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Contributing to Concourse

It takes a lot of work from a lot of people to build a great CI system.

This document provides an outline for interacting with the Concourse community and its governance structure, as well as the nitty-gritty details how to write, test, and submit code changes.

If you run into any trouble, feel free to hang out and ask for help in the Discord!

Contribution process

The Concourse project follows an open governance model which divides project responsibilities between self-organizing teams. You can find the list of teams under the teams/ directory - each team describes its purpose and responsibilities.

The maintainers team is responsible for the issue and pull request backlog and all code within this repository, working in harmony with the core team through the RFC process to keep the Concourse product aligned with its design principles.

As a first step you can optionally add yourself as a contributor. Doing so will grant you a few things:

  1. A shiny @contributors role in Discord, allowing you to chat in #dev.
  2. The ability to triage issues and pull requests in the Concourse repo.
  3. The ability to re-trigger builds that ran for your pull requests.

If you are planning to implement a new feature, you may want to submit an RFC first - it's not necessary for every change, but requesting feedback early can help save time and effort. See "When the RFC process is necessary" for more information.

The rest of this document describes how to contribute code, but there are many other ways to contribute that are incredibly helpful: helping others or just passing time in Discussions and Discord, providing feedback on RFCs, triaging Issues, improving the documentation - any little bit helps.

Cheers! 🍻

Development process

  • Fork this repo into your GitHub account.

  • Install the development dependencies and follow the instructions below for running and developing Concourse.

  • Commit your changes and push them to a branch on your fork.

  • Here is a sample anatomy of an ideal commit:

     i       ii         iii
 |       |           |
web: structure: add var declarations

Since scripts are run in module mode, they follow the "strict mode"
semantics. Variables must be declared prior to being assigned (e.g. - iv
cannot have `x = 1` without declaring x (using var, let, or const)

concourse/concourse#5131 -------------------------------------------- v

Signed-off-by: Aidan Oldershaw <[email protected]> -------------- vi
    1. component changed
    2. structure vs behaviour
    3. brief, imperative-tense description of the change
    4. a message that tells a story
    5. mention the issue this change contributes to solving
    6. sign-off line

  • When you're ready, submit a pull request!

Pull request requirements

  • As with any community interaction, you must follow the Code of Conduct.

  • All changes must have adequate test coverage. For instruction on writing and running the various test suites, see Testing your changes.

  • All commits must have a signature certifying agreement to the DCO. For more information, see Signing your work. A check for this will run automatically and prevent merging if it fails.

  • The documentation should be updated (in a separate, linked PR), but if you're not confident in your technical writing you may skip this step.

Structure and Behaviour

In an ideal world, every pull request is small, but the codebase is large and sometimes complex changes cannot be avoided. To ease PR reviews, there are a few practices we've found helpful:

  • Focus your commits so that they only change a single component at a time.

  • Isolate structure changes from behaviour changes and label the commits appropriately - even better, batch commits of the same type into contiguous blocks.

  • Give clear prose justifications for your changes in the commit messages - it's not unusual that you do some digging to uncover the motivation for a change, but if you don't mention it in the commit message the diff can feel pretty opaque.

Development dependencies

You'll need a few things installed in order to build, test and run Concourse during development:

Concourse uses Go's module system, so make sure it's not cloned under your $GOPATH.

Running Concourse

To build and run Concourse from source, run the following in the root of this repo:

$ yarn install
$ yarn build
$ docker-compose up

Concourse will be running at localhost:8080.

Building fly and targeting your local Concourse

To build and install the fly CLI from source, run:

$ go install ./fly

This will install a fly executable to your $GOPATH/bin, so make sure that's on your $PATH!

Once fly is built, you can get a test pipeline running like this:

Log in to the locally-running Concourse instance targeted as dev:

$ fly -t dev login -c http://localhost:8080 -u test -p test

Create an example pipeline that runs a hello world job every minute: concourse/examples provides a collection of example Concourse pipelines. Use its time-triggered.yml pipeline to create a hello world job:

$ git clone [email protected]:concourse/examples.git
$ fly -t dev set-pipeline -p example -c examples/pipelines/time-triggered.yml

Unpause the example pipeline:

$ fly -t dev unpause-pipeline -p example

Developing Concourse

Concourse's source code is structured as a monorepo containing Go source code for the server components and Elm/Less source code for the web UI.

