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Continuous Integration – CI
Continuous Integration (CI) is a software development practice where team members integrate their coding work frequently into the collective software code, typically leading to multiple integrations of the software project daily. Each integration is verified by an automated build, including a test, to detect integration errors as quickly as possible.
This approach was first introduced as a part of Extreme Programming (XP) methodologies but has now evolved as a fundamental practice in various Agile software development processes.
The main aim of CI is to prevent integration problems. Instead of building features in isolation and integrating them at the end of a development cycle, which is often time-consuming and risky, CI proposes to integrate early and often to avoid the pitfalls of ‘integration hell’.
The key benefits include reducing code integration problems and enabling fast software delivery. Integrating regularly lets you detect and locate errors more quickly and easily.
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Key Elements of Continuous Integration
CI practice relies heavily on automation.
When a developer pushes changes to the code repository, a series of automated events occur – building the code by taking the source code text and converting it into runnable software, running unit and integration tests with the program, and deploying the new software in a staging environment.
This quick feedback loop is what makes CI highly effective. The key elements include:
- A version control system.
- A build and integration process.
- An automated testing suite.
- A feedback mechanism for reporting the state of the software.
CI Tools and Technologies
Several tools support continuous integration, including Jenkins, Travis CI, CircleCI, and GitLab CI. These tools monitor the repository and execute events or pipelines when changes are detected.
The pipeline typically includes building the code, running tests, and providing reports. Depending on the project’s complexity, this process could also include deploying the software into a production-like environment, running additional tests, and giving feedback to the team.
Best Practices in Continuous Integration
Successful implementation of CI requires following certain best practices. Some of these include:
- committing code to the main branch regularly (preferably daily),
- having a build process that’s automated and fast,
- making sure the test suite covers enough of the codebase, and
- maintaining a culture of fixing issues immediately when a build fails.
In a CI environment, it’s crucial to keep the build passing at all times. If a test fails, the highest priority becomes fixing the build.
Continuous Integration in DevOps
Continuous integration is a critical element in modern DevOps practices. It forms the foundation of Continuous Delivery (CD) and Continuous Deployment (CD), where each integration is automatically deployed to a staging or production environment after the automated tests are passed.
This culture, automation, and set of practices aim to improve software releases’ speed, efficiency, and quality.
Origins of Continuous Integration
The concept of Continuous Integration was one of the original twelve practices of Extreme Programming (XP), a software development framework that was part of the broader agile movement in the 1990s. At that time, software development typically involved long, separate phases of development, testing, and integration, which often led to multiple issues when trying to combine different parts of a system.
The XP methodology proposed more frequent integration to help minimize these problems. Martin Fowler and Kent Beck, among others, then popularized this idea of Continuous Integration.
It has since been adopted outside of XP and is now integral to many Agile and DevOps methodologies.
Evolution of CI Tools
Over the years, tools for supporting Continuous Integration have evolved significantly. The early CI processes often involved manually invoking build scripts and running tests.
Then came standalone CI servers like CruiseControl, one of the first open-source CI tools to automate this process.
The next-generation CI tools included Jenkins (originally a fork of Hudson, another CI server), Bamboo, and TeamCity. These tools provided a more user-friendly interface, configuration options, and plug-in ecosystems.
More recently, hosted CI solutions have gained popularity. Travis CI, CircleCI, and GitLab CI/CD are among them. These tools have integrated the whole software development process into one platform and are often provided as a service, eliminating the need for teams to maintain their CI servers.
Future Trends
As we move forward, CI increasingly intertwines with practices like Continuous Delivery, Continuous Deployment, and DevOps. Moreover, CI/CD practices are expanding beyond just traditional software applications.
They’re now being used in areas such as data science to maintain reproducibility and efficiency in machine learning projects or infrastructure management (Infrastructure as Code), among others.
This trend will continue as more areas see the benefits of applying CI practices.
What is Continuous Integration? – 6 mins
