class Scheduler

public

Since Async v1.

def self.supported?
	true
end

public

Since Async v1.

parameter　parent　Node | Nil

The parent node to use for task hierarchy.

parameter　selector　IO::Event::Selector

The selector to use for event handling.

def initialize(parent = nil, selector: nil)
	super(parent)
	
	@selector = selector || ::IO::Event::Selector.new(Fiber.current)
	@interrupted = false
	
	@blocked = 0
	
	@busy_time = 0.0
	@idle_time = 0.0
	
	@timers = ::IO::Event::Timers.new
end

returns　Float

The load of the scheduler. 0.0 means no load, 1.0 means fully loaded or over-loaded.

def load
	total_time = @busy_time + @idle_time
	
	# If the total time is zero, then the load is zero:
	return 0.0 if total_time.zero?
	
	# We normalize to a 1 second window:
	if total_time > 1.0
		ratio = 1.0 / total_time
		@busy_time *= ratio
		@idle_time *= ratio
		
		# We don't need to divide here as we've already normalised it to a 1s window:
		return @busy_time
	else
		return @busy_time / total_time
	end
end

def scheduler_close(error = $!)
	# If the execution context (thread) was handling an exception, we want to exit as quickly as possible:
	unless error
		self.run
	end
ensure
	self.close
end

def terminate
	# If that doesn't work, take more serious action:
	@children&.each do |child|
		child.terminate
	end
	
	return @children.nil?
end

public

Since Async v1.

def close
	self.run_loop do
		until self.terminate
			self.run_once!
		end
	end
	
	Kernel.raise "Closing scheduler with blocked operations!" if @blocked > 0
ensure
	# We want `@selector = nil` to be a visible side effect from this point forward, specifically in `#interrupt` and `#unblock`. If the selector is closed, then we don't want to push any fibers to it.
	selector = @selector
	@selector = nil
	
	selector&.close
	
	consume
end

returns　Boolean

Whether the scheduler has been closed.

public

Since Async v1.

def closed?
	@selector.nil?
end

returns　String

A description of the scheduler.

def to_s
	"\#<#{self.description} #{@children&.size || 0} children (#{stopped? ? 'stopped' : 'running'})>"
end

asynchronous

May be called from any thread.

def interrupt
	@interrupted = true
	@selector&.wakeup
end

def transfer
	@selector.transfer
end

def yield
	@selector.yield
end

parameter　fiber　Fiber | Object

The object to be resumed on the next iteration of the run-loop.

def push(fiber)
	@selector.push(fiber)
end

parameter　fiber　Fiber

The fiber to raise the exception on.

parameter　*arguments　Array

The arguments to pass to the fiber.

def raise(...)
	@selector.raise(...)
end

parameter　fiber　Fiber

The fiber to resume.

parameter　arguments　Array

The arguments to pass to the fiber.

def resume(fiber, *arguments)
	@selector.resume(fiber, *arguments)
end

asynchronous

May only be called on same thread as fiber scheduler.

def block(blocker, timeout)
	# $stderr.puts "block(#{blocker}, #{Fiber.current}, #{timeout})"
	fiber = Fiber.current
	
	if timeout
		timer = @timers.after(timeout) do
			if fiber.alive?
				fiber.transfer(false)
			end
		end
	end
	
	begin
		@blocked += 1
		@selector.transfer
	ensure
		@blocked -= 1
	end
ensure
	timer&.cancel!
end

public

Since Async v2 and Ruby v3.1.

asynchronous

May be called from any thread.

parameter　blocker　Object

The object that was blocking the fiber.

parameter　fiber　Fiber

The fiber to unblock.

def unblock(blocker, fiber)
	# $stderr.puts "unblock(#{blocker}, #{fiber})"
	
	# This operation is protected by the GVL:
	if selector = @selector
		selector.push(fiber)
		selector.wakeup
	end
end

public

Since Async v2 and Ruby v3.1.

asynchronous

May be non-blocking.

parameter　duration　Numeric | Nil

The time in seconds to sleep, or if nil, indefinitely.

def kernel_sleep(duration = nil)
	if duration
		self.block(nil, duration)
	else
		self.transfer
	end
end

public

Since Async v2.

asynchronous

May be non-blocking.

parameter　hostname　String

The hostname to resolve.

def address_resolve(hostname)
	# On some platforms, hostnames may contain a device-specific suffix (e.g. %en0). We need to strip this before resolving.
	# See <https://github.com/socketry/async/issues/180> for more details.
	hostname = hostname.split("%", 2).first
	::Resolv.getaddresses(hostname)
end

public

Since Async v2.

asynchronous

May be non-blocking.

parameter　io　IO

The IO object to wait on.

parameter　events　Integer

The events to wait for, e.g. IO::READABLE, IO::WRITABLE, etc.

parameter　timeout　Float | Nil

The maximum time to wait, or if nil, indefinitely.