Currently, the top-level folders are confusingly cleverly named, because they were originally separate components living in their own Git repos with silly air-traffic-themed names.

directory description
/atc The "brain" of Concourse: pipeline scheduling, build tracking, resource checking, and web UI/API server. One half of concourse web.
/fly The fly CLI.
/testflight The acceptance test suite, exercising pipeline and fly features. Runs against a single Concourse deployment.
/web The Elm source code and other assets for the web UI, which gets built and then embedded into the concourse executable and served by the ATC's web server.
/go-concourse A Go client library for using the ATC API, used internally by fly.
/skymarshal Adapts Dex into an embeddable auth component for the ATC, plus the auth flag specifications for fly and concourse web.
/tsa A custom-built SSH server responsible for securely authenticating and registering workers. The other half of concourse web.
/worker The concourse worker library code for registering with the TSA, periodically reaping containers/volumes, etc.
/cmd This is mainly glue code to wire the ATC, TSA, and Garden into the single concourse CLI.
/topgun Another acceptance suite which covers operator-level features and technical aspects of the Concourse runtime. Deploys its own Concourse clusters, runs tests against them, and tears them down.

Rebuilding to test your changes

After making any changes, you can try them out by rebuilding and recreating the web and worker containers:

$ docker-compose up --build -d

This can be run in a separate terminal while the original docker-compose up command is still running.

In certain cases, when a change is done to the underlying development image (e.g. Go upgrade from 1.11 to 1.12), you will need to pull the latest version of concourse/dev image, so that web and worker containers can be built locally using the fresh image:

$ docker pull concourse/dev
$ docker-compose up --build -d

If you're working on a dependency that doesn't live under this repository (for instance, dex), you'll need to update go.mod with a replace directive with the exact reference that the module lives at:

# after pushing to the `sample` branch in your dex fork,
# try to fetch the module revision and get the version.
$ go mod download -json github.com/your-user/dex@sample | jq '.Version'
go: finding github.com/your-user/dex sample
"v0.0.0-20210401171635-fe97ad5e1a6d"

# with that version, update `go.mod` including a replace directive
$ echo 'replace github.com/concourse/dex => github.com/your-user/dex v0.0.0-20210401171635-fe97ad5e1a6d' \
  > ./go.mod

# run the usual build
$ docker-compose up --build -d

Working on the web UI

Concourse is written in Go, but the web UI is written in Elm and Less.

After making changes to web/, run the following to rebuild the web UI assets:

$ yarn install
$ yarn build

When new assets are built locally, they will automatically propagate to the web container without requiring a restart.

Debugging with dlv

With concourse already running, during local development is possible to attach dlv to either the web or worker instance, allowing you to set breakpoints and inspect the current state of either one of those.

To trace a running web instance:

$ ./hack/trace web

To trace a running worker instance:

$ ./hack/trace worker

To attach IDE debugger to a running instance, you can use the --listen flag followed by a port and the dlv will be started in headless mode listening on the specified port.

To debug a running web instance:

$ ./hack/trace web --listen 2345

To debug a running worker instance:

$ ./hack/trace worker --listen 2345

After this is done, the final step is to connect your IDE to the debugger with the following parameters:

  • host: localhost
  • port: 2345

For GoLand you can do so by going to Run | Edit Configurations… | + | Go Remote and fill in the parameters.

Trying out distributed tracing with Jaeger

Under ./hack, a docker-compose override file named jaeger.yml provides the essentials to get Jaeger running alongside the other components, as well as tying Concourse to it through the right environment variables.

To leverage that extension, run docker-compose up specifying where all the yaml files are:

$ docker-compose \
  -f ./docker-compose.yml \
  -f ./hack/overrides/jaeger.yml \
  up -d

Using the experimental containerd garden backend locally

There a docker-compose override (./hack/overrides/containerd.yml) that sets up the necessary environment variables needed to have containerd up an running as a Garden backend.

Running Vault locally

  1. Make sure you have certstrap
  2. Run ./hack/vault/setup, and follow the instructions.

See more about in the section The Vault credential manager.

Running Prometheus locally

Just like for Jaeger, we have a docker-compose override file that enhances the base docker-compose.yml with the Prometheus service, bringing with it the necessary configuraton for collecting Concourse metrics.

$ docker-compose \
  -f ./docker-compose.yml \
  -f ./hack/overrides/prometheus.yml \
  up -d

Now head to http://localhost:9090, and you'll be able to graph concourse_ Prometheus metrics.

