UPDATE

This tool and repo is no longer used nor maintained by pivotaltracker. If anyone wishes to take over ownership and maintenance, please open an issue.

Concourse Branch Manager

Automatically build arbitrary branches on Concourse CI without relying on Github pull requests.

See and vote for this issue to get official support for building arbitrary branches without pull requests added to Concourse.

Overview

This is a Concourse build task to find all existing branch names which match selected (1) criteria.

Then, a branch-manager pipeline will be dynamically created/updated, using the concourse Fly CLI to create it "on the fly" (no pun intended), which will contain for a job + build plan for each branch, based on YAML ERB templates (2).

It is intended to be used with the Concourse git-branches-resource (3) which is published on Docker Hub at tracker/git-branches-resource to determine when and which branches should be built. However, any resource that fulfills the same input contract at the git-branches-resource can be used. NOTE: That there is now an identically named git-branches-resource which is published on Docker Hub at cfcommunity/git-branches-resource, however, this one is does NOT currently have some of the features which tracker/git-branches-resource has, such as regex matching and a max branches limit. The rest of this documentation assumes you are using the latter. Caveat Emptor.

(1) The "selected" branches can be based a regex config option passed to the git-branches-resource (3) or other resource which fulfills the resource 'input' contract to write out a git-branches.json containing a hash with a uri to the repo, and an array of branches. This list of branches can be controlled with a regex (e.g. all branches starting with a string like feature-, release-candidate-, etc), and also limit the maximum number of branches listed. See the Concourse git-branches-resource documentation for more details. NOTE: In the future, support will be added for automatically building branches for GitHub pull requests, via this same git-branches.json input resource interface.
(2) the specified resource and job YAML ERB templates can contain whatever job/plan processing is needed, and the name of the dynamically-selected git branch will be passed as a param, to be interpolated into the YAML via ERB.

How it works

In your Concourse pipeline, you will add a git resource and a job which will run Concourse Branch Manager, and specify the necessary parameters, including credentials to manage your Concourse instance.
When the job runs its tasks, it will dynamically create/update a new pipeline which will contain resources and jobs for all your dynamically processed branches.
The resources and jobs/plans/tasks which are automatically created in the pipeline are configurable to do whatever is needed for your particular situation and build/deployment environment.

Setup and Usage

0. Enable Concourse authentication

The branch manager will not work with non-authenticating (development mode) Concourse instances. Any password based authentication mecanism will do (Basic, OAuth...)

1. Edit and update your Concourse pipeline to add the three required concourse-branch-manager resources

Add the following resources to your Concourse pipeline YAML file:

- name: concourse-branch-manager
  type: git
  source:
    uri: https://github.com/pivotaltracker/concourse-branch-manager.git
    branch: master
    ignore_paths: [Gemfile, Gemfile.lock]

# This `git-branches` input resource determines which branches will be processed
- name: branch-manager-git-branches
  type: git-branches
  source:
    # Set this to the uri of your repo for which you want to dynamically build arbitrary branches
    uri: https://github.com/mygithubuser/my-repo
    branch_regexp: ".*"
    max_branches: 20

# This repo containing your resource/job templates can be the same repo as
# the one in the git-branches resource above, but it doesn't have to be
- name: branch-manager-templates
  type: git
  source:
    uri: https://github.com/mygithubuser/my-template-repo
    branch: master
    paths: [ci/templates/*]

# This repo contains any non-secret non-credential config that needs to be
# passed into your generated pipeline via fly --load-vars-from options
- name: branch-manager-config
  type: git
  source:
    # Set this to the uri of your repo containing your non-secret non-credential config
    uri: https://github.com/pivotaltracker/concourse-branch-manager.git
    branch: master
#    paths: [ci/config/*]

# This repo contains any secret credential config that needs to be
# passed into your generated pipeline via fly --load-vars-from options
- name: branch-manager-credentials
  type: git
  source:
    # Set this to the uri of your repo containing your non-secret non-credential config
    uri: https://github.com/pivotaltracker/concourse-branch-manager.git
    branch: master
#    paths: [ci/credentials/*]

The concourse-branch-manager resource will always point to the concourse-branch-manager public repo on github, and should look exactly as the above example. This is where the logic for the branch-building task lives.
Set the uri of the branch-manager-git-branches resource with the uri of your repo for which you want to dynamically build arbitrary branches.
Set the uri of the branch-manager-templates resource with the uri of your your git resource containing your resource/job templates for building branches. NOTE: This may both point to the same git repo as your git-branches resource, but it doesn't have to.

