Continuous Delivery | What it is and How Does it Work?

Continuous Delivery (CD) is a practice in software development for automating and improving the efficiency of new code deliveries to production. In simpler words, it focuses on enabling software release reliably at any time using an automated set of tests and validation steps. The key idea is that the code should be kept in a deployable state throughout its life cycle. 

It is a development practice that allows teams to integrate changes in the shared repository frequently by automating the build and test process, hence easily uncovering problems at an early stage. Faster iterations mean higher quality and more frequent releases, hence higher customer satisfaction and reduced time-to-market. 

Continuous Delivery, with the help of Continuous Integration and CI/CD testing, helps you build the perfect development and deployment pipelines.

In this guide, let’s discuss more on why is Continuous Delivery needed especially in today’s Agile development practices, discussing how to implement CD and the best tools for implementing continuous delivery processes.

What is Continuous Delivery in Testing?

Continuous delivery in testing means automating the process of testing and integration into a development pipeline. This ensures that every change introduced into the code is carefully and automatically tested before deployment. It accelerates feedback and ensures high software and frequent releases.

1. Automated Testing: Involves implementing unit, integration, and system tests to catch issues very early.

2. Continuous Feedback: Feedback on the quality and functionality of the code is delivered quickly.
3. Seamless Integration: Integrates testing into the build process so that it runs smoothly.
4. Defect Detection: It quickly detects any bugs and hence reduces time-to-fix. 
5. Release Confidence: Ensures a high-quality, reliable release that’s production-ready.

Why Continuous Delivery?

Continuous delivery is a development practice for software whereby one builds, tests, and releases frequent and reliable developments. It extends the concept of continuous integration through the automation of deployment processes to all environments while ensuring that the software always remains in a deployable state.

1. Faster time to market: It makes the process of releasing new features and bug fixes so easy that enterprises can respond very quickly to any change in the market or to customer demand.
2. Better Quality: Automated testing and rigorous validation at each stage of the pipeline now allow you to detect and resolve problems in the very early stages of development.
3. Lower Risk: It reduces the risks involved in deployments. Since it breaks the deployment process into tiny, manageable pieces, the identification and isolation of issues becomes easier.
4. More efficient: Automation of build, test, and deployment will free developers’ time to concentrate on new features rather than mundane tasks.
5. Greater Collaboration: It enables teams from development, operations, and quality assurance to collaborate more.
6. Higher Customer Satisfaction: The frequent and reliable updating of software leads to increased customer satisfaction since customers experience little or no disruption and receive the latest features. 
7. Competitive Advantage: Fast and better-quality software will enable the best chances for the organization to compete within a market.

Check here – Benefits of Continuous Integration

What is an Example of Continuous Delivery?

Imagine a mobile commerce application developed by a software team. Following are the steps that would be needed to ensure a smooth continuous delivery process.

1. Code Commit: A developer changes the code of the app, for example, by adding a new product category, and then commits that code into a versioning system such as Git.
2. Build: A CI/CD tool like Jenkins, CircleCI, or even GitLab CI/CD performs a build process where the code is compiled as an executable application package – for example .apk for Android, or .jar for Java.
3. Unit Testing: Automated unit testing, using testing tools like JUnit or Jest, allows running executable tests that cover individual components of the code to validate their functionality.
4. Integration Testing: This is the phase where a testing tool such as Testsigma, Selenium, or Appium will be used to test how all of the components of the app interact in a test environment.

5. UI Testing: This is the automation of UI tests using any UI testing framework like Testsigma or Selenium to ensure that the User Interface part of the App meets expectations.
6. Performance testing: This type of testing measures the behavior of an app under various conditions imposed on it using tools such as JMeter or Gatling.
7. Deployment to Staging: The application built is then deployed into a staging environment with deployment tools like Ansible, Puppet, or Chef.
8. Deploy to Production: Once approved, the app is automatically deployed to production with deployment tools like Ansible, Puppet, or Chef. 

In the process, continuous feedback from the CI/CD pipeline enables the team to identify and fix issues early in the development cycle.

Note: This is the simplest possible example. Real-life CI/CD pipelines often include complex steps for security testing, A/B testing, canary deployments, and so on, and they are likely using other tools like Docker for containerization and Kubernetes for orchestration.

Check here – Canary Testing

Who should do Continuous Delivery and When?

Continuous delivery is best for teams and organizations that consider speed, quality, and customer satisfaction as paramount. It’s particularly suited for:

1. Software-centric businesses: These are businesses whose core products or services are software applications such as tech startups, e-commerce platforms, and SaaS providers.
2. Teams that deploy frequently: Any organization that deploys software updates as often as daily, weekly, or biweekly.
3. Organizations with high customer expectations: Firms working in competitive markets with a need to deliver new features or bug fixes at breakneck speed.

