Istio consumes _many_ different types of clients (at the time of writing, 7), as well as informers for each of these.
Additionally, we often need to convert to various different client forms for different libraries we integrate with.

`kube.Client` just bundles these all in one place, so we have a single object to pass around anywhere we need Kubernetes access.

  // +optional
  optional k8s.io.api.core.v1.ObjectReference related = 9;

  // note is a human-readable description of the status of this operation.
  // Maximal length of the note is 1kB, but libraries should be prepared to
  // handle values up to 64kB.
  // +optional
  optional string note = 10;

  // type is the type of this event (Normal, Warning), new types could be added in the future.

}

func getClientForResource(resname, ns string, factory cmdutil.Factory) (*corev1client.CoreV1Client, string, string, string, error) {
	// Pod is referred to using something like "deployment/httpbin".  Use the kubectl
	// libraries to look up the resource name, find the pods it selects, and return
	// one of those pods.
	builder := factory.NewBuilder().
		WithScheme(kubelib.IstioScheme, kubelib.IstioScheme.PrioritizedVersionsAllGroups()...).

# I tried to make this dependent on what I thought was the appropriate
# lock file, but it caused the rule for that file to get run (which
# seems to be about obtaining a new version of the 3rd party libraries).
$(TARGET_OUT)/istio_is_init: bin/init.sh istio.deps | $(TARGET_OUT)
	@# Add a retry, as occasionally we see transient connection failures to GCS
	@# Like `curl: (56) OpenSSL SSL_read: SSL_ERROR_SYSCALL, errno 104`

# The following section is used as base image if BASE_DISTRIBUTION=distroless
# This image is a custom built debian11 distroless image with multiarchitecture support.
# It is built on the base distroless image, with iptables binary and libraries added
# The source can be found at https://github.com/istio/distroless/tree/iptables
# This version is from commit 86c4972a9f5f245cfb382c8e1e95f176d968c882.

  // +optional
  optional k8s.io.api.core.v1.ObjectReference related = 9;

  // note is a human-readable description of the status of this operation.
  // Maximal length of the note is 1kB, but libraries should be prepared to
  // handle values up to 64kB.
  // +optional
  optional string note = 10;

  // type is the type of this event (Normal, Warning), new types could be added in the future.

### Writing controllers

Istio provides a few helper libraries to get started writing a controller. While these libraries help, there are still a lot of subtleties in correctly writing (and testing!) a controller properly.