Module: Concurrent::Promises::Resolvable

Includes:
InternalStates
Defined in:
lib/concurrent-ruby-edge/concurrent/edge/promises.rb

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.atomic_resolution(resolvable_map) ⇒ true, false

Resolves all passed events and futures to the given resolutions if possible (all are unresolved) or none.

Parameters:

  • resolvable_map (Hash{Resolvable=>resolve_arguments}, Array<Array(Resolvable, resolve_arguments)>) —

    collection of resolvable events and futures which should be resolved all at once and what should they be resolved to, examples: “‘ruby { a_resolvable_future1 => [true, :val, nil],

    a_resolvable_future2 => [false, nil, :err],
a_resolvable_event => [] }

    “‘

    or

    “‘ruby [[a_resolvable_future1, [true, :val, nil]],

    [a_resolvable_future2, [false, nil, :err]],
[a_resolvable_event, []]]

    “‘

Returns:

  • (true, false) —

    if success



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# File 'lib/concurrent-ruby-edge/concurrent/edge/promises.rb', line 150

def self.atomic_resolution(resolvable_map)
  # atomic_resolution event => [], future => [true, :v, nil]
  sorted = resolvable_map.to_a.sort_by { |resolvable, _| locking_order_by resolvable }

  reserved = 0
  while reserved < sorted.size && sorted[reserved].first.reserve
    reserved += 1
  end

  if reserved == sorted.size
    sorted.each { |resolvable, args| resolvable.resolve(*args, true, true) }
    true
  else
    while reserved > 0
      reserved -= 1
      raise 'has to be reserved' unless sorted[reserved].first.release
    end
    false
  end
end

.locking_order_by(resolvable) ⇒ Comparable

Returns an item to sort the resolvable events or futures by to get the right global locking order of resolvable events or futures.

Returns:

  • (Comparable) —

    an item to sort the resolvable events or futures by to get the right global locking order of resolvable events or futures

See Also:



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# File 'lib/concurrent-ruby-edge/concurrent/edge/promises.rb', line 128

def self.locking_order_by(resolvable)
  resolvable.object_id
end

Instance Method Details

#release ⇒ true, false

Returns on successful release of the reservation.

Returns:

  • (true, false) —

    on successful release of the reservation



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# File 'lib/concurrent-ruby-edge/concurrent/edge/promises.rb', line 121

def release
  compare_and_set_internal_state(RESERVED, PENDING)
end

#reserve ⇒ true, false

Reserves the event or future, if reserved others are prevented from resolving it. Advanced feature. Be careful about the order of reservation to avoid deadlocks, the method blocks if the future or event is already reserved until it is released or resolved.

Examples:

f = Concurrent::Promises.resolvable_future
reserved = f.reserve
Thread.new { f.resolve true, :val, nil } # fails
f.resolve true, :val, nil, true if reserved # must be called only if reserved

Returns:

  • (true, false) —

    on successful reservation



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# File 'lib/concurrent-ruby-edge/concurrent/edge/promises.rb', line 111

def reserve
  while true
    return true if compare_and_set_internal_state(PENDING, RESERVED)
    return false if resolved?
    # FIXME (pitr-ch 17-Jan-2019): sleep until given up or resolved instead of busy wait
    Thread.pass
  end
end