Welcome to the tutorial on parallel and sequential execution in CircleCI! CircleCI allows you to execute jobs in parallel or sequential order to optimize your CI/CD pipeline. In this tutorial, we will guide you through the process of configuring parallel and sequential execution in CircleCI. Let's get started!
Step 1: Defining Jobs and Dependencies
To control the execution order of jobs, you need to define them in your CircleCI configuration file (.circleci/config.yml) and specify their dependencies. Jobs without dependencies will run in parallel, while jobs with dependencies will run sequentially.
Here's an example of a CircleCI configuration file with jobs defined in parallel:
version: 2
jobs:
test-frontend:
docker:
- image: circleci/node:14.17
steps:
- checkout
- run: npm install
- run: npm test
test-backend:
docker:
- image: circleci/node:14.17
steps:
- checkout
- run: npm install
- run: npm test
In this example, the "test-frontend" and "test-backend" jobs are defined without any dependencies. Therefore, they will run in parallel, allowing for faster execution of the pipeline.
Step 2: Specifying Dependencies
If you want to run jobs sequentially, you can specify their dependencies using the requires keyword. Jobs listed under the requires section will be executed in the order specified.
Here's an example of a CircleCI configuration file with jobs defined in a sequential order:
version: 2
jobs:
build:
docker:
- image: circleci/node:14.17
steps:
- checkout
- run: npm install
- run: npm build
test:
docker:
- image: circleci/node:14.17
steps:
- checkout
- run: npm install
- run: npm test
deploy:
requires:
- build
- test
docker:
- image: circleci/node:14.17
steps:
- checkout
- run: npm install
- run: npm run deploy
In this example, the "deploy" job is specified to require the "build" and "test" jobs. This ensures that the deployment only happens when both the build and test phases are successfully completed.
Common Mistakes when Working with Parallel and Sequential Execution:
- Not properly defining dependencies between jobs, leading to incorrect execution order.
- Overusing parallel execution, which can result in resource contention and slower overall performance.
- Forgetting to consider the impact of dependencies when optimizing build times.
Frequently Asked Questions about Parallel and Sequential Execution in CircleCI:
-
Q: Can I mix parallel and sequential execution in the same workflow?
A: Yes, you can have a combination of parallel and sequential execution in your CircleCI workflow. It allows you to optimize the execution order based on your project's requirements.
-
Q: How many jobs can I run in parallel?
A: The number of jobs that can run in parallel depends on your CircleCI plan. CircleCI provides different concurrency limits based on the plan you choose.
Summary
In this tutorial, we discussed how to configure parallel and sequential execution in CircleCI to optimize your CI/CD pipeline. We covered the steps of defining jobs and dependencies, specifying dependencies for sequential execution, and common mistakes to avoid. We also provided answers to frequently asked questions. By effectively utilizing parallel and sequential execution in CircleCI, you can streamline your build process and improve overall efficiency.