Common Concourse Pipelines

Reusable Concourse pipelines. Reference the pipeline for your app's language, fly set-pipeline, and you're done.

Index

• ci: Concrete pipeline instances that use templates from this repository.
• container: Template pipelines for containerized software.
• go: Template pipeline for Go apps. Not currently in use.

Usage

See the README in each folder for pipeline-specific details. In general, you will "register" a new pipeline by modifying a parent pipeline in ci/ and configuring it with a vars file. Once you merge your changes to main, the parent pipeline will automatically create your new child pipeline.

Motivation

An adage of Continuous Integration: "Treat pipelines like cattle, not like pets."

cloud.gov maintains a variety of software written in a handful of programming languages. Apps written in the same language should be built and deployed in the same way, and developers should not have to reinvent the wheel by writing a new pipeline every time.

Architecture

Common pipelines use a parent/child pattern so that one pipeline can manage many others. For example, this diagram shows the relationships between container pipelines:

flowchart LR
    classDef ellipses fill:#ffffff,stroke:#ffffff
    classDef job fill:#ecffec,stroke:#73d893

    subgraph Main Concourse Team
        container["container pipeline"]
        container -->|sets self| container
        container -->|contains| external["set-external-pipelines job"]:::job
        container -->|contains| internal["set-internal-pipelines job"]:::job
        container -->|contains| pages["set-pages-pipelines job"]:::job

        external -->|sets| cf-cli-resource["cf-cli-resource pipeline"]
        external -->|sets| cf-resource["cf-resource pipeline"]
        external -->|sets| external-etc["..."]:::ellipses
        external -->|sets| time-resource["time-resource pipeline"]
        internal -->|sets| cron-resource["cron-resource pipeline"]
        internal -->|sets| general-task["general-task pipeline"]
        internal -->|sets| internal-etc["..."]:::ellipses
        internal -->|sets| s3-resource["s3-resource pipeline"]
    end
    
    subgraph Pages Concourse Team
        pages -->|sets| pages-dind-v25["image-dind-v25 pipeline"]
        pages -->|sets| pages-node-v20["image-node-v20 pipeline"]
        pages -->|sets| pages-python-v3["image-python-v3.11 pipeline"]
        pages -->|sets| pages-etc["..."]:::ellipses
    end

This has several advantages over individually set pipelines:

• Operators only need to manually fly one pipeline, for example container, instead of many individual pipelines, making recovery in case of system error easier.
• The single top-level pipeline can use Concourse steps like across to set each child pipeline in the exact same way, with any differences extracted as vars. This brings all the benefits of DRY to pipelines.

Design principles

• Developers should be able to adopt common pipelines with a minimum of effort. One line of code would be ideal.
• The configuration options for each pipeline should be minimal. They're the API of the pipelines; keep it simple.
• Favor convention over configuration. Repositories using common pipelines should "just work" if their folders and files are in the right place.

Development

If you want to iterate on a pipeline in this repository, consider pushing your changes to a topic branch. Topic branches do not have merge protection, so you will be able to iterate more quickly without getting pull requests approved. Change your pipeline.yml in your downstream repository to reference your topic branch instead of main in the common-pipelines resource to continuously pull in your changes. (You can consider working on a topic branch in your downstream repo as well.)

Troubleshooting

Pipeline archived after bootstrap

If your pipeline shows up as "Archived" in Concourse after running the steps in Usage, the cause could be one of the following:

• A branch is wrong. If you are using a topic branch to work on a pipeline, double-check that you updated all references from main to the topic branch. See Development. You may need to run fly destroy-pipeline to remove the archived pipeline before you can set it again.
• An input name may be wrong. Check the logs of any set_pipeline steps for errors.

Old pipeline version

After bootstrapping, Concourse will sometimes update a pipeline using outdated (possibly cached) resources. Destroy the pipeline, wait a moment, and try again.