pkg/asset/machines/worker: Default to MachineSets only where we need …

…them

And not for additional zones.  This will keep us from consuming more
NAT gateways and associated EIPs than we need, once subsequent work
ties those resources to Machine(Set) consumption.  This means that
pools where replicas is unset or zero will receive no MachineSets, but
creating MachineSets later on is something we want to be easy anyway,
so I don't see a need to require the installer to inject a template
MachineSet into the cluster.

pkg/asset/machines/worker.go

@@ -128,12 +128,15 @@ func (w *Worker) Generate(dependencies asset.Parents) error {
  mpool.InstanceType = awsDefaultWorkerMachineType(installconfig)
  mpool.Set(ic.Platform.AWS.DefaultMachinePlatform)
  mpool.Set(pool.Platform.AWS)
- if len(mpool.Zones) == 0 {
+ if pool.Replicas != nil && *pool.Replicas > 0 && len(mpool.Zones) == 0 {
  azs, err := aws.AvailabilityZones(ic.Platform.AWS.Region)
  if err != nil {
  return errors.Wrap(err, "failed to fetch availability zones")
  }
  mpool.Zones = azs
+ if int(*pool.Replicas) < len(mpool.Zones) {
+ mpool.Zones = azs[:*pool.Replicas]
+ }
  }
  pool.Platform.AWS = &mpool
  sets, err := aws.MachineSets(clusterID.InfraID, ic, &pool, string(*rhcosImage), "worker", "worker-user-data")