Continuous Integration with TeamCity
What is Continuous Integration?
Continuous Integration is a software development practice in which developers commit code changes into a shared repository several times a day. Each commit is followed by an automated build to ensure that new changes integrate well into the existing code base and to detect problems early.
To learn more about continuous integration basics, refer to Martin Fowler's article.
What is TeamCity?
JetBrains TeamCity is a user-friendly continuous integration (CI) server for developers and build engineers free of charge with the Professional Server License and easy to set up!
This video gives a general overview of the main TeamCity features and explains the licensing policy:
What can you do with TeamCity?
Run parallel builds simultaneously on different platforms and environments
Optimize the code integration cycle and be sure you never get broken code in the repository
Review on-the-fly test results reporting with intelligent tests reordering
Run code coverage and duplicates finder for Java and .NET
Customize statistics on build duration, success rate, code quality, and custom metrics
and much more.
To learn more about major TeamCity features, refer to the official JetBrains site.
TeamCity works great not only for admins and build engineers, but also for developers. Watch this video to see some of the signature features it provides:
The complete list of supported platforms and environments can be found here.
Basic TeamCity concepts
This section explains the main concepts. The complete list can be found here.
The TeamCity build system comprises a server and Build Agents.
A piece of software that actually executes a build process. It is installed and configured separately from the TeamCity server, i.e. the agent can be installed on a separate machine (physical or virtual, and it can run the same operating system (OS) as the server or a different OS. Build Agents in TeamCity can have different platforms, operating systems, and preconfigured environments that you may want to test your software on. Different types of tests can be run under different platforms simultaneously so the developers get faster feedback and more reliable testing results.
The server itself does not run either builds or tests: the server's job is to monitor all the connected build agents, distribute queued builds to the agents based on compatibility requirements, and report the results. All information on the build results (build history and all the build-associated data except for artifacts and build logs), VCS changes, agents, build queue, user accounts and user permissions, etc. are stored in a database.
A TeamCity Project corresponds to a software project or a specific version/release of a software project. A project is a collection of build configurations.
A combination of settings defining a build procedure. The settings include VCS Roots, Build Steps, Build Triggers described below.
A collection of version control settings (paths to sources, username, password, checkout mode and other settings) that defines how TeamCity communicates with a version control (SCM) system to monitor changes and get sources for a build.
A task to be executed. Each build step is represented by a build runner providing integration with a specific build tool (like Ant, Gradle, MSBuild, etc), a testing framework (e.g. NUnit), or a code analysis engine. Thus, in a single build you can have several steps and sequentially invoke test tools, code coverage, and, for instance, compile your project.
Any modification of the source code which you introduce. If a change has been committed to the version control system, but not yet included in a build, it is considered pending for a certain build configuration.
Refers to both: the actual process of creating an application version and the version itself. After the build process is triggered, it is put into the build queue and is started when there are agents available to run it. After the build is finished, the build agent sends Build Artifacts to the server.
A list of builds that were triggered and are waiting to be started. TeamCity will distribute them to compatible build agents as soon as the agents become idle. A queued build is assigned to an agent at the moment when it is started on the agent; no preassignment is made while the build is waiting in the build queue.
Files produced by a build, for example, installers, WAR files, reports, log files, etc, when they become available for download.
Basic CI Workflow in TeamCity
To understand the data flow between the server and the agents, what is passed to the agents, how and when TeamCity gets the results, let's take a look at a simple build lifecycle.
The TeamCity server detects a change in your VCS Root and stores it in the database.
The build trigger sees the change in the database and adds a build to the queue.
The server finds an idle compatible build agent and assigns the queued build to this agent.
The agent executes the Build Steps. While the build steps are being executed, the build agent reports the build progress to the TeamCity server sending all the log messages, test reports, code coverage results, etc. to the server on the fly, so you can monitor the build process in real time.
After finishing the build, the build agent sends Build Artifacts to the server.
Now you can proceed with TeamCity installation.