Label

A label is used by Provider objects to configure the operational characteristics of worker nodes. Unlike Flavor or Image objects, a label does not correspond to any existing concept in a cloud. Instead, a label incorporates the settings controlled by images and flavors by reference, and adds some other operational settings to complete the information needed to launch a worker node.

Jobs request worker nodes by using labels, and labels, along with the images and flavors they reference, are used by providers to determine what nodes to provide.

Every label has a reference to a single flavor and a single image. That reference is by name, which means that a given label always references the same flavor and image. Within a single tenant, all providers with a label will reference the same flavor and image objects. But different tenants may have different definitions of flavors and images with the same names, so even if multiple tenants include the same label objects, those objects may reference different flavor and image objects.

The standalone label configuration object itself is where the flavor and image objects are referenced. Some other globally-applicable options for the label are also available. More options become available when the label is attached to a Section or Provider object. See the driver-specific provider options for details.

For example, a user might decide to use a small vm running the latest version of Debian for launching worker nodes. They would then define a label object that references pre-existing image and flavor objects:

- label:
    name: small-debian-vm
    description: A very small VM for running simple tests on Debian.
    image: debian-latest
    flavor: small-vm

That expresses the idea of a label that runs Debian on a small VM, but it doesn’t contain any of the necessary information to actually launch that VM in a cloud. When the label is attached to a provider, the associated flavor and images will also need to be attached. Once all three are attached, the provider will have enough information to create the requested VM.

The attributes available to top-level label objects are:

label

label.name (required) Type: str: The name of the label. Used to refer to the label in Zuul configuration.

label.description Type: str: A textual description of the label.

label.image (required) Type: str: The name of the Image to use with this label.

label.flavor (required) Type: str: The name of the Flavor to use with this label.

label.max-age Default: 0 Type: int: The time (in seconds) since creation that a node may be available for use. Ready nodes older than this time will be deleted.

label.max-ready-age Default: 0 Type: int: The time (in seconds) an unassigned node should stay in ready state.

label.min-ready (required) Type: int: Minimum number of instances that should be in a ready state. Zuul always creates more nodes as necessary in response to demand, but setting min-ready can speed processing by attempting to keep nodes on-hand and ready for immedate use. This is best-effort based on available capacity and is not a guaranteed allocation. The default of 0 means that Zuul will only create nodes of this label when there is demand.

label.min-retention-time Default: 0 Type: int

The time (in seconds) since an instance was launched, during which a node will not be deleted. For node resources with minimum billing times, this can be used to ensure that the instance is retained for at least the minimum billing interval.

This setting takes precedence over max-[ready-]age.