Connecting to Postgres

If you want to poke around the database, you can connect to the db node using the following parameters:

  • host: localhost
  • port: 6543
  • username: dev
  • password: (blank)
  • database: concourse

A utility script is provided to connect via psql (or pgcli if installed):

$ ./hack/db

To reset the database, you'll need to stop everything and then blow away the db container:

$ docker-compose stop # or Ctrl+C the running session
$ docker-compose rm db
$ docker-compose start

Adding migrations

Concourse database migrations live under atc/db/migration/migrations. They are generated using Concourse's own inbuilt migration library. The migration file names are of the following format:

<migration_version>_<migration_name>.(up|down).(sql|go)

The migration version number is the timestamp of the time at which the migration files are created. This is to ensure that the migrations always run in order. There is a utility provided to generate migration files, located at atc/db/migration/cli.

To generate a migration, you have two options:

The short way

Use the create-migration script:

$ ./atc/scripts/create-migration my_migration_name
# or if you want a go migration,
$ ./atc/scripts/create-migration my_migration_name go

The long way

  1. Build the CLI:
$ cd atc/db/migration
$ go build -o mig ./cli
  1. Run the generate command. It takes the migration name, file type (SQL or Go) and optionally, the directory in which to put the migration files (by default, new migrations are placed in ./migrations):
$ ./mig generate -n my_migration_name -t sql

This should generate two files for you:

1510262030_my_migration_name.down.sql
1510262030_my_migration_name.up.sql

Now that the migration files have been created in the right format, you can fill the database up and down migrations in these files. On startup, concourse web will look for any new migrations in atc/db/migration/migrations and will run them in order.

Testing your changes

Any new feature or bug fix should have tests written for it. If there are no tests, it is unlikely that your pull request will be merged, especially if it's for a substantial feature.

There are a few different test suites in Concourse:

  • unit tests: Unit tests live throughout the codebase (foo_test.go alongside foo.go), and should probably be written for any contribution.

  • testflight/: This suite is the "core Concourse" acceptance tests suite, exercising pipeline logic and fly execute. A new test should be added to testflight for most features that are exposed via pipelines or fly.

  • web/elm/tests/: These test the various Elm functions in the web UI code in isolation. For the most part, the tests for web/elm/src/<module name>.elm will be in web/elm/tests/<module name>Tests.elm. We have been finding it helpful to test the update and view functions pretty exhaustively, leaving the models free to be refactored.

  • web/wats/: This suite covers specifically the web UI, and run against a real Concourse cluster just like testflight. This suite is still in its early stages and we're working out a unit testing strategy as well, so expectations are low for PRs, though we may provide guidance and only require coverage on a case-by-case basis.

  • topgun/: This suite is more heavyweight and exercises behavior that may be more visible to operators than end-users. We typically do not expect pull requests to add to this suite.

If you need help figuring out the testing strategy for your change, ask in Discord!

Concourse uses Ginkgo as its test framework and suite runner of choice for Go code. You'll need to install the ginkgo CLI to run the unit tests and testflight:

$ go get github.com/onsi/ginkgo/ginkgo

We use Counterfeiter to generate fakes for our unit tests. You may need to regenerate fakes if you add or modify an interface. You can generate the fakes by running

$ go generate ./...

in the directory where the interface is located.

Running unit tests

Concourse is a ton of code, so it's faster to just run the tests for the component you're changing.

To run the tests for the package you're in, run:

$ ginkgo -r -p

This will run the tests for all packages found in the current working directory, recursively (-r), running all examples within each package in parallel (-p).

You can also pass the path to a package to run as an argument, rather than cding.

Note that running go test ./... will break, as the tests currently assume only one package is running at a time (the ginkgo default). The go test default is to run each package in parallel, so tests that allocate ports for test servers and such will collide with each other.

Running elm tests

You can run yarn test from the root of the repo or elm-test from the web/elm directory. They are pretty snappy so you can comfortably run the whole suite on every change.

Elm static analysis

Running yarn analyse will run many checks across the codebase and report unused imports and variables, potential optimizations, etc. Powered by elm-analyse. If you add the -s flag it will run a server at localhost:3000 which allows for easier browsing, and even some automated fixes!

Elm formatting

Run yarn format to format the elm code according to the official Elm Style Guide. Powered by elm-format.

Elm benchmarking

Run yarn benchmark.

Running the acceptance tests (testflight)

The testflight package contains tests that run against a real live Concourse. By default, it will run against localhost:8080, i.e. the docker-compose up'd Concourse.

