The Python Podcast.__init__

The Python Podcast.__init__

The podcast about Python and the people who make it great

26 January 2021

Making The Sans I/O Ideal A Reality For The Websockets Library - E299

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Working with network protocols is a common need for software projects, particularly in the current age of the internet. As a result, there are a multitude of libraries that provide interfaces to the various protocols. The problem is that implementing a network protocol properly and handling all of the edge cases is hard, and most of the available libraries are bound to a particular I/O paradigm which prevents them from being widely reused. To address this shortcoming there has been a movement towards "sans I/O" implementations that provide the business logic for a given protocol while remaining agnostic to whether you are using async I/O, Twisted, threads, etc. In this episode Aymeric Augustin shares his experience of refactoring his popular websockets library to be I/O agnostic, including the challenges involved in how to design the interfaces, the benefits it provides in simplifying the tests, and the work needed to add back support for async I/O and other runtimes. This is a great conversation about what is involved in making an ideal a reality.


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  • Your host as usual is Tobias Macey and today I’m interviewing Aymeric Augustin about his work on the websockets library and the work involved in making it sans I/O


  • Introductions
  • How did you get introduced to Python?
  • Can you start by giving an overview of your work on the websockets library and how the project got started?
  • What does "sans I/O" mean and what are the goals associated with it?
  • Can you share the history of your work on the websockets project?
    • What was your motivation for starting down the path of rearchitecting a project that is already production ready?
  • Can you talk through how the websockets library is architected currently?
    • How has the design of the project evolved since you first began working on it?
    • At a high level, what were the changes required to make it functionally sans i/o?
  • What do you see as the primary challenges associated with making network related libraries sans i/o?
  • In your experience of porting websockets to be purely protocol oriented, what are the technical and design challenges that you faced?
  • One of the goals of the Sans I/O approach is to support reusability and composability of network protocol implementations. What has your experience been as to the viability of those goals in practice?
  • What is your current perspective on the cost/benefit of the sans i/o conversion?
  • Who are the primary consumers of the websockets library?
    • How do you foresee the target audience changing once you have completed extracting the protocol logic?
  • What are some of the most interesting, innovative, or unexpected ways that you have seen the websockets project used?
  • What are the most interesting, unexpected, or challenging lessons that you have learned while working on the websockets project and sans i/o conversion?
  • What do you have planned for the future of the project?

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Closing Announcements

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The intro and outro music is from Requiem for a Fish The Freak Fandango Orchestra / CC BY-SA

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