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An important concept of DevOps is the Continuous Integration (CI) of software. This article addresses the usefulness and necessity of CI.
Set of files with the same tag (e.g., for release).
Branching is a technique that makes a copy of the source code to create two versions that are developed separately. After these branches have been altered by the developers, they are reassembled by a merge. There are various forms of branching. Therefore, a DevOps team must make a choice. This choice is also called the branching strategy.
Commit, Release of the Checked out Source Code.
Creating a work copy.
Central storage of files and history of files.
A marker, often used to indicate a version or release in several items in the repository.
A set of files from the repository (also baseline or mainline).
Continuous Integration provides best practices to allow many programmers to run an application at a time, combining the source code, verified (static test cases), compiled and tested (dynamic test cases) at high frequency.
CI is first mentioned by Grady Booch. Then it was adopted by extreme programming. CI intends to merge source code from programmers into a shared mainline. XP proposes to integrate several times during a day. The goal is to prevent integration problems.
CI is an elastic concept. The word “continuous” is generally interpreted differently. This concerns mainly the frequency of check-in:
In addition, there is another phenomenon that is inconsistent with CI and that is branching. As long as the branch is shorter than the CI frequency, the damage is still limited. But actually, any DevOps team that is doing branching is not busy with CI. An exception could still be release branching (also see article DevOps branching).
This article addresses the following aspects of CI:
Figure 1 shows an overview of CI. The lifecycle starts at the source code that is stored in the source code repository, also called S-CMDB. Normally version management is included in a source code repository tool. The source codes to be used for a build are provided with a release tag. Based on these tags, an export is done and the build server can complete the compilation. Once the object code is created, the software can be tested with the created unit test cases. After generating the documents from the repository and / or source code, the object code is stored in the DML.
| Level | Level definition | Level characteristics | Build management and CI |
| 3 | Optimizing | Focus on process improvement | Teams regularly meet to discuss integration problem and resolve them with automation, faster feedback, and better visibility. |
| 2 | Quantitatively managed | Process measured and controlled | Build metrics gathered, made visible, and acted on. Build are not left broken. |
| 1 | Consistent | Automated processes applied across whole application lifecycle | Automated build and test cycle every time a change is committed. Dependencies managed. Re-use of scripts and tools |
| 0 | Repeatable | Process documented and partly automated | Regular automated build and testing. Any build can be re-created from source control using automated process |
| -1 | Regressive | Process unrepeatable, poorly controlled, and reactive | Manual process for building software. No management of artefacts and reports |
Table 1, CI maturity (www.devopsguys.com).
| Level | Level definition | Level characteristics |
| -1 | Regressive | The following improvements must be made to reach Level 0.
|
| 0 | Repeatable | The following improvements must be made to reach Level 1.
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| 1 | Consistent | The following improvements must be made to level 2.
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| 2 | Quantitatively managed | The following improvements must be made to reach level 3.
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| 3 | Optimizing | The following steps must be taken to stay at level 3.
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Table 2, CI maturity growth path.
There are many tools that can be used at CI. Examples are:
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DevOps Best Practices, ISBN: 9789492618078
Agile Service Management with Scrum, ISBN: 9789071501807
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