GitHub Actions CI first impressions

[Zoltán Nagy]

I finally got access to the GH Actions CI beta. Tried it out on my fork of the main Zipkin repo. I've translated the testing* (but not the release) part of the current Travis setup. The successful build and test is https://github.com/abesto/zipkin/commit/d3dc93b75a6fa3dc169aa661221d21abe881b363/checks. The workflow definition is at https://github.com/abesto/zipkin/blob/master/.github/workflows/maven.yml.

* so I'm not running `publish.sh` at all. Maybe it also does some extra testing? Either way, that difference shouldn't affect most of these conclusions I think.

Initial impressions follow.

• Initial setup was surprisingly painless. The full process from "let's try it" to "test passed" took about 30 minutes (!!!). You create a YAML file under .github/workflows (AFAICT you can have any number of workflows that can be triggered in parallel if that makes sense for a project)
• The syntax / structure is pretty close to Travis, but:
• The Docker "service" is always enabled. By default you run on the host, but can also tell GH to instead run the whole thing inside a container (and configure that container)
• There are no built-in "services", but you can configure any number of auxiliary Docker containers as you like
• `sudo` works on the host
• There are a ton of built-in "steps" published via the GitHub Actions Marketplace. There are basic ones like "install JDK" (which I used) but also super fancy ones like "do a vuln scan on my Java codebase" (which I did not use). Check it out: https://github.com/marketplace?type=actions
• The current "set up JDK" step supports only Zulu, but there's active work on making it support OpenJDK as well (and default to it, actually)
  
• There's support for configuring what kind of events trigger the workflow (like "commits on branches matching this regex"). The full workflow definition reference is at https://help.github.com/en/articles/workflow-syntax-for-github-actions.
• Negative matches are supported, so we can translate our "only on non-release branches" condition from the Travis job
• There is currently no support for caching intermediate build artifacts or dependency caches (don't know if this is planned or not)
• There's support for secrets, which are edited via the Settings page of the repository, and can be read from the workflow.

Overall, this looks pretty promising: it seems that mostly there is feature parity with Travis (for our purposes at least), and my experience has been roughly the same level of delightful as with Travis. I strictly prefer the secret management solution of GH Actions to the solution in Travis. The build log viewer UI is a bit on the rough side, but functional.

At this point I'd recommend we keep a close eye on GH CI. If (and this is a big if) GH Actions CI brings bigger limits, or more stability than Travis, then there might be a strong case for switching to it from Travis. There might also be something to say for cool GH integrations, though I'm not exactly sure what that would actually mean.

My overall conclusion is a cautious "looks good, let's see where it goes and maybe do some PoCs / experiments after GA".

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Zoltán Nagy
https://abesto.net

[Zoltán Nagy]

On second thought: step / action definitions (like "set up JDK") can also come from public GH repositories or Docker images. This might possibly provide a way to DRY the testing / release processes across our many repositories. I haven't investigated whether this is actually feasible (or to what extent), but it is at least an interesting possibility.

[Adrian Cole]

I've forwarded this to Ray and Rag, who I'm not sure are on this list.
Looks promising and timely as I know we are now having more
workflow-related works in progress. Thanks for capturing the
investigation so far, Zoltán!

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