Problem Statement
To determine the best solution for Continuous Integration/Continuous Deployment in a multi-datacenter environment.
Possible Solutions
Continuous integration: Its the process of automatically building the appropriate environment and testing the software on a every commit. Two most popular CI tools are.
- Travis CI
- Jenkins
Continuous deployment: The process of deployment of updates on the production environment while ensuring high availability and rollover capability in case of failures.
- Spinnaker
- Jenkins Master/Slave
This blog gives a good overview of how CI/CD works in an real time environment https://engineering.quora.com/Continuous-Deployment-at-Quora.
The High Scalability blog has been invaluable in learning more about the real life architecture at tech giants and learn more about the intricacies involved. http://highscalability.com/all-time-favorites/
Solution Evaluations
Travis CI
Travis CI is continuous integration as a service that is free for all open projects on Github. Presently, Airavata’s GitHub repo has Travis CI builds enabled, that is, whenever a pull request is submitted by a developer, Travis CI builds and tests the whole Airavata project using Maven.
Pros:
- No need to create and maintain a our own CI server.
- Very reliable, as it is maintained and supported commercially.
- Easy configuration for build and test.
Cons:
- No fine grained control over the CI/CD pipelines.
- Debugging is slightly difficult.
- Lacks support for Continuous Deployment to OpenStack
Jenkins
Jenkins is an open source automation server which can be used for Continuous Integration. It has numerous plugins which can be used to extend its functionality into a full fledged CI/CD server.
Pros:
- Very popular, with lots of community support.
- Large collection of plugins make it easy to achieve fine grained control over the process.
- Able to create complex pipelines that supports multiple third party Continuous Deployment tools such as Spinnaker .
Cons:
- Have to create and maintain our own Jenkins master server.
- Initial setup and configuration may be time consuming and difficult.
- Lacks the reliability of a maintained service such as Travis .
Spinnaker
Spinnaker is an open source multi-cloud Continuous Delivery platform started by Netflix. It provides a complete CI/CD pipeline when integrated with Jenkins. Its built on the concept of immutable infrastructure, i.e every instance in the cluster can only be destroyed but not altered after it is created.
Pros:
- It has different modern deployment strategies viz blue-green, canary, etc built-in.
- Its concept of immutable infrastructure makes the deployment process very reliable.
Cons:
- Difficult setup and lack of support.
- It freely creates and destroys infrastructure, which might end using a lot of resources.
- Learning curve for new developers.
Conclusion
Though Travis CI provides integrations to cloud providers like AWS, but it lacks support for in-house infrastructure and also OpenStack, hence makes no sense to invest time in Travis CI. Therefore, we recommend Jenkins for accomplishing the CI & CD implementations, especially because of the fine grained controls it provides through Jenkins pipelines and the support for continuous deployments through Jenkins slaves.
Though Spinnaker seems to be full fledged solution, it lack proper documentation and its installation process is difficult. Its concept of constantly creating new instances and destroying old instances may not be suitable for Airavata as we may need to reuse existing reserved instances.Using Jenkins for Continuous Delivery using a master/slave configuration may seem to be the best option.