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Cotyledon provides a framework for defining long-running services.

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Cotyledon provides a framework for defining long-running services.

It provides handling of Unix signals, spawning of workers, supervision of children processes, daemon reloading, sd-notify, rate limiting for worker spawning, and more.

Why Cotyledon

This library is mainly used in Openstack Telemetry projects for now. In the past oslo.service was used. But our projects don’t want to use eventlet anymore.

oslo.service is written on top of eventlet to provide two main features:

  • periodic tasks
  • workers processes management

The first one was replaced by another Oslo lib called futurist and the second part by Cotyledon.

Our main issue was greenlet that doesn’t run in timely fashion because we don’t monkeypatch the python stdlib anymore. Making Tooz/Oslo.messaging hearbeats to fail. And processes that doesn’t exists as expected due to greenpipe never processed.

Unlike oslo.service, cotyledon have:

  • The same code path when workers=1 and workers>=2
  • Reload API (on SIGHUP) hooks work in case of you don’t want to restarting children
  • A separated API for children process termination and for master process termination
  • Seatbelt to ensure only one service workers manager run at a time.
  • Is signal concurrency safe.
  • Support non posix platform, because it’s built on top of multiprocessing module instead of os.fork
  • Provide functional testing

And doesn’t:

  • facilitate the creation of wsgi application (sockets sharing between parent and children process). Because too many wsgi webserver already exists.

So these toohard to fix issues and the heavy eventlet dependencies make this library to appear.

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