jenkins

Pipeline as code moved the build definition into the repository, where it is reviewed and versioned with the thing it builds. Declarative is the default answer, and knowing when scripted still earns its place is the follow-up.

Jenkins is mostly plugins, they have a dependency graph nobody drew, and the controller is a single point of failure for every team. The answer is a rehearsal against a copy of production, not a maintenance window and hope.

Distinguish executor capacity, placement and provisioning failures, then size an agent pool from measured resource use and cleanup behaviour.