Building Open Source Projects
This document provides tips and best practices for building your open source project on CircleCI in the following sections:
To support the open source community, organizations on Github or Bitbucket will be given 100,000 free credits per week that can be spent on open source projects. These credits can be spent on Linux-medium resources. Each organization can have a maximum of four concurrent jobs running.
Note: If you are building an open source project on macOS, contact email@example.com to enable these additional containers.
Note: There is a concurrency limit of 4 containers for Docker and Machine executors whereas macOS executors are limited to 1 container. Additional containers will be queued.
While open source can be a liberating practice, take care not to liberate sensitive information.
- If your repository is public, your CircleCI project and its build logs are also public. Pay attention to the information you choose to print.
- Environment variables set in the CircleCI application are hidden from the public, these variables will not be shared in forked PRs unless explicitly enabled.
Features and settings for open source projects
The following features and settings are especially useful for open source projects.
Private environment variables
Many projects require API tokens, SSH keys, or passwords. Private environment variables allow you to safely store secrets, even if your project is public.
For more information, see the Environment Variables document.
Only build pull requests
By default, CircleCI builds every commit from every branch. This behavior may be too aggressive for open source projects, which often have significantly more commits than private projects.
To change this setting, go to the Project Settings>Advanced of your project and set the Only build pull requests option to On.
Note: Even if this option is enabled, CircleCI will still build all commits from your project’s default branch and tags
Build pull requests from forked repositories
Many open source projects accept PRs from forked repositories. Building these PRs is an effective way to catch bugs before manually reviewing changes.
By default, CircleCI does not build PRs from forked repositories. To change this setting, go to the Project Settings>Advanced of your project and set the Build forked pull requests option to On.
NoteThis feature is not currently supported for BitBucket users.
Note: If a user submits a pull request to your repository from a fork, but no pipeline is triggered, then the user most likely is following a project fork on their personal account rather than the project itself of CircleCi, causing the jobs to trigger under the user’s personal account and not the organization account. To resolve this issue, have the user unfollow their fork of the project on CircleCI and instead follow the source project. This will trigger their jobs to run under the organization when they submit pull requests.
Pass secrets to builds from forked pull requests
Running an unrestricted build in a parent repository can be dangerous. Projects often contain sensitive information, and this information is freely available to anyone who can push code that triggers a build.
By default, CircleCI does not pass secrets to builds from forked PRs for open source projects and hides four types of configuration data:
Environment variables set through the application.
Passphraseless private SSH keys you have added to CircleCI to access arbitrary hosts during a build.
AWS permissions and configuration files.
Note: Forked PR builds of open source projects that require secrets will not run successfully on CircleCI until you enable this setting.
If you are comfortable sharing secrets with anyone who forks your project and opens a PR, you can enable the Pass secrets to builds from forked pull requests option. In the Project Settings>Advanced of your project, set the Pass secrets to builds from forked pull requests option to On.
Caches are isolated based on GitHub Repo for PRs. CircleCI uses the GitHub repository-id of the originator of the fork PR to identify the cache.
- PRs from the same fork repo will share a cache (this includes, as previously stated, that PRs in the master repo share a cache with master).
- Two PRs in different Fork Repos will have different caches.
- enabling the sharing of environment variables will enable cache sharing between the original repo and all forked builds.
Currently there is no pre-population of caches because this optimization hasn’t made it to the top of the priority list yet.
Example open source projects
Following are a few examples of projects (big and small) that build on CircleCI:
- StoryBook - Interactive UI component dev & test: React, React Native, Vue, Angular, Ember.
- Angular - Framework for building browser and desktop web applications.
- Apollo - A community building flexible open source tools for GraphQL.
- PyTorch - Data manipulation and Machine Learning platform.
- Calypso - The next generation webapp powering WordPress.com.
- Fastlane - A build automatically tool for Android and iOS.
- Yarn - The npm replacement.
Refer to the Examples document for more public and open source project configuration links organized by CircleCI features and by programming language.