2. Edit and update your Concourse pipeline to add the branch-manager job:

Add the following job to your Concourse pipeline YAML file:

- name: branch-manager
  serial: true
  plan:
  - get: concourse-branch-manager
    params: {depth: 20}
    trigger: true
  - get: git-branches
    resource: branch-manager-git-branches
    trigger: true
  - get: template-repo
    resource: branch-manager-templates
    params: {depth: 20}
    trigger: true
  - get: config-repo
    resource: branch-manager-config
    params: {depth: 20}
    trigger: true
  - get: credentials-repo
    resource: branch-manager-credentials
    params: {depth: 20}
    trigger: true    
  - task: manage-branches
    file: concourse-branch-manager/tasks/manage-branches.yml
    config:
      params:
        BRANCH_RESOURCE_TEMPLATE: template-repo/ci/templates/my-repo-branch-resource-template.yml.erb
        BRANCH_JOB_TEMPLATE: template-repo/ci/templates/my-repo-branch-job-template.yml.erb
        CONCOURSE_URL: {{CONCOURSE_URL}}
        CONCOURSE_USERNAME: {{CONCOURSE_USERNAME}}
        CONCOURSE_PASSWORD: {{CONCOURSE_PASSWORD}}
        CONCOURSE_TEAM: {{CONCOURSE_TEAM}} # Add this if you have a team

You may specify the CONCOURSE_* params directly in your pipeline YAML file, but since they are sensitive credentials, you should handle them via Concourse's support for template variables.

If you're using the teams feature and want to add the pipeline to a team other than main, specify it in the CONCOURSE_TEAM params. If this params is omitted, no team will be specified.

There are several params available to configure the templates. Each is a path to a file containing an ERB template.

BRANCH_RESOURCE_TEMPLATE - resources to be added to each branch
BRANCH_JOB_TEMPLATE - jobs to be added to each branch
PIPELINE_COMMON_RESOURCES_TEMPLATE - resources which will be added only once to the pipeline
PIPELINE_RESOURCE_TYPE_TEMPLATE - resource types to be added to the pipeline

These templates can live in your managed repo, but they don't have to - you could add an additional resource to the branch-manager job to contain them. More details on this below...

TODO: Document PIPELINE_LOAD_VARS_FROM_N params TODO: Document PIPELINE_NAME param TODO: Document GROUP_PER_BRANCH param

3. Edit and update your Concourse pipeline to add the branch-manager group (optional):

- name: branch-manager
  jobs:
  - branch-manager

4. Add the git-branch resource type to your pipeline (optional)

resource_types:
- name: git-branches
  type: docker-image
  source:
    repository: tracker/git-branches-resource

5. Create a YAML ERB templates for your resource and job which will be run for each branch

Each arbitrary branch which is dynamically detected will have a Concourse resource automatically created for it, and a Concourse job, build plan, and task will also be automatically created to process it.

You have control over what this resource and job do by providing ERB templates which will be used to build separate resource and job entries in the generated pipeline for each branch which is processed.

The path to your ERB templates is specified in the BRANCH_RESOURCE_TEMPLATE and BRANCH_JOB_TEMPLATE parameters, as documented above. They are paths to ERB templates which will be used to dynamically generate a resource and job for each of your branches. These templates can live in your managed repo, but they don't have to - you could add an additional resource to the branch-manager job to contain them.

The only requirement for these ERB templates is that they use ERB to interpolate the uri and branch_name variables, which are automatically set to contain the repo uri and name of the branch which was automatically detected and processed, and for which builds should be triggered.

