GitHub Actions vs Jenkins: where StarSling fits

Jenkins is "a self-contained, open source automation server". You install and run it yourself, through native system packages, Docker, or as a standalone application on any machine with a Java Runtime Environment. The controller is the Jenkins service itself: a web server that handles configuration, authorization and authentication, and acts as the "brain" deciding how, when and where to run tasks.

GitHub Actions is part of GitHub. Jobs run on runners: GitHub-hosted runners are virtual machines where "machine maintenance and upgrades are taken care of for you", and self-hosted runners are systems you deploy and manage. StarSling runners join that list as managed runners: install the StarSling GitHub App and set runs-on to starsling-ubuntu-24.04.

A Jenkins Pipeline is written into a text file called a Jenkinsfile and committed to the project's repository, so the pipeline is versioned and reviewed like any other code. A Jenkinsfile uses Declarative or Scripted syntax. Declarative Pipeline is designed to make pipeline code easier to write and read; Scripted Pipeline is a general-purpose DSL built with Groovy that runs from the top of the file downwards.

A GitHub Actions workflow is a YAML file in .github/workflows. It runs when an event in the repository triggers it, on a schedule, or manually, and each job runs its steps on a runner. GitHub's Jenkins migration guide pairs the two models: Jenkins stages become jobs, and the agent directive becomes runs-on.

Plugins are "the primary means of enhancing the functionality of a Jenkins environment", and the Jenkins docs count over a thousand of them. They are installed on the controller through the Plugin Manager or the Jenkins CLI, downloaded with their dependencies from the Update Center that the Jenkins project operates. Pipeline code shared across projects lives in Shared Libraries, defined in their own source repositories and loaded into existing Pipelines.

In GitHub Actions the reuse unit is an action, referenced with uses: from the same repository, any public repository, or a published Docker image, and browsable in GitHub Marketplace from the workflow editor. Actions are Docker container, JavaScript or composite actions, and reusable workflows share whole jobs between workflows. Workflows on StarSling runners use the same actions.

Jenkins runs builds on agents: small Java client processes that connect to the controller and run tasks through executors on the nodes you provide. Agents can be statically allocated or provisioned through Kubernetes, OpenShift, Amazon EC2, Azure, Google Cloud and other cloud providers. Build tools are installed on each node, directly or in a container, and each node's executor count sets how many tasks it runs at once. The Jenkins security docs advise running builds on agents and keeping them off the built-in node.

A self-hosted GitHub Actions runner carries the same kind of ownership: you are responsible for updating its operating system and software. GitHub-hosted runners and StarSling runners are managed for you. A job runs on StarSling when its runs-on label is starsling-ubuntu-24.04, and StarSling's agents read the workflow, logs and telemetry and open pull requests that improve caching, installs and test execution.

GitHub's Jenkins migration guide maps Declarative Pipeline onto workflow syntax: agent to runs-on, stages to jobs, steps to steps, environment to env, triggers to on, Jenkins cron syntax to on.schedule, and when to if. GitHub Actions Importer automates the conversion: a GitHub CLI extension whose audit, forecast, dry-run and migrate commands plan the move, preview a workflow, and open it as a pull request.

• Inventory each pipeline's Jenkinsfile, plugins, Shared Libraries and the agent labels its stages run on.
• Run gh actions-importer audit jenkins, then dry-run on a representative pipeline, then migrate to open the workflow as a pull request.
• Map each plugin to a Marketplace action or a run: step, and each agent label to a runs-on label.
• Set runs-on: starsling-ubuntu-24.04 on Ubuntu jobs to run them on StarSling, and keep the Jenkins job running in parallel until the workflow's checks pass.

Once the pipeline is a GitHub Actions workflow, StarSling's agents open reviewable pull requests that apply the GitHub Actions CI best practices to it. Read the public Mastra optimization PRs and results and the Better Auth case study to see those changes on real workflows.

For new accounts, AI-powered optimization PRs are only available to customers on paid plans and are not enabled by default.