Hello World executed in almost no time at all. However, the pipelines are usually more complex, and time is spent 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 can we ensure that the builds will run quickly and smoothly?
Jenkins becomes overloaded sooner than it seems. Even in the 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 execution tasks to the Jenkins agents...