Introduce support for Waiting for given cluster conditions

[vladimirvivien]

As a test writer of components running on Kubernetes, it would be extremely useful to have the capability to wait for one or more cluster conditions before proceeding in the test.

A framework for Waiting

A new package klient/wait could be the starting point for an API to express conditions for waiting by leveraging the wait package in API machinery "k8s.io/apimachinery/pkg/util/wait"):

package wait

func For(cond func() (bool, error)){...}

So, a test writer may have condition as follows:

func TestSomething(t *testing.T){
    wait.For(t, func() (bool, error) {
        var ns coreV1.Namespace
        cfg.client.List(ns)
        ...
    )}
}

Pre-defined conditions

The framework could have a collection of pre-defined conditions that can be used by test writers:

func TestSomething(t *testing.T) {
   var pod coreV1.Pod
   wait.For(PodReadyCondition(pod))
}

[harshanarayana]

@vladimirvivien Would you mind assigning this issue to me so that I can take a stab at this if not already being looked at by someone else. ?

[vladimirvivien]

@harshanarayana I missed that ping. Sorry.

[harshanarayana]

No worries @vladimirvivien Let me open a PR with some prototype for a feedback.

[harshanarayana]

@vladimirvivien I have opened a draft PR for the same. Hope the changes in there matches with what you had in mind for this behavior.