def io_wait(io, events, timeout = nil)
	fiber = Fiber.current
	
	if timeout
		# If an explicit timeout is specified, we expect that the user will handle it themselves:
		timer = @timers.after(timeout) do
			fiber.transfer
		end
	elsif timeout = get_timeout(io)
		# Otherwise, if we default to the io's timeout, we raise an exception:
		timer = @timers.after(timeout) do
			fiber.raise(::IO::TimeoutError, "Timeout (#{timeout}s) while waiting for IO to become ready!")
		end
	end
	
	return @selector.io_wait(fiber, io, events)
ensure
	timer&.cancel!
end

public

Since Async v2 and Ruby with IO::Buffer support.

asynchronous

May be non-blocking.

parameter　io　IO

The IO object to read from.

parameter　buffer　IO::Buffer

The buffer to read into.

parameter　length　Integer

The minimum number of bytes to read.

parameter　offset　Integer

The offset within the buffer to read into.

def io_read(io, buffer, length, offset = 0)
	fiber = Fiber.current
	
	if timeout = get_timeout(io)
		timer = @timers.after(timeout) do
			fiber.raise(::IO::TimeoutError, "Timeout (#{timeout}s) while waiting for IO to become readable!")
		end
	end
	
	@selector.io_read(fiber, io, buffer, length, offset)
ensure
	timer&.cancel!
end

public

Since Async v2 and Ruby v3.3.1 with IO::Buffer support.

asynchronous

May be non-blocking.

parameter　io　IO

The IO object to write to.

parameter　buffer　IO::Buffer

The buffer to write from.

parameter　length　Integer

The minimum number of bytes to write.

parameter　offset　Integer

The offset within the buffer to write from.

def io_write(io, buffer, length, offset = 0)
	fiber = Fiber.current
	
	if timeout = get_timeout(io)
		timer = @timers.after(timeout) do
			fiber.raise(::IO::TimeoutError, "Timeout (#{timeout}s) while waiting for IO to become writable!")
		end
	end
	
	@selector.io_write(fiber, io, buffer, length, offset)
ensure
	timer&.cancel!
end

public

Since Async v2.

asynchronous

May be non-blocking.

parameter　pid　Integer

The process ID to wait for.

parameter　flags　Integer

A bit-mask of flags suitable for Process::Status.wait.

returns　Process::Status

A process status instance.

asynchronous

May be non-blocking..

def process_wait(pid, flags)
	return @selector.process_wait(Fiber.current, pid, flags)
end

public

Since Async v2.19 and Ruby v3.4.

asynchronous

May be non-blocking.

parameter　work　Proc

The work to execute on a background thread.

returns　Object

The result of the work.

def blocking_operation_wait(work)
	thread = Thread.new(&work)
	
	result = thread.join
	
	thread = nil
	
	return result
ensure
	thread&.kill
end

public

Since Async v1.

asynchronous

Must be invoked from blocking (root) fiber.

parameter　timeout　Float | Nil

The maximum timeout, or if nil, indefinite.

returns　Boolean

Whether there is more work to do.

def run_once(timeout = nil)
	Kernel.raise "Running scheduler on non-blocking fiber!" unless Fiber.blocking?
	
	if self.finished?
		self.stop
	end
	
	# If we are finished, we stop the task tree and exit:
	if @children.nil?
		return false
	end
	
	return run_once!(timeout)
end

public

Since Async v1.

def stop
	@children&.each do |child|
		child.stop
	end
end

public

Since Async v1.

yields　{|task| ...}

The top level task, if a block is given.

returns　Task

The initial task that was scheduled into the reactor.

def run(...)
	Kernel.raise ClosedError if @selector.nil?
	
	initial_task = self.async(...) if block_given?
	
	self.run_loop do
		run_once
	end
	
	return initial_task
end

public

Since Async v1.

asynchronous

May context switch immediately to new task.

deprecated

Use #run or Async::Task#async instead.

yields　{|task| ...}

Executed within the task.

returns　Task

The task that was scheduled into the reactor.

def async(*arguments, **options, &block)
	# warn "Async::Scheduler#async is deprecated. Use `run` or `Task#async` instead.", uplevel: 1, category: :deprecated
	
	Kernel.raise ClosedError if @selector.nil?
	
	task = Task.new(Task.current? || self, **options, &block)
	
	task.run(*arguments)
	
	return task
end

public

Since Async v1.

asynchronous

May raise an exception at any interruption point (e.g. blocking operations).

parameter　duration　Numeric

The time in seconds, in which the task should complete.

parameter　exception　Class

The exception class to raise.

parameter　message　String

The message to pass to the exception.

yields　{|duration| ...}

The block to execute with a timeout.

def with_timeout(duration, exception = TimeoutError, message = "execution expired", &block)
	fiber = Fiber.current
	
	timer = @timers.after(duration) do
		if fiber.alive?
			fiber.raise(exception, message)
		end
	end
	
	yield timer
ensure
	timer&.cancel!
end

public

Since Async v1 and Ruby v3.1. May be invoked from Timeout.timeout.

asynchronous

May raise an exception at any interruption point (e.g. blocking operations).

parameter　duration　Numeric

The time in seconds, in which the task should complete.

parameter　exception　Class

The exception class to raise.

parameter　message　String

The message to pass to the exception.

yields　{|duration| ...}

The block to execute with a timeout.

def timeout_after(duration, exception, message, &block)
	with_timeout(duration, exception, message) do |timer|
		yield duration
	end
end