Class: Rake::Promise

Inherits:
Object
  • Object
show all
Defined in:
lib/rake/promise.rb

Overview

A Promise object represents a promise to do work (a chore) in the future. The promise is created with a block and a list of arguments for the block. Calling value will return the value of the promised chore.

Used by ThreadPool.

Constant Summary collapse

NOT_SET =

:nodoc: all

Object.new.freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(args, &block) ⇒ Promise

Create a promise to do the chore specified by the block.



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# File 'lib/rake/promise.rb', line 16

def initialize(args, &block)
  @mutex = Mutex.new
  @result = NOT_SET
  @error = NOT_SET
  @args = args.collect { |a| begin; a.dup; rescue; a; end }
  @block = block
end

Instance Attribute Details

#recorder ⇒ Object

:nodoc:



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# File 'lib/rake/promise.rb', line 13

def recorder
  @recorder
end

Instance Method Details

#value ⇒ Object

Return the value of this promise.

If the promised chore is not yet complete, then do the work synchronously. We will wait.



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# File 'lib/rake/promise.rb', line 28

def value
  unless complete?
    stat :sleeping_on, :item_id => object_id
    @mutex.synchronize do
      stat :has_lock_on, :item_id => object_id
      chore
      stat :releasing_lock_on, :item_id => object_id
    end
  end
  error? ? raise(@error) : @result
end

#work ⇒ Object

If no one else is working this promise, go ahead and do the chore.



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# File 'lib/rake/promise.rb', line 41

def work
  stat :attempting_lock_on, :item_id => object_id
  if @mutex.try_lock
    stat :has_lock_on, :item_id => object_id
    chore
    stat :releasing_lock_on, :item_id => object_id
    @mutex.unlock
  else
    stat :bailed_on, :item_id => object_id
  end
end