Provider
A provider is responsible for managing worker nodes (which may be VMs, real servers, containers, or other resources) for Zuul. A provider may appear in more than one tenant; if it does, it is still treated as a single provider that is shared by those tenants.
The provider may have resource limits applied to it; if it does, those limits are shared across all tenants (in other words, if a provider has a limit of 10 instances, then all of the tenants that use that provider share the 10 instance limit).
Providers refer to other objects, such as Label, Image and, indirectly, Flavor objects. These references are made by name, and since they may be loaded from other projects, it is possible for the same provider to reference different label, flavor, and image objects in different tenants. This will work as expected: the cloud will have different images uploaded if they reference different images, or it will use the same image if they reference the same image.
If there are settings that are common to most or all flavors, images, or labels, they may be able to be added to the associated defaults section (flavor-defaults, label-defaults, and image-defaults). In these cases, a specific setting for an individual flavor, label, or image would override one set as a default. Further, some settings are available on the top-level flavor, label, and image objects; some of these may also be overridden at the provider.
Each provider must inherit from exactly one Section. A section represents a portion of a cloud or other system that supplies resources. Sections may inherit from other sections, but eventually one of them must be associated with one of the Zuul Connections which represent the entire cloud or resource supplier.
Configuration information that is common to multiple providers should be added to to a section rather than the providers. For the most part, sections and providers have the same configuration attributes available to them. The few exceptions are the section attribute which is only available to providers, the connection attribute, which is only available to sections (and may not be overridden in a chain of inheritance of multiple sections), and the flavors attribute, which is only available to sections.
This inheritance chain guarantees that any provider and its associated sections are only ever associated with a single connection and therefore driver (such as AWS, OpenStack, etc.). Because each remote system behaves differently, the options available for each system differ, and therefore the options available to a given provider or section depend on which driver is used for the underlying connection. A small number of very basic options which are available in all cases are documented here, but the full list of available options is provided with each driver’s documentation.