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.



60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
 
# File 'lib/async/task.rb', line 60

def initialize(reactor, parent = Task.current?)
	super(parent || reactor)
	
	@reactor = reactor
	
	@status = :initialized
	@result = nil
	
	@condition = 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: #{$!}")
		rescue Exception => error
			@result = error
			@status = :failed
			# Async.logger.debug("Task #{self} failed: #{$!}")
			raise
		ensure
			# Async.logger.debug("Task #{self} closing: #{$!}")
			finish!
		end
	end
end

Instance Attribute Details

#fiber ⇒ Object (readonly) 



106
107
108
 
# File 'lib/async/task.rb', line 106

def fiber
  @fiber
end

#reactor ⇒ Object (readonly) 



97
98
99
 
# File 'lib/async/task.rb', line 97

def reactor
  @reactor
end

#status ⇒ Object (readonly) 



110
111
112
 
# File 'lib/async/task.rb', line 110

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.



159
160
161
 
# File 'lib/async/task.rb', line 159

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:



165
166
167
 
# File 'lib/async/task.rb', line 165

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



43
44
45
46
47
48
49
50
51
52
53
54
55
 
# 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 



122
123
124
125
126
127
128
 
# File 'lib/async/task.rb', line 122

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) 


177
178
179
 
# File 'lib/async/task.rb', line 177

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.



133
134
135
136
137
138
139
140
141
142
 
# File 'lib/async/task.rb', line 133

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

#run(*args) ⇒ Object

Resume the execution of the task.



113
114
115
116
117
118
119
120
 
# File 'lib/async/task.rb', line 113

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) 


171
172
173
 
# File 'lib/async/task.rb', line 171

def running?
	@status == :running
end

#stop ⇒ void

This method returns an undefined value.

Stop the task and all of its children.



148
149
150
151
152
153
154
 
# File 'lib/async/task.rb', line 148

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

#to_s ⇒ Object 



92
93
94
 
# File 'lib/async/task.rb', line 92

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

#yield ⇒ Object

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



101
102
103
 
# File 'lib/async/task.rb', line 101

def yield
	self.sleep(0)
end