒ Object

Raises:



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# File 'lib/async/background/scheduler.rb', line 43

def resolve(kind = nil)
  name = (kind || ENV.fetch(ENV_KEY, 'auto')).to_s.downcase
  return name.to_sym if KNOWN.include?(name.to_sym)
  return detect if name == 'auto'

  raise UnknownScheduler, "unknown scheduler #{name.inspect}, expected one of: #{KNOWN.join(', ')}, auto"
end

.run(kind = nil, &block) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/async/background/scheduler.rb', line 33

def run(kind = nil, &block)
  raise ArgumentError, 'block required' unless block
  return block.call if installed?

  case resolve(kind)
  when :async then run_async(&block)
  when :itsi then run_itsi(&block)
  end
end

.run_async(&block) ⇒ Object 



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# File 'lib/async/background/scheduler.rb', line 74

def run_async(&block)
  require 'async'

  result = nil
  send(:Async) { result = block.call }
  result
end

.run_itsi(&block) ⇒ Object 



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# File 'lib/async/background/scheduler.rb', line 82

def run_itsi(&block)
  require 'itsi/scheduler'

  return run_on_thread(::Itsi::Scheduler, &block) if threaded?

  run_on_current_thread(::Itsi::Scheduler.new, &block)
end

.run_on_current_thread(scheduler, &block) ⇒ Object 



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# File 'lib/async/background/scheduler.rb', line 94

def run_on_current_thread(scheduler, &block)
  result = nil
  failure = nil
  finished = false

  previous = Fiber.scheduler
  Fiber.set_scheduler(scheduler)

  begin
    Fiber.schedule do
      result = block.call
    rescue Exception => e # rubocop:disable Lint/RescueException
      failure = e
    ensure
      finished = true
    end

    scheduler.run if scheduler.respond_to?(:run)
  ensure
    Fiber.set_scheduler(previous)
  end

  raise failure if failure
  unless finished
    raise Unavailable,
          "#{scheduler.class} did not run the scheduled fiber to completion on close; " \
          "set #{THREAD_ENV_KEY}=1 to fall back to a dedicated scheduler thread"
  end

  result
end

.run_on_thread(scheduler_class, &block) ⇒ Object 



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# File 'lib/async/background/scheduler.rb', line 126

def run_on_thread(scheduler_class, &block)
  result = nil
  failure = nil

  thread = Thread.new do
    Fiber.set_scheduler(scheduler_class.new)
    Fiber.schedule do
      result = block.call
    rescue Exception => e # rubocop:disable Lint/RescueException
      failure = e
    end
  end
  thread.join
  raise failure if failure

  result
end

.threaded? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/async/background/scheduler.rb', line 90

def threaded?
  %w[1 true yes].include?(ENV.fetch(THREAD_ENV_KEY, '').to_s.downcase)
end

.try_require(feature) ⇒ Object 



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# File 'lib/async/background/scheduler.rb', line 67

def try_require(feature)
  require feature
  true
rescue LoadError
  false
end