Making Complex Software Fun And Flexible With Plugin Oriented Programming


December 2nd, 2019

1 hr 2 mins 37 secs

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About this Episode


Starting a new project is always exciting because the scope is easy to understand and adding new features is fun and easy. As it grows, the rate of change slows down and the amount of communication necessary to introduce new engineers to the code increases along with the complexity. Thomas Hatch, CTO and creator of SaltStack, didn’t want to accept that as an inevitable fact of software, so he created a new paradigm and a proof-of-concept framework to experiment with it. In this episode he shares his thoughts and findings on the topic of plugin oriented programming as a way to build and scale complex projects while keeping them fun and flexible.


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  • Your host as usual is Tobias Macey and today I’m interviewing Thomas Hatch about his work on the POP library and how he is using plugin oriented programming in his work at SaltStack


  • Introductions
  • How did you get introduced to Python?
  • Can you start by giving your definition of Plugin Oriented Programming and your thoughts on what benefits it provides?
  • You created the POP library as a framework for enabling developers to incorporate this pattern into their own projects. What capabilities does that framework provide and what was your motivation for creating it?
    • How has your work on Salt influenced your thinking on how to implement plugins for software projects?
    • How does POP fit into the future of the SaltStack project?
  • What are some of the advanced patterns or paradigms that the POP model allows for?
  • Can you describe how the POP library itself is implemented and some of the ways that its design has evolved since you first began experimenting with it?
    • What are some of the languages or libraries that you have looked at for inspiration in your design and philosophy around this development pattern?
  • For someone who is building a project on top of POP what does their workflow look like and what are some of the up-front design considerations they should be thinking of?
  • How do you define and validate the contract exposed by or expected from a plugin subsystem?
  • One of the interesting capabilities that you highlight in the documentation is the concept of merging applications. What are your thoughts on the challenges that an engineer might face when merging library or microservice applications built with POP into a single deployable artifact?
    • What would be involved in going the other direction to split a single application into independently runnable microservices?
  • When extracting common functionality from a group of existing applications, what are the relative merits of creating a plugin sybsystem vs writing a library?
  • How does the system design of a POP application impact the available range of communication patterns for software and the teams building it?
  • What are some antipatterns that you anticipate for teams building their projects on top of POP?
  • In the documentation you mention that POP is just an example implementation of the broader pattern and that you hope to see other languages and developer communities adopt it. What are some of the barriers to adoption that you foresee?
  • What are some of the limitations of POP or cases where you would recommend against following this paradigm?
  • What are some of the most interesting, innovative, or unexpected ways that you have seen POP used?
  • What have been some of the most interesting, unexpected, or challenging aspects of building POP?
  • What do you have planned for the future of the POP library, or any applications where you plan to employ this pattern?

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