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, #parent

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Node

#annotate, #consume, #description, #print_hierarchy, #reap, #traverse

Constructor Details

#initialize(reactor, parent = Task.current?) ⇒ 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 60

def initialize(reactor, parent = Task.current?)
  super(parent || reactor)
  
  @reactor = reactor
  
  @status = :initialized
  @result = nil
  
  @finished = nil
  
  @fiber = Fiber.new do |*args|
    set!
    
    begin
      @result = yield(self, *args)
      @status = :complete
      # Async.logger.debug("Task #{self} completed normally.")
    rescue Stop
      @status = :stop
      # Async.logger.debug("Task #{self} stopped: #{$!}")
      Async.logger.debug(self) {$!}
    rescue Exception => error
      @result = error
      @status = :failed
      Async.logger.debug(self) {$!}
      raise
    ensure
      # Async.logger.debug("Task #{self} closing: #{$!}")
      finish!
    end
  end
end

Instance Attribute Details

#fiber ⇒ Object (readonly) 



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

def fiber
  @fiber
end

#reactor ⇒ Object (readonly) 



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# File 'lib/async/task.rb', line 98

def reactor
  @reactor
end

#status ⇒ Object (readonly) 



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# File 'lib/async/task.rb', line 111

def status
  @status
end

Class Method Details

.current ⇒ Async::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 160

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 166

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 43

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

#async(*args, &block) ⇒ Object 



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# File 'lib/async/task.rb', line 123

def async(*args, &block)
  task = Task.new(@reactor, self, &block)
  
  task.run(*args)
  
  return task
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 178

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

#result ⇒ Object Also known as: wait

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

Returns:

  • (Object)

Raises:

  • (RuntimeError) —

    if the task's fiber is the current fiber.



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# File 'lib/async/task.rb', line 134

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

#run(*args) ⇒ Object

Resume the execution of the task.



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

def run(*args)
  if @status == :initialized
    @status = :running
    @fiber.resume(*args)
  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 172

def running?
  @status == :running
end

#stop ⇒ void

This method returns an undefined value.

Stop the task and all of its children.



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# File 'lib/async/task.rb', line 149

def stop
  @children.each(&:stop)
  
  if @fiber.alive?
    @fiber.resume(Stop.new)
  end
end

#to_s ⇒ Object 



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# File 'lib/async/task.rb', line 93

def to_s
  "<#{self.description} status=#{@status}>"
end

#yield ⇒ Object

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



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

def yield
  reactor.yield
end