a pool of locks (modeling semaphores)

Allows you to lock environments, pipeline flow, or other entities which have to be interacted with in a serial manner.

This resource is backed by a Git repository, so the configuration is largely the same as the git-resource.

.
├── aws
│   ├── claimed
│   │   ├── .gitkeep
│   │   └── env-2
│   └── unclaimed
│       ├── .gitkeep
│       └── env-1
├── ping-pong-tables
│   ├── claimed
│   │   └── .gitkeep
│   └── unclaimed
│       ├── .gitkeep
│       └── north-table
└── vsphere
    ├── claimed
    │   ├── .gitkeep
    │   └── f3cb3823-a45a-49e8-ab41-e43268494205
    └── unclaimed
        ├── .gitkeep
        └── 83ed9977-3a10-4c49-a818-2d7a37693da7

This structure represents 3 pools of locks, aws, ping-pong-tables, and vsphere. The .gitkeep files are required to keep the unclaimed and claimed directories track-able by Git if there are no files in them.

• uri: Required. The location of the repository.

• branch: Required. The branch to track.

• pool: Required. The logical name of your pool of things to lock.

• private_key: Optional. Private key to use when pulling/pushing. Example:

  private_key: |
    -----BEGIN RSA PRIVATE KEY-----
    MIIEowIBAAKCAQEAtCS10/f7W7lkQaSgD/mVeaSOvSF9ql4hf/zfMwfVGgHWjj+W
    <Lots more text>
    DWiJL+OFeg9kawcUL6hQ8JeXPhlImG6RTUffma9+iGQyyBMCGd1l
    -----END RSA PRIVATE KEY-----
  

• retry_delay: Optional. If specified, dictates how long to wait until retrying to acquire a lock or release a lock. The default is 10 seconds.

The repository is cloned (or pulled if already present), and any commits made after the given version for the specified pool are returned. If no version is given, the ref for HEAD is returned.

Outputs 2 files:

• metadata: Contains the contents of whatever was in your lock file. This is useful for environment configuration settings.

• name: Contains the name of lock that was acquired.

Performs one of the following actions to change the state of the pool.

One of the following is required.

• acquire: If true, we will attempt to move a randomly chosen lock from the pool's unclaimed directory to the claimed directory. Acquiring will retry until a lock becomes available.

• claim: If set, the specified lock from the pool will be acquired, rather than a random one (as in acquire). Like acquire, claiming will retry until the specific lock becomes available.

• release: If set, we will release the lock by moving it from claimed to unclaimed. The value is the path of the lock to release (a directory containing name and metadata), which typically is just the step that provided the lock (either a get to pass one along or a put to acquire).

• add: If set, we will add a new lock to the pool in the unclaimed state. The value is the path to a directory containing the files name and metadata which should contain the name of your new lock and the contents you would like in the lock, respectively.

• add_claimed: Exactly the same as the add param, but adds a lock to the pool in the claimed state.

• remove: If set, we will remove the given lock from the pool. The value is the same as release. This can be used for e.g. tearing down an environment, or moving a lock between pools by using add with a different pool in a second step.

The following example pipeline models acquiring, passing through, and releasing a lock based on the example git repository structure:

resources:
- name: aws-environments
  type: pool
  source:
    uri: git@github.com:concourse/locks.git
    branch: master
    pool: aws
    private_key: |
      -----BEGIN RSA PRIVATE KEY-----
      MIIEowIBAAKCAQEAtCS10/f7W7lkQaSgD/mVeaSOvSF9ql4hf/zfMwfVGgHWjj+W
      <Lots more text>
      DWiJL+OFeg9kawcUL6hQ8JeXPhlImG6RTUffma9+iGQyyBMCGd1l
      -----END RSA PRIVATE KEY-----

jobs:
- name: deploy-aws
  plan:
    - put: aws-environments
      params: {acquire: true}
    - task: deploy-aws
      file: my-scripts/deploy-aws.yml

- name: test-aws
  plan:
    - get: aws-environments
      passed: [deploy-aws]
    - task: test-aws
      file: my-scripts/test-aws.yml
    - put: aws-environments
      params: {release: aws-environments}

The parameter for release is the name of the step whose lock to release. Normally this is just the same as the name of the resource, but if you have custom names for put (for example if you need to acquire multiple instances of the same pool), you would put that name instead. For example:

- name: test-multi-aws
  plan:
    - put: environment-1
      resource: aws-environments
      params: {acquire: true}
    - put: environment-2
      resource: aws-environments
      params: {acquire: true}
    - task: test-multi-aws
      file: my-scripts/test-multi-aws.yml
    - put: aws-environments
      params: {release: environment-1}
    - put: aws-environments
      params: {release: environment-2}