This guide explains how to use
async-container to build basic scalable systems.
Add the gem to your project:
$ bundle add async-container
async-container has several core concepts:
class Async::Container::Threadedare used to manage one or more child processes and threads respectively for parallel execution. While threads share the address space which can reduce overall memory usage, processes have better isolation and fault tolerance.
class Async::Container::Controllermanages one or more containers and handles graceful restarts. Containers should be implemented in such a way that multiple containers can be running at the same time.
A container represents a set of child processes (or threads) which are doing work for you.
require 'async/container' Console.logger.debug! container = Async::Container.new container.async do |task| task.logger.debug "Sleeping..." task.sleep(1) task.logger.debug "Waking up!" end Console.logger.debug "Waiting for container..." container.wait Console.logger.debug "Finished."
The controller provides the life-cycle management for one or more containers of processes. It provides behaviour like starting, restarting, reloading and stopping. You can see some example implementations in Falcon. If the process running the controller receives
SIGHUP it will recreate the container gracefully.
require 'async/container' Console.logger.debug! class Controller < Async::Container::Controller def setup(container) container.async do |task| while true Console.logger.debug("Sleeping...") task.sleep(1) end end end end controller = Controller.new controller.run # If you send SIGHUP to this process, it will recreate the container.
SIGINT is the interrupt signal. The terminal sends it to the foreground process when the user presses ctrl-c. The default behavior is to terminate the process, but it can be caught or ignored. The intention is to provide a mechanism for an orderly, graceful shutdown.
SIGQUIT is the dump core signal. The terminal sends it to the foreground process when the user presses ctrl-\. The default behavior is to terminate the process and dump core, but it can be caught or ignored. The intention is to provide a mechanism for the user to abort the process. You can look at
SIGINT as "user-initiated happy termination" and
SIGQUIT as "user-initiated unhappy termination."
SIGTERM is the termination signal. The default behavior is to terminate the process, but it also can be caught or ignored. The intention is to kill the process, gracefully or not, but to first allow it a chance to cleanup.
SIGKILL is the kill signal. The only behavior is to kill the process, immediately. As the process cannot catch the signal, it cannot cleanup, and thus this is a signal of last resort.
SIGSTOP is the pause signal. The only behavior is to pause the process; the signal cannot be caught or ignored. The shell uses pausing (and its counterpart, resuming via
SIGCONT) to implement job control.
Install a template file into
# my-daemon.service [Unit] Description=My Daemon AssertPathExists=/srv/ [Service] Type=notify WorkingDirectory=/srv/my-daemon ExecStart=bundle exec my-daemon Nice=5 [Install] WantedBy=multi-user.target