And, of course, you must create and properly reference a task configuration and associated script, as well as any additional resources you need, to do the actual work of your job. This can be whatever you want - using a Concourse git or s3 resource output to push a branch or s3 artifact, which can then be used by other hardcoded jobs in your pipeline. Here is an example task configuration and script from the concourse-branch-manager project itself.

Here is an example branch resource template (this is an actual example from the concourse-branch-manager project itself):

name: my-repo-branch-<%= branch_name %>
type: git
source:
  uri: <%= uri %>
  branch: <%= branch_name %>

And here is an example branch job template (this is an actual example from the concourse-branch-manager project itself):

name: my-repo-branch-job-<%= branch_name %>
plan:
- get: my-repo-branch
  resource: my-repo-branch-<%= branch_name %>
  params: {depth: 20}
  trigger: true
- task: my-repo-branch-task
  file: my-repo-branch/ci/tasks/my-repo-branch-task.yml
  config:
    params:
      BRANCH_NAME: <%= branch_name %>

6. Create/Update the Concourse pipeline

Update your Concourse pipeline with the new resources and job using the fly set-pipeline command.

Alternate configuration options

The implementation above is flexible. Based on your situation, you can any combination of one or more pipelines, git-branches resources, template git resources, branch-manager jobs, resource templates, and job templates.

For example, you can have one pipeline per branch, one pipeline with multiple branches, multiple pipelines with multiple branches, multiple jobs with different templates using different resources - whatever works for you.

The resource naming is also flexible to allow you to have multiple git-branches or template git resources in the same pipeline YAML file. The only requirement is that the get entries in your task must be named concourse-branch-manager, git-branches, and template-repo, since these are referred to by the task branch-building logic.

Live Example

There is a working example pipeline which points to example templates and a dummy task in the concourse-branch-manager project repo)

To try it out yourself:

(at the beginning of the day) Login to fly and save credentials in a ci target:
```
fly login --target=ci --concourse-url=https://my-concourse-server
```
Clone a local copy of the branch-manager-example repo. Note that this has all the Concourse config in an examples directory, but in your actual projects you may want to want to put this in a ci directory by convention.
Create a secrets.yml file containing the vars specifying the uri and credentials of your Concourse server. Put this some where secret and don't check it in! For convenience, secrets.yml in the root of this repo is gitignored, so you can put it there if you want:
```
# secrets.yml
CONCOURSE_URL: https://my-concourse-server.example.com
CONCOURSE_USERNAME: my-basic-auth-concourse-username
CONCOURSE_PASSWORD: my-basic-auth-concourse-password
```

Use the fly set-pipeline command to create/update the branch-manager-example pipeline:

fly --target=ci set-pipeline --config=examples/pipelines/branch-manager-example.yml --load-vars-from=secrets.yml --pipeline=branch-manager-example

(first time only) Use the fly unpause-pipeline commmand to unpause the pipeline the first time it is created (or just click unpause in the Concourse UI):
```
fly --target=ci unpause-pipeline --pipeline=branch-manager-example
```
Go to your Concourse UI (e.g. https://my-concourse-server.example.com), and select the branch-manager-example pipeline from the upper-left hamburger menu.
It should successfully build automatically in a few seconds and go green
Refresh the page, and select the autocreated branch-manager pipeline from the upper-left hamburger menu. It should contain some of the dummy branches on the concourse-branch-manager repo. They should also all successfully build after a few seconds.

That's it! Use this as a template and example for using concourse-branch-manager in your own project!

Dealing with Concourse UI issues due to many branches/groups

It is recommended that you keep the number of branches limited. The git-branches-resource resource by default limits you to 20, but the Concourse UI starts having layout issues with fewer than that. The biggest problem is z-index issues that prevent usage of the pipelines menu.
This issue against Concourse ATC (the Concourse UI) reports these issues, and contains a javascript bookmarklet that makes some hacks to fix the issues. The recommended fix by the concourse team would be to make the groups scrollable like the build numbers at the top of a build page. A pull request would be welcome ;)

sam-myers / concourse-branch-manager