Cloud Build Triggers & Config

Cloud Build triggers automate your CI/CD pipeline by starting builds in response to source code changes. When a developer pushes a commit, opens a pull request, or creates a tag, a trigger can automatically run your build pipeline — testing, building, and deploying your application without manual intervention.

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What Are Triggers?

A trigger is a Cloud Build configuration that watches a source repository for changes and starts a build when specific conditions are met. Triggers connect your source code to your build pipeline.

Trigger Components

Component	Description
Source	The repository to watch (GitHub, GitLab, Bitbucket, Cloud Source Repos)
Event	What triggers the build (push, pull request, tag)
Filter	Branch or tag patterns to match
Build config	The cloudbuild.yaml to execute (or inline steps)
Substitutions	Variables passed to the build
Service account	Identity used to run the build

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Creating Triggers

Push Trigger (Branch)

gcloud builds triggers create github \
  --name="deploy-on-push" \
  --repo-name=my-repo \
  --repo-owner=my-org \
  --branch-pattern="^main$" \
  --build-config=cloudbuild.yaml \
  --service-account=projects/my-project/serviceAccounts/cloud-build@my-project.iam.gserviceaccount.com

Pull Request Trigger

gcloud builds triggers create github \
  --name="pr-checks" \
  --repo-name=my-repo \
  --repo-owner=my-org \
  --pull-request-pattern="^main$" \
  --build-config=cloudbuild-pr.yaml \
  --comment-control=COMMENTS_ENABLED_FOR_EXTERNAL_CONTRIBUTORS_ONLY

Tag Trigger

gcloud builds triggers create github \
  --name="release-on-tag" \
  --repo-name=my-repo \
  --repo-owner=my-org \
  --tag-pattern="^v[0-9]+\.[0-9]+\.[0-9]+$" \
  --build-config=cloudbuild-release.yaml

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Substitution Variables

Substitutions allow you to parameterise builds. Cloud Build provides built-in substitutions and you can define custom ones.

Built-in Substitutions

Variable	Description
$PROJECT_ID	GCP project ID
$BUILD_ID	Unique build ID
$COMMIT_SHA	Full commit SHA
$SHORT_SHA	Short commit SHA (first 7 characters)
$BRANCH_NAME	Branch name
$TAG_NAME	Tag name (for tag triggers)
$REPO_NAME	Repository name
$REPO_FULL_NAME	Full repository name (owner/repo)
$TRIGGER_NAME	Name of the trigger

Custom Substitutions

gcloud builds triggers create github \
  --name="deploy-staging" \
  --repo-name=my-repo \
  --repo-owner=my-org \
  --branch-pattern="^main$" \
  --build-config=cloudbuild.yaml \
  --substitutions=_ENVIRONMENT=staging,_REGION=europe-west1

Use substitutions in your build config:

steps:
  - name: 'gcr.io/cloud-builders/gcloud'
    args:
      - 'run'
      - 'deploy'
      - 'my-app'
      - '--image=gcr.io/$PROJECT_ID/my-app:$SHORT_SHA'
      - '--region=$_REGION'
      - '--set-env-vars=ENVIRONMENT=$_ENVIRONMENT'

substitutions:
  _ENVIRONMENT: 'development'
  _REGION: 'europe-west1'

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Advanced Trigger Configuration

Included and Excluded Files

Only trigger builds when specific files change: