pkg

README

Kubernetes Golang Utilities for Verrazzano

This repository is a collection of general-purpose, Kubernetes-related Golang utilities used across Verrazzano.

How to use

To import within your project, run:

go get github.com/verrazzano/pkg

See below for specific examples of using the various packages.

Packages

./diff: Kubernetes Object Comparator

The utilities in this package are intended to be in used in the context of custom Kubernetes controllers, when comparing the live state of a Kubernetes object (fetched via API) against a desired state (constructed via code). The "live" object, fetched from Kubernetes, will auto-generate many fields that we won't or can't specify in the "desired" object that we construct. A common job of a Kubernetes controller is to compare a desired and live object, and Apply() changes if they are different. But we don't want these auto-generated fields to cause us to apply changes, otherwise we'd be doing so frequently. A standard Golang struct comparison will detect these as differences, and is therefore insufficient for our purposes here.

Our Diff() function simply performs a recursive struct comparison, but ignores any fields that were unspecified in the toObject (the desired object):

import (
        "github.com/verrazzano/pkg/diff"
)

Example: Detecting changes to a deployment object:

Fetch the live Kubernetes object:

cfg, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
if err != nil {
log.Fatal(err)
}
kubeClientSet, err := kubernetes.NewForConfig(cfg)
if err != nil {
log.Fatal(err)
}
kubeInformerFactory := kubeinformers.NewSharedInformerFactory(kubeClientSet, 30*time.Second)
deploymentInformer := kubeInformerFactory.Apps().V1().Deployments()
deploymentLister := deploymentInformer.Lister()
liveDeployment := deploymentsLister.Deployments("mynamespace").Get("mydeployment")

Construct your desired object:

desiredDeployment := createMyDeploymentObject()

Compare:

diffs := diff.Diff(liveDeployment, desiredDeployment)
if diffs != "" {
	fmt.Println("Diffs: " + diffs)
}