The term Continuous Integration (CI) may not have been founded by Martin Fowler, but his article from May 2006 was one reason why this topic became popular. Today, 17 years later, continuous integration is considered a standard and best practice in many software engineering organizations.
The Continuous Integration process commonly starts on every new commit to the main branch or on a new pull request. Conversely, if there is no change to the software repository, the Continuous Integration process does not run. This happens when no one is working on the software project, E.g., on weekends or public holidays, when the project is “feature complete,” or when the focus is on a different initiative.
What is the issue with no CI runs during the “no commit time”?
Today, software is getting more and more complex. Often, this is equal to more and more dependencies. Dependencies in this context are things like external libraries or external services. Those external dependencies can and will break without you noticing it. This may become a shortcoming for the stability of your software. While many of your dependencies might be added explicitly (e.g., a new library), now and then, an implicit, not obvious/visible dependency sneaks in (e.g., a container registry or HTTP calls to external telemetry services).
Running your Continuous Integration process will detect dependency failures early and keep the software buildable.
Common examples of broken dependencies are:
- A library gets deleted from Github or the package registry
- A particular version of a package gets unreleased/deleted due to a security issue
- The container or package registry (npmjs.com, packagist.org, pypi.org, …) is down or is changing APIs/URLs (and reminds you to set up your own mirror)
- You generate data based on an API Call during the CI process, and the API is down
- Your build process sends telemetry data to some service (usage data, build times, …), and the network is failing
You may think, “This is not happening to my software projects”, but if you work in a team, this will happen eventually.
If you don’t run your CI process daily, your software might not be buildable one day due to broken dependencies.
How do you run your CI process daily?
Schedule your CI system to run the CI process daily at a particular time (e.g., 3 am). Nearly all systems have some form of a time trigger:
- Linux with Cron
- Jenkins with the build trigger “Build periodically”
- Github Actions with the
schedulekeyword - Circle CI with Scheduled pipelines
- TeamCity with scheduled Triggers
- Bamboo with Cron-based scheduling
Are there any downsides to this approach?
The usage of computing resources and costs might be one. Depending on how your CI process is designed, this can create additional costs. Imagine you build a cloud-based application that bootstraps 100 nodes in each hyperscale cloud each CI runs. However, this depends on your environment and context. You are the best person to evaluate this.
My engineering tip
Configure a Continuous Integration process run in a regular short interval (e.g., daily) now.