I worked on setting up a continuous delivery pipeline for our team, so when code is merged to a test branch, it’s automatically deployed to a test environment. I wanted to reuse the deployment pipelines already written because they do a good job handling the nuances between each microservice we deploy.

My solution at a high level was a lot like this:

  1. Code is deployed to a test-branch branch.
  2. A Bitbucket pipeline is kicked off that triggers the deploy.
  3. The deploy script deploys a microservice to an environment, test.

This seemed really straightforward on the surface, except its a little harder than I initially thought.

Let’s imagine our Bitbucket pipelines look like this:

# deploys service-a
deploy-service-a: &deploy-service-a
  step:
    image: node:12
    name: service-a
    script:
      cd service-a
      serverless deploy --stage ${STAGE}

# sets the STAGE variable that's defined when the pipeline is manually triggered
set-variables: &set-variables
  variables:
    - name: STAGE
      default: "${STAGE}"

pipelines:
  # our custom pipeline, what shows up Bitbucket web app
  custom:
    deploy:
      - <<: *set-variables
      - <<: *deploy-service-a

How this works:

  1. A developer manually triggers the deploy pipeline, specifying the STAGE variable in the Bitbucket web app
  2. STAGE is set and assigned to the STAGE variable via set-variables
  3. deploy-service-a is kicked off, executes, and deploys new code for service-a in the appropriate stage.

Struggle

This works well for manual deployments. However, I needed to have this triggered automatically. So I update the pipelines object and added:

pipelines:

  branches:
    test-branch:
      - <<: *deploy

Theoretically, this triggers deploy to execute whenever there is a commit to test-branch, however this fails spectacularly because the STAGE variable is not defined.

I try the following:

pipelines:

  branches:
    variables:
      - name: STAGE
        default: test
    test-branch:
      - <<: *deploy

I soon find out that you can only add a variables object to custom pipelines. Honestly, this is where I start to lose my mind, having spent hours on something that should be simple and straightforward.

Animated GIF of me losing my mind

Solution

Fortunately, for me, I’m able to string together a correct seqeuence of characters and words and executed the perfect Google search and found a solution on StackOverflow.

First, there were a few limitations of Bitbucket I hadn’t realized until I went on this journey:

  1. Only custom pipelines can have a variables object.
  2. You cannot pass variables between steps (because each step is it’s own deploy, with it’s own scope, docker image, variables, etc.).

However, I learned I can get around this by using artifacts. We’d normally use artifacts to save packaged binaries or test results that were executed during a Bitbucket pipeline run. They can be used to pass data between steps as well.

Armed with my newly found knowledge, by Bitbucket pipelines were refactored into:

deploy-service-a: &deploy-service-a
  step:
    image: node:12
    name: service-a
    script:
      - if [ -e set_env.sh ]; then
      -   cat set_env.sh
      -   source set_env.sh
      - fi
      cd service-a
      serverless deploy --stage ${STAGE}

set-variables: &set-variables
  variables:
    - name: STAGE
      default: "${STAGE}"

pipelines:
  custom:
    deploy:
      - <<: *set-variables
      - <<: *deploy-service-a
  
  branches:
    test-branch:
      - step:
        name: Save stage
        script: 
          - STAGE="test"
          - echo $STAGE
          - echo "export STAGE=$STAGE" >> set_env.sh
        artifacts:
          - set_env.sh
      - <<: *deploy

This works perfectly. If you look closely to the output when running this Bitbucket pipeline, you’ll see something in deploy-service-a's Build setup phase that resembles:

Artifact "set_env.sh": Downloading
Artifact "set_env.sh": Downloaded 140 B in 0 seconds
Artifact "set_env.sh": Extracting
Artifact "set_env.sh": Extracted in 0 seconds

Artifacts from previous steps are passed to subsequent steps!

Thanks for reading. ✊🏿