Resource Groups

In GitLab CI/CD, pipelines run concurrently by default. When you need to serialize critical jobs—such as deployments—across all pipelines in a project, resource groups provide mutual exclusion. Only one job in a given group can run at a time; the rest queue until the resource is released.

To learn more, see the CI/CD YAML syntax reference for resource_group.

Basic Workflow Example

The example below runs deploy-job on the main branch. Without a resource group, multiple pipelines could execute the deploy concurrently.

workflow:
  name: Exploring GitLab CI Concepts
  rules:
    - if: $CI_COMMIT_BRANCH == 'main'
      variables:
        DEPLOY_VARIABLE: "PRODUCTION"

deploy-job:
  stage: deploy
  script:
    - echo "Deploying application..."
    - echo "Application successfully deployed to $DEPLOY_VARIABLE environment"

Enforcing Mutual Exclusion with Resource Groups

Add the resource_group keyword to ensure that jobs sharing the same group never overlap:

deploy-to-production:
  stage: deploy
  script:
    - deploy
  resource_group: production

When several pipelines reach deploy-to-production at the same time, only one job obtains the production resource. The others wait in line.

Process Modes

Resource groups support three modes for dequeuing waiting jobs:

To update the process mode for an existing resource group, use the GitLab CI REST API.

Example: Build and Deploy Across Three Pipelines

This configuration triggers three successive pipelines. Each pipeline queues its deploy job against production:

build:
  stage: build
  script:
    - echo "Building..."

deploy:
  stage: deploy
  script:
    - echo "Deploying..."
  environment: production
  resource_group: production

• unordered: Any of deploy-1, deploy-2, or deploy-3 may run first; others wait.
• oldest_first: deploy-1 → deploy-2 → deploy-3.
• newest_first: deploy-3 → deploy-2 → deploy-1.

Demo: Simulating Long-Running Deployments

Add a sleep command to observe the queuing behavior in the GitLab UI:

name: Exploring GitLab CI Concepts
rules:
  - if: '$CI_COMMIT_BRANCH == main'
variables:
  DEPLOY_VARIABLE: "PRODUCTION"
  
deploy-job:
  stage: deploy
  resource_group: production
  script:
    - echo "Deploying application..."
    - sleep 300
    - echo "Application successfully deployed to $DEPLOY_VARIABLE environment"

1. Commit to main to trigger the first pipeline.
2. Manually schedule a second pipeline on main.

3. Cancel the first pipeline (or just its deploy-job) to free the resource.

Resource groups let you control job concurrency precisely, ensuring critical jobs never overlap across pipelines.

Links and References

• CI/CD YAML Syntax: resource_group
• GitLab CI REST API: Resource Groups
• GitLab Pipelines Documentation