pool-resource

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.

Git Repository Structure

.
├── 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.

You will need to mirror this structure in your own lock repository. In other words, initialize an empty repository and create one directory in the root of the repository for each pool of locks (e.g. aws). Inside of each lock pool directory, create one directory named claimed and one directory named unclaimed. Inside each claimed and unclaimed directory, create an empty filed named .gitkeep. Finally, create individual locks by making an empty file inside of the unclaimed directory (assuming you want your lock to be unclaimed by default) with the desired name of the lock (e.g. env-1).

Source Configuration

• 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. Ensure it does not require a password. Example:

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

• username: Optional. Username for HTTP(S) auth when pulling/pushing. This is needed when only HTTP/HTTPS protocol for git is available (which does not support private key auth) and auth is required.

• password: Optional. Password for HTTP(S) auth when pulling/pushing.

• git_config: Optional. If specified as (list of pairs name and value) it will configure git global options, setting each name with each value.

  This can be useful to set options like credential.helper or similar.

  See the git-config(1) manual page for more information and documentation of existing git options.

• 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. Valid values: 60s, 90m, 1h.

• https_tunnel: Optional. Information about an HTTPS proxy that will be used to tunnel SSH-based git commands over. Has the following sub-properties:

  • proxy_host: Required. The host name or IP of the proxy server
  • proxy_port: Required. The proxy server's listening port
  • proxy_user: Optional. If the proxy requires authentication, use this username
  • proxy_password: Optional. If the proxy requires authentication, use this password

Example

Fetching a repo with only 100 commits of history:

- get: source-code
  params: {depth: 100}

Behavior

check: Check for changes to the pool.

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

in: Fetch an acquired lock.

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.

Parameters

• depth: Optional. If a positive integer is given, shallow clone the repository using the --depth option.

out: Acquire, release, add, or remove a lock.

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

Parameters

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).

  Note: the lock must be available in your job before you can release it. In other words, a get step to fetch metadata about the lock is necessary before a put step can release the lock.

• 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.

• update: If set, we will update an existing lock in the pool.

  • If the existing lock is in the unclaimed state we will update it with the contents of the metadata file.
  • If no such lock is present in either the claimed or unclaimed state we add a new lock to the pool in the unclaimed state.
  • If the lock is in the claimed state we will wait for it to be unclaimed and proceed to update it as above.

  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.

• check: If set, we will check for an existing claimed lock in the pool and wait until it becomes unclaimed.

  • If there is an existing lock in claimed state: wait until lock is unclaimed
  • If there is an existing lock in unclaimed state: no-op
  • If no lock exists: fail

  The purpose is to simply block until a given lock in a pool is moved from a claimed state to an unclaimed state. This functionality allows us to build dependencies between disparate pipelines without the need to acquire locks.

  Note: the lock must be present to perform a check. In other words, a get step to fetch metadata about the lock is necessary before a put step can check the existence of the lock.

Example Concourse Configuration

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}

Managing multiple locks

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}

Claiming a specific lock from a pool, and releasing

The parameter for claim takes the name of a lock, and releasing the lock requires the name of the step which acquired the lock. For example:

- name: test-specific-aws
  plan:
    - put: specific-aws-env
      resource: aws-environments
      params: {claim: env-1}
    - put: aws-environments
      params: {release: specific-aws-env}

Configuring resource to proxy SSH commands through an HTTP proxy

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-----
    https_tunnel:
      proxy_host: proxy-server.mycorp.com
      proxy_port: 3128
      proxy_user: myuser
      proxy_password: myverysecurepassword

Development

Prerequisites

• golang is required - version 1.9.x is tested; earlier versions may also work.
• docker is required - version 17.06.x is tested; earlier versions may also work.
• godep is used for dependency management of the golang packages.

Running the tests

The tests have been embedded with the Dockerfile; ensuring that the testing environment is consistent across any docker enabled platform. When the docker image builds, the test are run inside the docker container, on failure they will stop the build.

Run the tests with the following command:

docker build -t pool-resource --target tests --build-arg base_image=paketobuildpacks/run-jammy-base:latest .

Note about the integration tests

If you want to run the integration tests, a bit more work is required. You will require an actual git repo to which you can push and pull, configured for SSH access. To do this, add two files to integration-tests/ssh (note that names are important):

• test_key: This is the private key used to authenticate against your repo.
• test_repo: This file contains one line of the form test_repo_url[#test_branch]. If the branch is not specified, it defaults to main. For example, git@github.com:concourse-git-tester/git-resource-integration-tests.git or git@github.com:concourse-git-tester/git-resource-integration-tests.git#testing

To set up or reset the contents of the repo, use the integration-tests/ssh/init-repo.sh script. The script clones the configured repository, (re-)creates the relevant directories, commits and pushes the changes. If you'd rather execute the commands yourself, view the script contents to understand the directory structure expected by the integration tests.

Then run the tests:

docker build -t pool-resource --build-arg base_image=concourse/golang-builder --target integrationtests .

Contributing

Please make all pull requests to the master branch and ensure tests pass locally.