AsyncSourceAsyncIdler

class Idler

A load balancing mechanism that can be used process work when the system is idle.

Definitions

def initialize(maximum_load = 0.8, backoff: 0.01, parent: nil)

  • public

Create a new idler.

Signature

public

Since Async v2.

parameter maximum_load Numeric

The maximum load before we start shedding work.

parameter backoff Numeric

The initial backoff time, used for delaying work.

parameter parent Interface(:async) | Nil

The parent task to use for async operations.

Implementation

def initialize(maximum_load = 0.8, backoff: 0.01, parent: nil)
	@maximum_load = maximum_load
	@backoff = backoff
	@parent = parent
end

def async(*arguments, parent: (@parent or Task.current), **options, &block)

  • asynchronous

Wait until the system is idle, then execute the given block in a new task.

Signature

asynchronous

Executes the given block concurrently.

parameter arguments Array

The arguments to pass to the block.

parameter parent Interface(:async) | Nil

The parent task to use for async operations.

parameter options Hash

The options to pass to the task.

yields {|task| ...}

When the system is idle, the block will be executed in a new task.

Implementation

def async(*arguments, parent: (@parent or Task.current), **options, &block)
	wait
	
	# It is crucial that we optimistically execute the child task, so that we prevent a tight loop invoking this method from consuming all available resources.
	parent.async(*arguments, **options, &block)
end

def wait

Wait until the system is idle, according to the maximum load specified.

If the scheduler is overloaded, this method will sleep for an exponentially increasing amount of time.

Implementation

def wait
	scheduler = Fiber.scheduler
	backoff = nil
	
	while true
		load = scheduler.load
		
		break if load < @maximum_load
		
		if backoff
			sleep(backoff)
			backoff *= 2.0
		else
			scheduler.yield
			backoff = @backoff
		end
	end
end

Discussion