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jobsworth

jobsworth is a small utility for creating dynamic Buildkite pipelines based on a (very slightly) higher-level description of a build and deploy process.

Buildkite's pipeline model is a flat list of steps that can either run a command, wait for previous commands to complete, or block until a user approves further process.

jobsworth defines a higher-level pipeline model with several phases:

  • Smoke Test
  • Build
  • Deploy (to potentially many environments)
  • Validate deployment (on each environment that was deployed to)

A jobsworth pipeline description looks something like this, assuming your pipeline steps are implemented via a Makefile:

smoke_test:
  - command: make test

build:
  - command: make buildkite-artifacts

deploy:
  - command: make ENV=${environment} CAUTIOUS=${cautious} buildkite-deploy
    name: ${environment}

validation_test:
  - command: make ENV=${environment} validation-test
    name: ${environment}

trivial_deploy_environments:
  - QA

cautious_deploy_environments:
  - PROD

The smoke_test, build, deploy and validation_test attributes are lists of Buildkite command steps that will be added to the pipeline after some minor adjustments.

The smoke_test and build steps are added first, and included only once.

The deploy and validation_test steps are added once for each of the environments listed under trivial_deploy_environments and cautious_deploy_environments, with the ${environment} interpolation replaced by the environment name.

trivial_deploy_environments and cautious_deploy_environments differ only in that the "trivial" environments have their deploy and validate steps run in parallel, assuming that they will be completely unattended, while the "cautious" environments will run sequentially. The deploy steps themselves may include differences based on the ${cautious} flag, which will be 1 in the cautious case and 0 otherwise.

Currently the transform is pretty rigid and designed around the workflow and preferences at Say Media. In future we may make more of this configurable, but at present that is not a goal. Further constraints are described in the following sections.

Buildkite Queues and Agent Metadata

jobsworth presumes a number of different queue names for running Buildkite agents, using different queues for each phase:

  • plan_pipeline for situations where it wants to re-run itself for some reason
  • smoke_test for the smoke test steps
  • build for the build steps
  • deploy for the deploy steps
  • validation_test for the validation test steps

We also assume that your agents have in their metadata a key environment that separates the deployment agents into a separate set per environment. There is also the concept of a "build environment" which is where the build steps themselves will run; the name of this must be provided in an environment variable called JOBSWORTH_ENVIRONMENT.

Using jobsworth in Buildkite

jobsworth is intended to be used with Buildkite's dynamic pipeline upload functionality. A Buildkite pipeline that uses jobsworth will usually have only a single command step, that runs jobsworth:

jobsworth jobsworth.yml

If successful, jobsworth will set some metadata on the build and then upload the generated pipeline.

Configuration

Jobsworth interacts with both Buildkite's Agent-specific API and its general API. When running within a Buildkite job the agent configuration proceeds automatically via environment variables, but the JOBSWORTH_BUILDKITE_API_TOKEN must be set explicitly to a general API token in order to complete configuration.

The easiest way to do this is to use the Buildkite agent's "environment" hook to set an additional environment variable containing this API token, which will then set it for all jobs run by that agent.

Generating Additional Deployment Steps

The initial jobsworth config file contains only command steps, but those steps can themselves generate further pipeline steps by uploading them with the buildkite-agent pipeline upload command.

One reason you might want to do this is to make your "cautious" deploys stop and wait for user approval before continuing:

cat <<EOT | buildkite-agent pipeline upload
steps:
  - block:
      label: "Approve Deploy"
  - command: make ENV=$JOBSWORTH_ENVIRONMENT deploy-for-real-this-time
EOT

By generating the blocking step dynamically you can skip it in cases where there's nothing new to deploy.

Interpolation Variables

Strings within the configured steps can have the following variables interpolated:

  • ${environment}: the name of the environment where the step will run. This is primarily useful on deploy steps.
  • ${branch}: the name of the git branch that the build belongs to
  • ${codebase}: a short name extracted from the git repository URL to identify the codebase. For git@github.com:example/foo.git this would be "foo".
  • ${code_version}: a version identifier for the git commit being built, in the format YYYY-MM-DD-HHMMSS-xxxxxxx-NNNNNN where xxxxxxx is an abbreviatee git commit id, the time/date fields are from that commit's creation timestamp, and NNNNNN is a zero-padded version of the Buildkite build number.
  • ${source_git_commit}: the full id of the git commit that was current when jobsworth ran.
  • ${cautious}: expands as 1 for "cautious" deploy steps, and 0 for all other steps.

Environment Variables for Steps

As a convenience to remove the need for excessive amounts of interpolation, some environment variables are also set when running commands:

  • JOBSWORTH_ENVIRONMENT is equivalent to ${environment}
  • JOBSWORTH_CODEBASE is equivalent to ${codebase}
  • JOBSWORTH_CODE_VERSION is equivalent to ${code_version}
  • JOBSWORTH_CAUTIOUS is equivalent to ${cautious}

Rolling Back a Deployment

If you need to roll back, you want to re-release an artifact that was built earlier, rather than building a new one.

jobsworth has special support for this. If you create a build via the Buildkite UI and set its message to "Roll back to #12" then the generated pipeline will omit the defined smoke_test and build steps and instead copy all of the metadata with a build: prefix from job 12 to the current build.

The deploy steps will then be generated as normal, allowing them to operate on the "stolen" metadata.

Using the message as the trigger means that it will be clear in the Buildkite summary UI when a given job is a rollback rather than a regular deployment. Other text may appear after the "magic text" so you can explain the reason for the rollback if desired: "Roll back to #12 to fix spline reticulation".

Deploying to a Custom Environment

Perhaps you have other environments that are not in the usual release path but will sometimes be deployed to for development or unusual testing reasons.

If you create a build via the Buildkite UI and set its message to "Deploy to FOO" then the generated pipeline will ignore the environments specified in the configuration and instead generate cautious deploy and validate steps for the environment FOO.

If the message is instead set to "Deploy #12 to FOO", this will combine the custom environment behavior with the rollback behavior to allow the artifacts from an earlier build to be deployed to the given named environment.