Class: Async::Task

Inherits:
Node
  • Object
show all
Extended by:
Forwardable
Defined in:
lib/async/task.rb

Overview

A task represents the state associated with the execution of an asynchronous block.

Instance Attribute Summary collapse

Attributes inherited from Node

#annotation, #children, #head, #parent, #tail

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Node

#annotate, #children?, #consume, #description, #print_hierarchy, #terminate, #transient?, #traverse

Constructor Details

#initialize(reactor, parent = Task.current?, logger: nil, finished: nil, **options, &block) ⇒ Task

Create a new task.

Parameters:

  • reactor (Async::Reactor)

    the reactor this task will run within.

  • parent (Async::Task) (defaults to: Task.current?)

    the parent task.


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# File 'lib/async/task.rb', line 75

def initialize(reactor, parent = Task.current?, logger: nil, finished: nil, **options, &block)
	super(parent || reactor, **options)
	
	@reactor = reactor
	
	@status = :initialized
	@result = nil
	@finished = finished
	
	@logger = logger || @parent.logger
	
	@fiber = make_fiber(&block)
end

Instance Attribute Details

#fiberObject (readonly)


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# File 'lib/async/task.rb', line 112

def fiber
  @fiber
end

#loggerObject (readonly)

Returns the value of attribute logger


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# File 'lib/async/task.rb', line 89

def logger
  @logger
end

#reactorObject (readonly)


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# File 'lib/async/task.rb', line 102

def reactor
  @reactor
end

#statusObject (readonly)


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# File 'lib/async/task.rb', line 119

def status
  @status
end

Class Method Details

.currentAsync::Task

Lookup the Async::Task for the current fiber. Raise `RuntimeError` if none is available.

Returns:

Raises:

  • (RuntimeError)

    if task was not #set! for the current fiber.


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# File 'lib/async/task.rb', line 188

def self.current
	Thread.current[:async_task] or raise RuntimeError, "No async task available!"
end

.current?Async::Task?

Check if there is a task defined for the current fiber.

Returns:


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# File 'lib/async/task.rb', line 194

def self.current?
	Thread.current[:async_task]
end

.yield {|result| ... } ⇒ Object

Yield the unerlying `result` for the task. If the result is an Exception, then that result will be raised an its exception.

Yields:

  • (result)

    result of the task if a block if given.

Returns:

  • (Object)

    result of the task

Raises:

  • (Exception)

    if the result is an exception


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# File 'lib/async/task.rb', line 58

def self.yield
	if block_given?
		result = yield
	else
		result = Fiber.yield
	end
	
	if result.is_a? Exception
		raise result
	else
		return result
	end
end

Instance Method Details

#alive?Boolean

Returns:

  • (Boolean)

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# File 'lib/async/task.rb', line 114

def alive?
	@fiber&.alive?
end

#async(*arguments, **options, &block) ⇒ Object


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# File 'lib/async/task.rb', line 132

def async(*arguments, **options, &block)
	task = Task.new(@reactor, self, **options, &block)
	
	task.run(*arguments)
	
	return task
end

#backtrace(*arguments) ⇒ Object


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# File 'lib/async/task.rb', line 92

def backtrace(*arguments)
	@fiber&.backtrace(*arguments)
end

#complete?Boolean

Returns:

  • (Boolean)

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# File 'lib/async/task.rb', line 226

def complete?
	@status == :complete
end

#current?Boolean

Returns:

  • (Boolean)

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# File 'lib/async/task.rb', line 198

def current?
	self.equal?(Thread.current[:async_task])
end

#failed?Boolean

Returns:

  • (Boolean)

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# File 'lib/async/task.rb', line 214

def failed?
	@status == :failed
end

#finished?Boolean

Whether we can remove this node from the reactor graph.

Returns:

  • (Boolean)

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# File 'lib/async/task.rb', line 210

def finished?
	super && @status != :running
end

#run(*arguments) ⇒ Object

Begin the execution of the task.


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# File 'lib/async/task.rb', line 122

def run(*arguments)
	if @status == :initialized
		@status = :running
		
		@fiber.resume(*arguments)
	else
		raise RuntimeError, "Task already running!"
	end
end

#running?Boolean

Check if the task is running.

Returns:

  • (Boolean)

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# File 'lib/async/task.rb', line 204

def running?
	@status == :running
end

#stop(later = false) ⇒ Object

Stop the task and all of its children.


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# File 'lib/async/task.rb', line 159

def stop(later = false)
	if self.stopped?
		# If we already stopped this task... don't try to stop it again:
		return
	end
	
	if self.running?
		if self.current?
			if later
				@reactor << Stop::Later.new(self)
			else
				raise Stop, "Stopping current task!"
			end
		elsif @fiber&.alive?
			begin
				@fiber.resume(Stop.new)
			rescue FiberError
				@reactor << Stop::Later.new(self)
			end
		end
	else
		# We are not running, but children might be, so transition directly into stopped state:
		stop!
	end
end

#stopped?Boolean

Returns:

  • (Boolean)

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# File 'lib/async/task.rb', line 222

def stopped?
	@status == :stopped
end

#stopping?Boolean

Returns:

  • (Boolean)

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# File 'lib/async/task.rb', line 218

def stopping?
	@status == :stopping
end

#to_sObject


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# File 'lib/async/task.rb', line 97

def to_s
	"\#<#{self.description} (#{@status})>"
end

#waitObject Also known as: result

Retrieve the current result of the task. Will cause the caller to wait until result is available.

Returns:

  • (Object)

    the final expression/result of the task's block.

Raises:

  • (RuntimeError)

    if the task's fiber is the current fiber.


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# File 'lib/async/task.rb', line 143

def wait
	raise RuntimeError, "Cannot wait on own fiber" if Fiber.current.equal?(@fiber)
	
	if running?
		@finished ||= Condition.new
		@finished.wait
	else
		Task.yield{@result}
	end
end

#yieldObject

Yield back to the reactor and allow other fibers to execute.


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# File 'lib/async/task.rb', line 107

def yield
	Task.yield{reactor.yield}
end