What is Continuous Integration?
Continuous Integration is a methodology followed by development teams, where in they submit their codes periodically to a source control management system (SVN, ClearCase, Git etc.). Each time a new submission happens, a set of automated scripts run to build, deploy and test the build. This ensures that the current build is error free and a clean deployment.
There are many tools available for Continous Integration...TeamShip, GitLab, Codeship. The most commonly used one is Jenkins.
I will talk about the most commonly used CI tool, Jenkins.
This is just the tip of the iceberg. There are many advantages that CI brings along:
1. Integrations are automated
The integration process can be completely authomated. Configure your Jenkins to poll the repository on a regular interval. Once the tool detects a check-in, it triggers a set of configured scripts to automatically buils and deploy the build to the server. Thsi saves time and also eliminates manual errors
2. Testing can be automated
Jenkins can be used to trigger a set of automated test cases each time a build is triggered. This ensures that the current build does not break any existing use cases.
3. Early detection of issues
CI can help find the issues before they can appear on the deployed application on the server, thus helping finding issues earlier and causing substancially less damage
4. Time Efficient
You save a lot of time lost due to debugging, manual integration and the deliveries can be done faster
5. Reduces manual work
Equates to saving time, money and less errors due to an authomated process
Features provided by Jenkins:
There are a numerous things that are provided by jenkins, among others
1. Addons: Jenkins can be easily extended by using over 400 plugins that are available.
2. Source Control: Jenkins can directly connect to all major version control systems and can poll periodically for changes. It can also check code back in to the version control
3. Job Configuration History Plugin: Tracks the changes to the job configurations, including who did it.
4. Automation: Schedule automatic builds based on cron expressions
5. Testing: Configure automated test cases to be triggerd on each build. This can trigger an automatic smoke test for each build.
6. Shell Scripting: Can add pre and post build operation by using basic shell scripts.
7. Notifications: Notifications can be configured to be sent to a set of people for the build status.
8. Access Control: The jenkins admin has an elaborate dashboard to provide multiple levels of access to various users.
9. Sequence the jobs: The jobs can be sequenced so that the successful completion of one can trigger another job.
10. Distributed builds: The master slave architecture supports distributed builds. You can build on one server and deploy on another. This reduces the load on the servers
11. Publish various reports: The jenkins plugins can be use to publish various reports in graphical or tabular form, e.g test coverage, code coverage and static code analysis reports.
How to make the best use of CI
Here are some best practices so that the CI features can be used to its best:
1. Maintain a single repository.
2. Make daily check-ins. It is a good practice to check in your code daily and not have any uncommitted code in your local system.
3. Automate the CI job to poll the version control periodically so that build are triggered every time a code is checked in. This way its easier to know which commit has failed the build.
4. Have automated test cases to run for each build to ensure nothing breaks due to a new build.
5. Maintain the unit tests, they can be triggered as a part of the build and verify the build.
6. Publish each build to server, so that the latest build is available for everyone to see.
7. Publish notifications to owners for failed builds, so that actions can be taken quickly.
8. Publish relevant reports. Eg: Test coverage, Code coverage, static code analysis reports etc. A good reports generates confidence to the stakeholders.
This requires commitment from individual team members to commit code frequently and ensure that they do not check in broken and untested code. So this would require to educate and empower the team members.
Adopting the Continuous Integration and Continuous Deployment will help catch the issues early in time and hence reduce risks of errors and ensure better quality.