When to Adopt Continuous Delivery?

1. Early in the development lifecycle: Integrate CD at the beginning of a project to establish a strong foundation for automatic and smooth delivery.
2. When transitioning from waterfall to agile: CD will normally fit very well with agile development methodologies that are also iterative and incremental.
3. To address release bottlenecks: If an organization is struggling with slow and error-prone release processes, CD can help streamline the process and reduce risks. 
4. To improve software quality: Continuous delivery identifies and fixes defects earlier in the development cycle through automated testing and deployment, hence yielding high-quality software. 

While Continuous Delivery offers a huge number of benefits, it requires cultural change and huge investment in tools and infrastructure. Any organization should assess precisely its degree of readiness and capabilities before starting to implement CD.

How does Continuous Delivery Work?

To understand how continuous delivery works, we need to identify the pain points in a development and deployment lifecycle and understand how CI/CD processes solve those problems. Let’s look at a complete end-to-end workflow of a CI/CD pipeline and understand how Continuous delivery in conjunction with Continuous integration helps you build the vest deployment workflow. Below are the steps in a Continuous Delivery Pipeline.

Step 1. Code Commit

Developers write new code or tune existing ones and commit these changes to a version control system like Git. That is the event that triggers a CD pipeline. Through version control, one keeps records of the changes made in their code. This way, teams can collaborate, roll back, and efficiently manage their code.

Step 2. Build Application Packages

Whether it be Jenkins, CircleCI, or GitLab CI/CD, a CI/CD tool at this stage will compile the code into a deployable artifact. This could be in the form of WAR, JAR, or a Docker image. The reason for doing this is to ensure that the source code is turned into a form ready for deployment. Building the code regularly helps in the preservation of code integrity and avoids environment-based problems.

Step 3. Unit Testing

This involves running automated unit tests to check whether the individual components of any piece of code are functioning correctly. This is an important process in identifying the defects at an early stage of the development cycle and in attaining code quality without regressions. By catching issues at the unit level, developers can fast-track problems and fix them right away without affecting other parts of the application.

Step 4. Integration Testing

Integration tests validate how different components of the application work among themselves. This step ensures that the application works as it’s supposed to whenever different parts interact. Early identification of integration issues helps teams avoid big problems later in the development process.

Step 5. Code Quality Checks

Static code analysis tools like Sonar, Snyk, etc. are used to evaluate the quality of the code, find problems, and apply coding standards. This is done to maintain code readability, maintainability, and security. Coding standards improve collaboration in code and increase the guarantee that there will not be vulnerabilities in it.

Step 6. Containerization (Optional)

Optionally, the application may be Containerised. Containers provide a uniform and independent environment beyond the application, which makes it easy to implement and maintain distinct versions within different environments. Containerization promotes both portability and scalability but ensures efficient resource utilization.

Step 7. Deploy To Staging

The artifact built is then pushed to a staging environment, very much like your production environment. This allows for final testing/validation before releasing the application to the end users. Testing in staging allows teams to find problems and fix them without impacting production users.

Step 8. Performance Testing

Performance tests should be run in the staging environment to check response times, scalability of the application, and resource usage. This step helps isolate performance bottlenecks and enhances the production application.

Step 9. Security Testing

Security scanning is the process of identification of vulnerabilities within the application. Risks can be detected early, and teams will want to protect both the application and user data from any dangers. 

Step 10. Deployment to Production

Once the application has passed all tests and approvals, it is then automatically deployed to production. This delivers the application into the hands of end-users. Automation in deployment minimizes the potential for human error and assures uniformity in deployments. 

Step 11. Monitoring and Logging

The performance and health of the application are tracked continuously in the production environment. Teams will be able to pick up issues quickly, find the root cause of an issue, and resolve it much more effectively if they can collect and analyze logs for optimizing an application’s performance and user experience.

Check here – Devops vs CI/CD

Continuous Delivery Pipeline: The 5 Stages Explained

As discussed, a Continuous Delivery pipeline is an automated process through which software moves from development to production. It consists of a series of stages, each with different tasks and goals through which it passes. In other words, this pipeline ensures that software is always in a deployable state; hence, frequent release cycles can be done on-demand which increases software quality.

Stage 1: Develop

The development stage is the foundational phase of the CD pipeline. This stage creates and refines a software product for the first time. Developers write, test, and then refine code in iterative cycles to bring functional software components into existence. A primary objective is to come up with quality code that meets all requirements stipulated in the project. It pawns over to creating, editing, and enhancing a code base by developers jointly.

