About Zuul

Zuul is a Project Gating System. That’s like a CI or CD system, but the focus is on testing the future state of code repositories.

A gating system doesn’t just test a proposed change; it tests the proposed future state of multiple branches and repositories with any number of in-flight changes and their dependencies. And the same playbooks used to test software can also be used to deploy it.

Zuul itself is a service which listens to events from various code review systems, executes jobs based on those events, and reports the results back to the code review system. The primary interface for Zuul is the code review system (or systems) so that it fits seamlessly into developer workflows, and a web interface is available for inspecting the current status and browsing build results.

The best way to run Zuul is with a single installation serving as many projects or groups as possible. It is a multi-tenant application that is able to provide as much or as little separation between projects as desired.

Zuul works with a wide range of code review systems, and can work with multiple systems (including integrating projects on different systems) simultaneously. See Drivers for a complete list.

Zuul uses a separate component called Nodepool to provide the resources to run jobs. Nodepool works with several cloud providers as well as statically defined nodes (again, simultaneously).

Because Zuul is designed from the ground up to run jobs in a multi-node environment (whether those nodes are bare metal machines, VMs, Kubernetes clusters, or containers), Zuul’s job definition language needs to support orchestrating tasks on multiple nodes. Zuul uses Ansible for this. Ansible is well-known and easy to learn and use. Some existing Ansible playbooks and roles may be able to be used directly with Zuul (but some restrictions apply, so not all will).

However, knowledge or use of Ansible is not required for Zuul – it is quite simple for Zuul’s embedded Ansible to run any shell script or any other program. Zuul’s library of standard jobs even includes a job that will run a specified shell script, so it’s possible to use Zuul without writing any Ansible at all.

Zuul is an open source project developed and maintained by a community of users. We welcome your support and contribution.

Nodepool: https://zuul-ci.org/docs/nodepool/