nodepool/doc/source/metastatic.rst

zuul

Metastatic Driver

This driver uses NodePool nodes (from any driver) as backing nodes to further allocate "static-like" nodes for end use.

A typical use case is to be able to request a large node (a backing node) from a cloud provider, and then divide that node up into smaller nodes that are actually used (requested nodes). A backing node can support one or more requested nodes, and backing nodes are scaled up or down as necessary based on the number of requested nodes.

The name is derived from the nodes it provides (which are like "static" nodes) and the fact that the backing nodes come from NodePool itself, which is "meta".

providers.[metastatic]

A metastatic provider's resources are partitioned into groups called pools, and within a pool, the node types which are to be made available are listed.

Note

For documentation purposes the option names are prefixed providers.[metastatic] to disambiguate from other drivers, but [metastatic] is not required in the configuration (e.g. below providers.[metastatic].pools refers to the pools key in the providers section when the metastatic driver is selected).

Example:

providers:
  - name: meta-provider
    driver: metastatic
    pools:
      - name: main
        max-servers: 10
        labels:
          - name: small-node
            backing-label: large-node
            max-parallel-jobs: 2
            grace-time: 600

name

A unique name for this provider configuration.

pools

A pool defines a group of resources from the provider. Each pool has a maximum number of nodes which can be launched from it, along with a number of attributes that characterize the use of the backing nodes.

name

A unique name within the provider for this pool of resources.

priority

The priority of this provider pool (a lesser number is a higher priority). Nodepool launchers will yield requests to other provider pools with a higher priority as long as they are not paused. This means that in general, higher priority pools will reach quota first before lower priority pools begin to be used.

This setting may be specified at the provider level in order to apply to all pools within that provider, or it can be overridden here for a specific pool.

node-attributes

A dictionary of key-value pairs that will be stored with the node data in ZooKeeper. The keys and values can be any arbitrary string.

The metastatic driver will automatically use the values supplied by the backing node as default values. Any values specified here for top-level dictionary keys will override those supplied by the backing node.

max-servers

Maximum number of servers spawnable from this pool. This can be used to limit the number of servers. If not defined nodepool can create as many servers that the backing node providers support.

labels

Each entry in a pool's labels section indicates that the corresponding label is available for use in this pool.

labels:
  - name: small-node
    backing-label: large-node
    max-parallel-jobs: 2
    grace-time: 600

Each entry is a dictionary with the following keys:

name

Identifier for this label.

backing-label

Refers to the name of a different label in Nodepool which will be used to supply the backing nodes for requests of this label.

max-parallel-jobs

The number of jobs that can run in parallel on a single backing node.

grace-time

When all requested nodes which were assigned to a backing node have been deleted, the backing node itself is eligible for deletion. In order to reduce churn, NodePool will wait a certain amount of time after the last requested node is deleted to see if new requests arrive for this label before deleting the backing node. Set this value to the amount of time in seconds to wait.