If you've already got Concourse running via docker-compose up, you should be able to just run the acceptance tests by running ginkgo the same way you would run it for unit tests:

$ ginkgo -r -p testflight

Note: because testflight actually runs real workloads, you may want to limit the parallelism if you're on a machine with more than, say, 8 cores. This can be done by specifying --nodes:

$ ginkgo -r --nodes=4 testflight

Running the web acceptance tests (web/wats)

Run yarn test from the web/wats directory. They use puppeteer to run a headless Chromium. A handy fact is that in most cases if a test fails, a screenshot taken at the moment of the failure will be at web/wats/failure.png. There is a known issue with running these tests in parallel (which is the default setting). The issue stems from an upstream dependency, so until it is fixed you can run yarn test --serial to avoid it.

Running Kubernetes tests

Kubernetes-related testing are all end-to-end, living under topgun/k8s. They require access to a real Kubernetes cluster with access granted through a properly configured ~/.kube/config file.

kind is a great choice when it comes to running a local Kubernetes cluster - all you need is docker, and the kind CLI. If you wish to run the tests with a high degree of concurrency, it's advised to have multiple kubernetes nodes. This can be achieved with the following kind config:

kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
- role: worker
- role: worker
- role: worker
- role: worker

With the cluster up, the next step is to have a proper Tiller setup (the tests still run with Helm 2):

kubectl create serviceaccount \
	--namespace kube-system \
	tiller

kubectl create clusterrolebinding \
	tiller-cluster-rule \
	--clusterrole=cluster-admin \
	--serviceaccount=kube-system:tiller

helm init \
	--service-account tiller \
	--upgrade

The tests require a few environment variables to be set:

  • CONCOURSE_IMAGE_TAG or CONCOURSE_IMAGE_DIGEST: the tag or digest to use when deploying Concourse in the k8s cluster
  • CONCOURSE_IMAGE_NAME: the name of the image to use when deploying Concourse to the Kubernetes cluster
  • HELM_CHARTS_DIR: path to a clone of the helm/charts repo. This is used to define the postgres chart that Concourse depends on.
  • CONCOURSE_CHART_DIR: location in the filesystem where a copy of the Concourse Helm chart exists.

With those set, go to topgun/k8s and run Ginkgo:

# run the test cases serially
ginkgo .

# run the test cases with a concurrency level of 16
ginkgo -nodes=16 .

A note on topgun

The topgun/ suite is quite heavyweight and we don't currently expect most contributors to run or modify it. It's also kind of hard for mere mortals external contributors to run anyway.

To run topgun, a BOSH director up and running is required - the only requirement with regards to where BOSH sits is having the ability to reach the instance that it creates (the tests make requests to them).

You can have a local setup by leveraging the dev scripts in the concourse-bosh-release repo:

# clone the concourse-bosh-release repository
#
git clone https://github.com/concourse/concourse-bosh-release cbr && cd $_


# run the setup script
#
./dev/vbox/setup

setup will take care of creating the BOSH director (aliased as vbox), uploading basic releases that we need for testing, as well as a BOSH Lite stemcell.

With the director up, we can head to the tests.

# fetch the concourse repo, and get into it
#
git clone https://github.com/concourse/concourse concourse && cd $_

# get inside the topgun suite that you want to work on.
#
cd ./topgun/$SUITE

# run the tests of that suite
#
BOSH_ENVIRONMENT=vbox ginkgo -v .

ps.: you must have already installed the BOSH cli first.

Signing your work

Concourse has joined other open-source projects in adopting the Developer Certificate of Origin process for contributions. The purpose of the DCO is simply to determine that the content you are contributing is appropriate for submitting under the terms of our open-source license (Apache v2).

The content of the DCO is as follows:

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
San Francisco, CA, 94129

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

This is also available at https://developercertificate.org.

All commits require a Signed-off-by: signature indicating that the author has agreed to the DCO. This must be done using your real name, and must be done on each commit. This line can be automatically appended via git commit -s.

Your commit should look something like this in git log:

commit 8a0a135f8d3362691235d057896e6fc2a1ca421b (HEAD -> master)
Author: Alex Suraci <[email protected]>
Date:   Tue Dec 18 12:06:07 2018 -0500

    document DCO process

    Signed-off-by: Alex Suraci <[email protected]>

If you forgot to add the signature, you can run git commit --amend -s. Note that you will have to force-push (push -f) after amending if you've already pushed commits without the signature.