How does Continuous Integration Work
April 17, 2020

How Does Continuous Integration Work?

Continuous Integration
Static Analysis

Continuous Integration (CI) is important. But how does Continuous Integration work?

A CI process is only effective if it has been properly implemented. For that reason, we answer how does Continuous Integration work and provide guidance on how to implement Continuous Integration.

How Does Continuous Integration Work?

Continuous Integration streamlines the software development process, ensuring that there are no disconnected segments. It accomplishes this by including all the stages — integration, testing, verification, and deployment — into each segment of development.

These stages are performed every time a developer commits a change to the repository as well as each time code changes are merged. So, every change is integrated, tested, and verified bringing the project closer to becoming a viable release candidate.

What’s more, Continuous Integration helps to split the burden of code integration for developers into smaller, more manageable tasks. This helps to ensure that big integration problems won’t have the chance to arise, as problems are dealt with individually, early on, and without disrupting other team members.

Implement Quality Gates

Quality gates ensure that only clean, working and tested code makes it into the repository. So, when a developer checks some code into the repository, it goes into a staging repository or some form of locked state, until the verification and validation requirements are met.

If the code passes all the tests, then the commit is transferred to the real repository, unlocked for pull requests, or merged to the main branch as appropriate for the system used.

If the code doesn’t pass all the tests, then the commit remains locked, the developer is notified, and they can take the necessary corrective action before resubmitting the changes for a further check.

How does Continuous Integration work
Example of how Continuous Integration works with quality gates.

Using Nightly Builds

Many organizations use nightly builds for CI. Nightly builds are when the codebase is checked out of the repository at the end of the working day, built, and tested. And the results from this build are examined the next morning and the full set of issues are then shared with the development team.

However, there are some problems with using nightly builds. The main problem is that there is a time lag between checking code in and seeing the results.

For example: A developer may check in some code in the morning that will break the build, but is unaware of that until the next day. By that time, the developer may have moved on to a different task and no longer remembers what the original problem could be.

This leads to more time spent trying to understand the problem, which increases the risk of fixing the problem incorrectly or breaking something else.

Best Practices For Continuous Integration

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9 Steps of Continuous Integration

There are 9 steps to Continuous Integration.

  1. Developers check code into the version control system’s staging repository.
  2. The version control system (VCS) or code repository notifies the CI server that a commit has occurred. Or, the CI server polls the repository periodically looking for commits.
  3. The CI server starts the build process on a build server.
  4. The code containing the latest commit — ideally just the minimum file set — is checked out of the repository into a local workspace on the build server.
  5. The changed code is built, analyzed, and tested.
  6. Important results are reported back to the CI server, along with any important details and files that need to be retained.
  7. The CI server sets the final — Pass / Fail — result of the build.
  8. If the build met the success criteria, then the committed change may proceed through the development cycle - transferred to the real repository or merged to the main development stream. If the build failed, the committed changes are blocked from proceeding until those issues are resolved.
  9. The CI server notifies any parties who have registered interest in the build. They can then log into the CI server to view the status plus any additional information.

How Continuous Integration Systems Work

Automated testing is key to Continuous Integration. Once the test phases have been automated, the CI system can run the appropriate tests and take action on the results. That is why a CI system can be thought of as a sophisticated program that schedules, launches compilations, packages, and tests processes.

The five core requirements of a CI system are the ability to automatically:

  1. Detect code that has been committed either by monitoring the repository for commits or accepting some external stimulus — usually from the source code repository.
  2. Checkout code from the repository onto a machine equipped with all the necessary build and testing tools available.
  3. Build the code.
  4. Run all the tests on the resulting executable(s).
  5. Report the results of the build and test to the appropriate team member(s).

Home-Grown CI Systems

Continuous Integration automation can be accomplished with some scripting and command line tools. And, many companies have traditionally started off with this type of setup.

However, administering these scripts can often become a full-time responsibility that draws developers away from their core task of writing code. What’s more, this can also complicate the readability and understanding of the development processes.

CI platforms, such as Jenkins, provide a centralized and standardized base from which to work. And the output of these projects and builds are then available to the whole team, and not just the developers.

Even higher-level management would probably like to know if the number of tests passed today was greater than the number of tests passed last week.

CI using Jenkins

Jenkins is a popular CI system. It is customizable (with countless plugins) and scalable. That’s why Perforce tools come with Jenkins plug-ins for version control and static code analysis.

How Continuous Integration Works With Static Analysis

Klocwork is the ideal static analyzer to support Continuous Integration, and its unique Differential Analysis technology provides the fastest analysis results for CI pipelines. What’s more, by using Klocwork, you are able to:

  • Ensure complex software is safe, secure, and reliable.
  • Reduce the cost of finding and fixing defects earlier in development.
  • Prove compliance by enforcing software coding standards.
  • Improve developer productivity, testing efforts, and velocity of software delivery.
  • Report on quality over time and across product versions.

See how your Continuous Integration process can benefit from Klocwork. Sign up for our next live demo to see for yourself how Klocwork improves CI.

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