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) 



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

def fiber
  @fiber
end

#reactor ⇒ Object (readonly) 



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

def reactor
  @reactor
end

#status ⇒ Object (readonly) 



105
106
107
 
# File 'lib/async/task.rb', line 105

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.



154
155
156
 
# File 'lib/async/task.rb', line 154

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:



160
161
162
 
# File 'lib/async/task.rb', line 160

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 



117
118
119
120
121
122
123
 
# File 'lib/async/task.rb', line 117

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) 


172
173
174
 
# File 'lib/async/task.rb', line 172

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.



128
129
130
131
132
133
134
135
136
137
 
# File 'lib/async/task.rb', line 128

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.



108
109
110
111
112
113
114
115
 
# File 'lib/async/task.rb', line 108

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) 


166
167
168
 
# File 'lib/async/task.rb', line 166

def running?
  @status == :running
end

#stop ⇒ void

This method returns an undefined value.

Stop the task and all of its children.



143
144
145
146
147
148
149
 
# File 'lib/async/task.rb', line 143

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