Class: Async::Container::Forked::Child

Inherits:
Channel
  • Object
show all
Defined in:
lib/async/container/forked.rb

Overview

Represents a running child process from the point of view of the parent container.

Defined Under Namespace

Classes: Instance

Instance Attribute Summary collapse

Attributes inherited from Channel

#in, #out

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Channel

#close_read, #close_write, #receive

Constructor Details

#initialize(name: nil, **options) ⇒ Child

Initialize the process.



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# File 'lib/async/container/forked.rb', line 144

def initialize(name: nil, **options)
	super(**options)
	
	@name = name
	@status = nil
	@pid = nil
	
	@pid = yield(self)
	
	# The parent process won't be writing to the channel:
	self.close_write
end

Instance Attribute Details

#name ⇒ Object

The name of the process.



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# File 'lib/async/container/forked.rb', line 186

def name
  @name
end

#pid ⇒ Object (readonly)

Returns the value of attribute pid.



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# File 'lib/async/container/forked.rb', line 189

def pid
  @pid
end

#The process identifier.(processidentifier.) ⇒ Object (readonly) 



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# File 'lib/async/container/forked.rb', line 189

attr :pid

Class Method Details

.fork(**options) ⇒ Object

Fork a child process appropriate for a container.



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# File 'lib/async/container/forked.rb', line 101

def self.fork(**options)
	# $stderr.puts fork: caller
	self.new(**options) do |process|
		# CRuby makes the currently executing fiber the root fiber in the child process and clears its resuming fiber, so the caller's stack can be collected without forking from a separate native thread:
		::Fiber.new(blocking: true) do
			::Process.fork do
				# We use `Thread.current.raise(...)` so that exceptions are filtered through `Thread.handle_interrupt` correctly.
				Signal.trap(:INT){::Thread.current.raise(Interrupt)}
				Signal.trap(:TERM){::Thread.current.raise(Interrupt)}  # Same as SIGINT.
				Signal.trap(:HUP){::Thread.current.raise(Restart)}
				
				# This could be a configuration option:
				::Thread.handle_interrupt(SignalException => :immediate) do
					yield Instance.for(process)
				rescue Interrupt
					# Graceful exit.
				rescue Exception => error
					Console.error(self, error)
					
					exit!(1)
				end
			end
		end.resume
	end
end

.spawn(*arguments, name: nil, **options) ⇒ Object

Spawn a child process using Process.spawn.

The child process will need to inform the parent process that it is ready using a notification protocol.



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# File 'lib/async/container/forked.rb', line 134

def self.spawn(*arguments, name: nil, **options)
	self.new(name: name) do |process|
		Notify::Pipe.new(process.out).before_spawn(arguments, options)
		
		::Process.spawn(*arguments, **options)
	end
end

Instance Method Details

#as_json ⇒ Object

Convert the child process to a hash, suitable for serialization.



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# File 'lib/async/container/forked.rb', line 160

def as_json(...)
	{
		name: @name,
		pid: @pid,
		status: @status&.to_i,
	}
end

#close ⇒ Object

Invoke #terminate! and then #wait for the child process to exit.



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# File 'lib/async/container/forked.rb', line 201

def close
	self.terminate!
	self.wait
ensure
	super
end

#inspect ⇒ Object Also known as: to_s

A human readable representation of the process.



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# File 'lib/async/container/forked.rb', line 193

def inspect
	"\#<#{self.class} name=#{@name.inspect} status=#{@status.inspect} pid=#{@pid.inspect}>"
end

#interrupt! ⇒ Object

Send SIGINT to the child process.



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# File 'lib/async/container/forked.rb', line 209

def interrupt!
	unless @status
		::Process.kill(:INT, @pid)
	end
end

#kill! ⇒ Object

Send SIGKILL to the child process.



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# File 'lib/async/container/forked.rb', line 223

def kill!
	unless @status
		::Process.kill(:KILL, @pid)
	end
end

#restart! ⇒ Object

Send SIGHUP to the child process.



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# File 'lib/async/container/forked.rb', line 230

def restart!
	unless @status
		::Process.kill(:HUP, @pid)
	end
end

#terminate! ⇒ Object

Send SIGTERM to the child process.



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# File 'lib/async/container/forked.rb', line 216

def terminate!
	unless @status
		::Process.kill(:TERM, @pid)
	end
end

#to_json ⇒ Object

Convert the request to JSON.



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# File 'lib/async/container/forked.rb', line 171

def to_json(...)
	as_json.to_json(...)
end

#wait(timeout = 0.1) ⇒ Object

Wait for the child process to exit.



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# File 'lib/async/container/forked.rb', line 241

def wait(timeout = 0.1)
	if @pid && @status.nil?
		Console.debug(self, "Waiting for process to exit...", child: {process_id: @pid}, timeout: timeout)
		
		_, @status = ::Process.wait2(@pid, ::Process::WNOHANG)
		
		if @status.nil?
			sleep(timeout) if timeout
			
			_, @status = ::Process.wait2(@pid, ::Process::WNOHANG)
			
			if @status.nil?
				Console.warn(self, "Process is blocking, sending kill signal...", child: {process_id: @pid}, timeout: timeout)
				self.kill!
				
				# Wait for the process to exit:
				_, @status = ::Process.wait2(@pid)
			end
		end
	end
	
	Console.debug(self, "Process exited.", child: {process_id: @pid, status: @status})
	
	return @status
end