Thanks to my colleague John Pignata for a great blog on how to create a continuous deployment pipeline to Amazon ECS.
Delivering new iterations of software at a high velocity is a competitive advantage in today’s business environment. The speed at which organizations can deliver innovations to customers and adapt to changing markets is increasingly a pivotal attribute that can make the difference between success and failure.
AWS provides a set of flexible services designed to enable organizations to embrace the combination of cultural philosophies, practices, and tools called DevOps that increases an organization’s ability to deliver applications and services at high velocity.
In this post, I explore the DevOps practice called continuous deployment and outline a reference architecture to implement an automated deployment pipeline for applications delivered as Docker containers onto Amazon ECS using AWS CodePipeline, AWS CodeBuild, and AWS CloudFormation.
What is continuous deployment?
Agility is often cited as a key advantage of cloud computing over the traditional delivery of IT resources. Instead of waiting weeks or months for other departments to provision a new server, developers can create new instances with a click or API call and start using it within minutes. This newfound speed and autonomy frees developers to experiment and deliver new products and features to their customers as quickly as possible.
On top of the cloud, teams are embracing DevOps practices in order to achieve a faster time-to-market, better code quality, and more reliable releases of their products and services. Continuous deployment is a DevOps practice in which new software revisions are automatically built, tested, packaged, and released to production.
Continuous deployment enables developers to ship features and fixes through an entirely automated software release process. Instead of batching up large releases over a period of weeks or months and conducting deployments manually, developers can use automation to deliver versions of their applications many times a day as new software revisions are ready for users. In the same way cloud computing abbreviates the delivery time of resources, continuous deployment reduces the release cycle of new software to your users from weeks or months to minutes.
Embracing this speed and agility has many benefits including:
- New features and bug fixes are released to users quickly; code sitting in a source code repository does not deliver business value or benefit your customers. By releasing new software revisions as close to immediately as possible, customers start benefiting from your work more quickly and teams can get more focused feedback.
- Change sets are smaller; large change sets create challenges in pinpointing root causes of issues, bugs, and other regressions. By releasing smaller change sets more frequently, teams can more easily attribute and correct introduced issues.
- Automated deployment encourages best practices; as any change committed to your source code repository can be deployed immediately via automation, teams have to ensure that changes are well-tested and that their production environments are closely monitored.
How does continuous deployment work?
Continuous deployment is conducted by an automated pipeline that coordinates the activities related to software release and provides visibility into the process. During the process, a releasable artifact is built, tested, packaged, and deployed into a production environment. The releasable artifact might be an executable file, a package of script files, a container, or some other component that ultimately must be delivered to production.
AWS CodePipeline is a continuous delivery and deployment service that coordinates the building, testing, and deployment of your code each time there is a new software revision. CodePipeline provides visible, central orchestration for taking a code change and moving it through a workflow and ultimately into the hands of your users. The pipeline defines stages to retrieve code from a source code repository, build the source code into a releasable artifact, test that artifact, and deliver it to production while ensuring that these stages happen in order and are halted if a failure occurs.
While CodePipeline powers the delivery pipeline and orchestrates the process, it does not have facilities for building or testing the software itself. For these stages, CodePipeline integrates with several other tools, including AWS CodeBuild, which is a fully managed build service. CodeBuild compiles source code, runs tests, and produces software packages that are ready to deploy. That makes it ideal for the build and test stages of a continuous deployment pipeline. Out of the box, CodeBuild has native support for many different kinds of build environments, including building Docker containers.
Containers are a powerful mechanism for software delivery, as they allow for a predictable and reproducible environment and provide a high level of confidence that changes tested in one environment can be successfully deployed. AWS provides several services to run and manage Docker container images. Amazon ECS is a highly scalable and high performance container management service that allows you to run applications on a cluster of Amazon EC2 instances. Amazon ECR is a fully managed Docker container registry that makes it easy for developers to store, manage, and deploy Docker container images.
Finally, CodePipeline integrates with several services to facilitate deployment, including AWS Elastic Beanstalk, AWS CodeDeploy, AWS OpsWorks, and your own custom deployment code or process using AWS Lambda or AWS CloudFormation. These deployment actions can be used to power the final step in your pipeline to push the newly built changes live onto your production environment.
Continuous deployment to Amazon ECS
Here’s a reference architecture that puts these components together to deliver a continuous deployment pipeline of Docker applications onto ECS:
This architecture demonstrates how to deploy containers onto ECS and ECR using CodePipeline to build a fully automated continuous deployment pipeline on top of AWS. This approach to continuous deployment is entirely serverless and uses managed services for the orchestration, build, and deployment of your software.
The pipeline created in the reference architecture looks like the following:
In this post, I discuss each stage in this reference architecture. What happens when a developer changes some copy on a landing page and pushes that change into the source code repository?
First, in the Source stage, the pipeline is configured with details for accessing a source code repository system. In the reference architecture, you have a sample application hosted in a GitHub repository. CodePipeline polls this repository and initiates a new pipeline execution for each new commit. In addition to GitHub, CodePipeline also supports source locations such as a Git repository in AWS CodeCommit or a versioned object stored in Amazon S3. Each new build is retrieved from the source code repository, packaged as a zip file, stored on S3, and sent to the next stage of the pipeline.
The Source stage also defines a template artifact stored on Amazon S3. This is the template that defines the deployment environment used by the deployment stage after a successful build of the application.
The Build stage uses CodeBuild to create a new Docker container image based upon the latest source code and pushes it to an ECR repository. CodePipeline also integrates with a number of third-party build systems, such as Jenkins, CloudBees, Solano CI, and TeamCity.
Finally, the Deploy stage uses CloudFormation to create a new task definition revision that points to the newly built Docker container image and updates the ECS service to use the new task definition revision. After this is done, ECS initiates a deployment by fetching the new Docker container from ECR and restarting the service.
After all of the pipeline’s stages are green, you can reload the application in a web browser and see the developer’s copy changes live in production. This happened automatically without any human invention.
This pipeline is now in production, listening for new code in the source code repository, and ready to ship any future changes that your team pushes into production. It’s also extensible, meaning that new stages can be added to include additional steps. For example, you could include a test stage to execute unit and acceptance tests to ensure the new code revision is safe to deploy to production. After it’s deployed, a notification step could be added to alert your team via email or a Slack channel that a new version is live, along with the details about the change set deployed to production.
We’re excited to see what kinds of applications you can deliver to your users using this approach and how it affects your product development processes. The cloud unlocks massive advantages in agility, and the ability to implement techniques like continuous deployment unlocks a significant competitive advantage.
You’ll find an AWS CloudFormation template with everything necessary to spin up your own continuous deployment pipeline at the AWS Labs EC2 Container Service – Reference Architecture: Continuous Deployment repo on GitHub. If you have any questions, feedback, or suggestions, please let us know!