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Introducing ppacer: yet another DAG scheduler which I prefer

Apr 18, 2024

Intro

As I mentioned in New Scheduler, in the second half of 2023 I started working on implementing new scheduler in Go. In this post I wanted to share with you the current status of the project, next steps and few links.

The name: ppacer

At the end of the previous year I was already working already for 4-5 months on this project but still I didn’t have a name for it. On my local disk it lived in gosched catalog for those couple of months. It was to this point, that I even setup a goal for 2024, to come up with a name for the project.

Around mid January 2024 I finally came up with the name - ppacer. The part ‘pacer’ comes from running. In marathons or other races a pacer is a runner who helps to set the pace for other runners. The initial “p” comes from a word “process”. So it’s a loose analogy to something that sets the pace for your processes. At the same time it uses the same name convention as other famous tool - pprof, which I think sounds really good.

There it is, I have the name! I was really happy. That enabled me to buy a domain and create an organization on GitHub.

Current status

At the moment ppacer is a set of Go libraries which can be used, to define and build a DAG which would run on a schedule, a scheduler and an executor. All those components can be compiled into single statically linked binary, or there might be single scheduler program and multiple executors placed on separate machines. Anyway, very basic version of the backend is ready. It doesn’t yet have MPV coverage regarding features, but it’s good enough to be used in some setups.

Currently I’m using ppacer to do backups of my Home Database and refresh TLS certificates for my applications.

There is no frontend yet at all. If you’re fine with checking logs or DAG runs information in SQLite or any other Go sql-compatible database, feel free to play with it.

There are few links you might be interested in, if this project sounds interesting to you. There is github.com/ppacer organization on GitHub. There you can find

Standard Go packages documentation (API reference) can be found in here:

Last but not least, ppacer main page for high-level documentation, examples and other information is here:

Documentation

As I mentioned ppacer backed is working for arbitrary minimal set of selected features. I’d like to focus now on the frontend part, but before I do, I decided to write down a bit of documentation. One part is Go libraries public API documentation. That was mostly written during the development, so it needed to be just polished a bit. The other part is documenting high-level design, instructions on how to use ppacer, how to extend it, how to implement your own schedules and so on.

There are few reasons why I want to do it. One is to show potential users or interested developers how to even start and run “hello world” example. The other reason is for me in the future, when I’ll be back from frontend development, to remember what I was thinking months ago and why I choose to implement it this and not the other way. Another reason was a bit surprising. Writing down documentation helped me a lot, to make libraries API better and more consistent. Being a single developer on the project should already give a lot of consistency but even in this case I saw small differences in naming or conventions over the time. Writing it down in documentation helped me see it. I wish I had done it earlier in the project.

A friend recommended me Astro starlight, to build documentation web page. It’s great! It’s really easy to setup, it’s rather flexible and looks gorgeous in my opinion - lean, fast and modern.

Next steps

The next steps for the project are as follows:

  1. Finish writing documentation for existing backend
  2. Start working on frontend PoC (probably HTMX + tmpl)
  3. Design the logo
  4. Write first version of ppacer frontend
  5. Go back to add few more features on the backed
  6. Prepare ppacer MVP version
  7. …
  8. Profit?

Summary

That’s it for now. It’s not really yet “introducing ppacer” it’s rather introducing the name and give you the current status, but hey I liked that title. By the way the title of this post was inspired by Maxwell calling his work on theory of electromagnetism “another theory of electricity which I prefer”. You can read about this very interesting story in this essay.

If you’re interested in the project already, you can find the “hello world” example in here: ppacer.org/start/intro/.

References

  1. Why is Maxwell’s Theory so hard to understand?