Effective communication and reviewing codes at this stage are important to ensure the quality and consistency of the code. Developers make use of version control systems to track down changes to the code, collaborate effectively, and manage other versions of the code.

Steps Involved in the Develop Stage are:

1. Write and refactor code based on the user stories or requirements.
2. Conduct thorough unit tests to ensure code correctness.
3. Collaborate with team members through code reviews.
4. Commit changes to a version control system such as Git. 
5. Manage different code versions and branches.

Example: A developer creates a new product page component for the shopping website and writes HTML, CSS, and JavaScript code. Unit testing is done to ensure that the component is displayed correctly and all prices are calculated accurately. After the code review, the developer commits these changes to the Git repository and is working on a new branch for the feature.

Stage 2: Build

The next stage in the CD pipeline is the Build stage. It is where source code, in a human-readable form, gets converted to a deployable artifact. This step consists of compiling, assembling, and packaging the code into a format deployable in a production environment; for example, a JAR, WAR, or Docker image. The build process is automated to ensure consistency and repeatability.

Essentially, a build resolves dependencies, compiles source code into executable code, and creates all necessary artifacts. A reliable and efficient build process is important for the quickening of the delivery pipeline.

Major Steps Involved in the Build Process:

1. Get code from the version control
2. Compile source code into an executable binary format.
3. Package the application into deployable artifacts.
4. Resolve Dependencies and libraries
5. Create needed build artifacts; for example, JAR and WAR. 

Example: The CI/CD tool automatically pulls the new product page component code from the Git repository. On compilation of the code and its dependencies, it packages it into a WAR file ready to be deployed in an application server.

Stage 3: Test

The Test stage is vital in securing the quality of software with the help of continuous testing. This will involve running different tests on the build artifact to check that all is well and it works according to expectations. Included are unit tests, integration tests, and other test categories like performance and security testing if required. Automation is key to efficient and complete testing.

Early testing helps in tracing out defects in the development cycle before it reaches production. Automation testing allows teams to increase test coverage and lower regression risk.

Here’s the best continuous testing strategy that you can adopt for seamless automated testing of your pipeline code.

Major Steps Involved in the Test Stage:

1. Run unit tests
2. Conduct integration tests
3. Run UI tests

4. Run security scans
5. Generate test reports

Example: Triggering the CI/CD pipeline to run the unit tests ensures that the development of the new product page component is functional. Run integration tests to see that the component interacts correctly with the rest of the e-commerce website. UI tests validate user experience for the new product page.

Stage 4: Deploy

In the Deploy stage, we migrate the build artifact, which has now been successfully tested and validated, into production or staging environments. This entire step details moving an application to production, configuring its settings, and making it user accessible. Automation can contribute a lot here to smooth out this process and reduce human errors.

The deployment strategies could range in complexity from simple to complex based on the use case application and risk tolerance. Common strategies in this space include blue-green deployments, canary releases, and rolling updates. One can make use of the “Infrastructure as Code” tools for infrastructure provisioning and configuration in consistent deployments.

Major Steps Involved in the Deployment Stage:

1. Package application for deployment.
2. Deploy to target environment; staging or production.
3. Set environment-specific configurations.
4. Start application services.
5. Validate deployment success.

Example: After the WAR file has been built, it is deployed into the staging environment – which is an identical replica of the production environment. It is here that database connections and application servers get configured against the staging environment. The application is started and automated tests are run to verify correctness, pointing to the deployment.

Stage 5: Release

The Release stage is the final CD pipeline stage where the software is released for end-user consumption. In other words, this means deployment into the production environment and consequently managing its lifecycle. This critical stage must therefore be very well planned and executed to reduce disruptions and ensure a smooth user experience.

Feature flags, canary releases, and A/B testing are typical approaches used in the release stage to progressively roll out new functionality to users for feedback. Monitoring and logging are necessary for assurance about the performance of the application and for identifying problems.

Major Steps Involved in the Release Stage:

1. Deploy to production environments.
2. Monitor application performance.
3. Implement feature flags.
4. Conduct A/B testing.
5. Gather feedback from the user. 

Example: The approved WAR file is then promoted to the production environment. The new product page is initially released to a ridiculously small fraction of users, monitoring its performance and obtaining feedback from them; this is called a canary release. Feature flags control the visibility of the new product page. KPIs are tracked which quantify how the new feature changed users’ behavior in general and sales in particular.

Check here – Release Management

Conclusion

To sum up, a Continuous Delivery pipeline is one of the cornerstones of modern software development, automating the journey from code to production. It empowers teams to deliver software faster with higher quality and reduced risk by seamlessly linking development, build, test, deploy, and release stages. This is a collaborative model promoting a culture of continuous improvement that lets organizations keep up with changing market demands and deliver exceptional customer experiences.