Class: Async::Reactor

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

Overview

An asynchronous, cooperatively scheduled event reactor.

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, #finished?, #print_hierarchy, #reap, #traverse

Constructor Details

#initialize ⇒ Reactor 



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# File 'lib/async/reactor.rb', line 61

def initialize
  super
  
  @selector = NIO::Selector.new
  @timers = Timers::Group.new
  
  @stopped = true
end

Instance Attribute Details

#stopped ⇒ Object (readonly) 



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

def stopped
  @stopped
end

Class Method Details

.run(*args, &block) ⇒ Object

The preferred method to invoke asynchronous behavior at the top level.

  • When invoked within an existing reactor task, it will run the given block asynchronously. Will return the task once it has been scheduled.
  • When invoked at the top level, will create and run a reactor, and invoke the block as an asynchronous task. Will block until the reactor finishes running.


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# File 'lib/async/reactor.rb', line 45

def self.run(*args, &block)
  if current = Task.current?
    reactor = current.reactor
    
    return reactor.async(*args, &block)
  else
    reactor = self.new
    
    begin
      return reactor.run(*args, &block)
    ensure
      reactor.close
    end
  end
end

Instance Method Details

#async(*args) {|Task| ... } ⇒ Task

Start an asynchronous task within the specified reactor. The task will be executed until the first blocking call, at which point it will yield and and this method will return.

This is the main entry point for scheduling asynchronus tasks.

Yields:

  • (Task) —

    Executed within the asynchronous task.



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# File 'lib/async/reactor.rb', line 87

def async(*args, &block)
  task = Task.new(self, &block)
  
  # I want to take a moment to explain the logic of this.
  # When calling an async block, we deterministically execute it until the
  # first blocking operation. We don't *have* to do this - we could schedule
  # it for later execution, but it's useful to:
  # - Fail at the point of call where possible.
  # - Execute determinstically where possible.
  # - Avoid overhead if no blocking operation is performed.
  task.run(*args)
  
  # Async.logger.debug "Initial execution of task #{fiber} complete (#{result} -> #{fiber.alive?})..."
  return task
end

#close ⇒ void

This method returns an undefined value.

Stop each of the children tasks and close the selector.



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# File 'lib/async/reactor.rb', line 163

def close
  @children.each(&:stop)
  
  # TODO Should we also clear all timers?
  
  @selector.close
  @selector = nil
end

#closed? ⇒ Boolean

Check if the selector has been closed.



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# File 'lib/async/reactor.rb', line 174

def closed?
  @selector.nil?
end

#register(*args) ⇒ Object 



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# File 'lib/async/reactor.rb', line 103

def register(*args)
  monitor = @selector.register(*args)
  
  monitor.value = Fiber.current
  
  return monitor
end

#run(*args, &block) ⇒ Object

Run the reactor until either all tasks complete or #stop is invoked. Proxies arguments to #async immediately before entering the loop.



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

def run(*args, &block)
  raise RuntimeError, 'Reactor has been closed' if @selector.nil?
  
  @stopped = false
  
  # Allow the user to kick of the initial async tasks.
  initial_task = async(*args, &block) if block_given?
  
  @timers.wait do |interval|
    # - nil: no timers
    # - -ve: timers expired already
    # -   0: timers ready to fire
    # - +ve: timers waiting to fire
    interval = 0 if interval && interval < 0
    
    # Async.logger.debug{"[#{self} Pre] Updating #{@children.count} children..."}
    # As timeouts may have been updated, and caused fibers to complete, we should check this.
    
    # If there is nothing to do, then finish:
    # Async.logger.debug{"[#{self}] @children.empty? = #{@children.empty?} && interval #{interval.inspect}"}
    return initial_task if @children.empty? && interval.nil?
    
    # Async.logger.debug{"Selecting with #{@children.count} fibers interval = #{interval.inspect}..."}
    if monitors = @selector.select(interval)
      monitors.each do |monitor|
        if fiber = monitor.value
          fiber.resume # if fiber.alive?
        end
      end
    end
  end until @stopped
  
  return initial_task
ensure
  Async.logger.debug{"[#{self} Ensure] Exiting run-loop (stopped: #{@stopped} exception: #{$!.inspect})..."}
  @stopped = true
end

#sleep(duration) ⇒ Object

Put the calling fiber to sleep for a given ammount of time.



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# File 'lib/async/reactor.rb', line 180

def sleep(duration)
  task = Fiber.current
  
  timer = self.after(duration) do
    if task.alive?
      task.resume
    end
  end
  
  Task.yield
ensure
  timer.cancel if timer
end

#stop ⇒ void

This method returns an undefined value.

Stop the reactor at the earliest convenience. Can be called from a different thread safely.



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# File 'lib/async/reactor.rb', line 113

def stop
  unless @stopped
    @stopped = true
    @selector.wakeup
  end
end

#timeout(duration) ⇒ Object

Invoke the block, but after the timeout, raise TimeoutError in any currenly blocking operation.



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

def timeout(duration)
  backtrace = caller
  task = Fiber.current
  
  timer = self.after(duration) do
    if task.alive?
      error = TimeoutError.new("execution expired")
      error.set_backtrace backtrace
      task.resume error
    end
  end
  
  yield
ensure
  timer.cancel if timer
end

#to_s ⇒ Object 



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# File 'lib/async/reactor.rb', line 70

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