Jenkins architecture

The hello world job executed in almost no time at all. However, the pipelines are usually more complex and spend time on tasks such as downloading files from the internet, compiling the source code, or running tests. One build can take from minutes to hours.

In common scenarios, there are also many concurrent pipelines. Usually, the whole team, or even the whole organization, uses the same Jenkins instance. How to ensure that the builds will run quickly and smoothly?

Master and slaves

Jenkins becomes overloaded sooner than it seems. Even in case of a small (micro) service, the build can take a few minutes. That means that one team committing frequently can easily kill the Jenkins instance.

For that reason, unless the project is really small, Jenkins should not execute builds at all, but delegate them to the slave (agent) instances. To be precise, the Jenkins we're currently running is called the Jenkins master and it can delegate to the Jenkins agents.

Let's look at the diagram...