## Writing Controllers

The `controllers` package offers a variety of helpers for writing controllers.
These operate in a similar manner as [`controller-runtime`](https://github.com/kubernetes-sigs/controller-runtime) but are *far* smaller and less abstract.

With a few exceptions, Istio controllers typically are split in two phases: construction and running.

		switch {
		case !ok:
			// Cgroup did not contain a container ID.
			continue
		case containerID == "":
			// This is the first container ID found so far.
			podUID = candidatePodUID
			containerID = candidateContainerID
		case containerID != candidateContainerID:
			// More than one container ID found in the cgroups.