As many companies have, my current employer has acquired a number of other companies and tried to integrate their technologies and employees into the fold.
Of course, the release processes are completely different. At first, I did not try to merge the different processes, but developers were starting to cross "company boundaries". I decided to create a new theory of process for the developers.
The release process is broken into four components:
- build
- distribution/packaging
- installation
- deployment
Build
The build step is the traditional build of software, but for qa and production, as an isolated build process within a standardized, controlled environment. The developer environment is too fluid and unstable to be used for releases. The production build environment should be separate and only accessible to the release engineers. This helps prevent unknowns from being introduced into the release process. The build is performed on a build host often within a revision controlled work area ("sandbox").
Additionally, QA/Prod builds are to be made from tagged code. This allows for reproducibility. This implies that builds do not perform code management/version control. Version control should not be managed by build scripts (exception being CruiseControl-like systems for automated testing based on code changes).
For some code bases, there will be nothing to build, e.g. only perl or php modules. In this case, the build step would be empty, but would still exist.
Distribution/packaging
This step will copy deliverables into a presentable directory structure for the intended target platform or environment (Windows vs. Linux, JDK 1.4 vs. JDK 1.5, and eng vs. qa vs. prod). There may be different environment sets and multiple options. As examples, environments for eng, qa, and production, options for load testing, regression testing or CruiseControl, selecting different database engines.
Build scripts (Makefile, build.xml, maven.xml) may represent the different options and environments by separate targets, variables or options. The build scripts would select the configuration files, libraries or executables to be "shipped".
The distribution step will also package the project for installation at a later time. It will not copy outside of the release engineering environment. Note that this is not packaging of jar/war/ear files – that should be part of the build process.
The purpose of the distribution step is to select proper files, position them, and then package them for later installation.
If there is no need for changes and no need to package deliverables (one file being delivered), then there is no need for this step. Distribution occurs on the build host often within the sandbox (local revision control work area).
In a practical matter, there may be two "targets" for this step: "distribution" and "packaging". Distribution should precede packaging in the process.
Installation
Installation is the traditional step to create a copy of a software distribution and make it available for execution or deployment. There is no distinction between environments; the previous distribution step should have handled that. This step is solely to take a packaged copy of the built project and install it on a machine or machines. Any pre-execution, pre-deployment steps that need to be made are executed here. For example, creation of directories, setting of permissions, changes to databases.
Installation will most often occur on a different machine from the build host and outside of the sandbox. An installation will likely not have targets in the build scripts, unless a build script gets packaged with the application to be used as an install script.
Deployment
Deployment is the activation of the software on the installation machine. This could be deploying a servlet to Tomcat/JBoss, adding a cron job or starting a daemon that has been installed with a startup script or some other means.
After the software has been installed on a machine, the code is deployed from the installation point to the appropriate application server.
