Repositories
A Repository in Continua is simply a wrapper around an external repository which provides a way for Continua to interact with that repository. Adding a repository to Continua allows the user to make use of that repositories' content in other parts of Continua. For example, adding a repository and assigning it to a Configuration allows that Configuration to use the content in Stages & Actions. Once a repository has been assigned to a Configuration, its change sets are tracked and displayed on various pages. All change sets for a Configuration's repository will be shown on the Configurations change set page. All change sets that trigger a build or were last added since the previous build will be shown on the build's change set page. You also have the ability to see your own change sets if you've linked your Continua account to your repositories' account via the My Changes setting. When configuring a repository, you also have the ability to link it to an Issue Connectors which basically allows you to link certain repository check-ins to an issue in your issue tracking system.
(Something about Global, Project, Config repos????)
Under the hood
Unlike other CI servers like FinalBuidler Server and Hudson, Continua manages the 'getting' of your source code. Primarily this is so that using multiple build agents is quick and safe. You don't need to understand how it works under the hood, but it can be helpful if you're wondering why Continua does things in a certain way.
Caches
Continua maintains several caches of your source code: one on the Server and one of each Agent. When Continua detects a new commit/check-in/changeset in your repository, it updates the Server cache, then each agent updates its cache from the server. This means that, when it's time to run a build the source is most likely already on the Agent.
Building the right codebase
The cache isn't just a bunch of files - it is "version controlled". This makes it easy for us to get the right version of the source to build. For example, lets say you have a Repository Trigger with a quiet period of 1 minute (that is, the build will wait 1 mintue after its triggered to see if any other changes come in). Just after the quiet period has ended, (and the build is just starting) a new change is detected in your repository, which is automatically sync'd to all of the agents. When your build starts running on an agent, it doesn't simply get what's in the cache: it gets the version of the cache that contains the most recent changeset associated with the build. In this case, that will be the changeset that triggered the build.
This also allows us to run stages on different agents. For example, your Build stage might run on Agent1 and your Installer stage on Agent2. When the Installer stage gets to Agent2, it gets the same version of the cache that was used for the Build stage. Without this versioned cache, we would need to run every stage on the same Agent, to ensure that the correct source was build used.
We also re-apply and changes you make to the source during the build. So again, if your Build stage runs on Agent1 and produces a bunch of assemblies, when the Installer stage starts on Agent2 those changes will be re-applied to the source folder, and you can reference them as if you had just build them.
Build workspace and parallel builds
Each build has its own workspace: a directory that is sync'd between the Continua server and any agents the build runs on. It contains things like a serialized copy of the build's variables, any source files that are changed during the build, any artifacts that are registered, and the build log. When a build is run on an agent, the correct version of the source is copied from the cache into the workspace. Using a copy means that we can run multiple builds of the same stage, at the same time, on the same agent without any conflicts.
Although a copy of the source is placed in the workspace on the agent, we don't sync this back to the server. The performance cost of moving a potentially large amount of data around for every build is too high. Instead, as mentioned above, we track files that are changed during the build and re-apply them.
Triggers
A Trigger is a Continua feature that waits for certain events to occur, when they occur the Configuration the trigger is assigned to is executed. A trigger can be setup to execute the Configuration when a check in is made to a specified repository or at a certain period in time.