Handle error while registering/deregistering target during load balancer update calls

[jaydeokar]

What type of PR is this?
/kind bug

What this PR does / why we need it:
If the RegisterInstancesWithLoadBalancer fails for any reason during an LoadBalancer Update call, we do not throw the error and return nil. So we will never know if the target group registration passes or fails

For testing -
I tried to mock the ELB API as I wasn't able to hit the throttling every time.

I introduced a 50% chance of ELB API failing to register the target using Mocked return message

		val := rand.Int()
		if val%2 != 0 {
			klog.V(1).Infof("Not using Mocked call %s", loadBalancerName)
			_, err = c.elb.RegisterInstancesWithLoadBalancer(registerRequest)
		} else {
			klog.V(1).Infof("Using Mocked call %s", loadBalancerName)
			err = fmt.Errorf("mocked throttled call")
		}

		if err != nil {
			return err
		}
		klog.V(1).Infof("Instances added to load-balancer %s", loadBalancerName)

The events on the service

Warning  UnAvailableLoadBalancer   6m31s                 service-controller  There are no available nodes for LoadBalancer
  Warning  UpdateLoadBalancerFailed  2m34s                 service-controller  Error updating load balancer with new hosts [i-035ae0c5cd612d191 i-05560870005eef14b i-0661ad74a5ae13914 i-0a48dd4251b3e24d3] [node names limited, total number of nodes: 4], error: mocked throttled call
  Normal   UpdatedLoadBalancer       2m6s (x6 over 6m58s)  service-controller  Updated load balancer with new hosts
  Warning  UpdateLoadBalancerFailed  53s                   service-controller  Error updating load balancer with new hosts [i-00153b6992defc5d0 i-035ae0c5cd612d191 i-05560870005eef14b i-0661ad74a5ae13914 i-0a48dd4251b3e24d3 i-0cc2ee458bb7db682] [node names limited, total number of nodes: 6], error: mocked throttled call
  Warning  SyncLoadBalancerFailed    28s (x6 over 2m30s)   service-controller  Error syncing load balancer: failed to ensure load balancer: mocked throttled call
  Normal   EnsuringLoadBalancer      8s (x9 over 13m)      service-controller  Ensuring load balancer
  Normal   EnsuredLoadBalancer       8s (x3 over 13m)      service-controller  Ensured load balancer

This shows that the controller retries and reconciles again in case of failures.

The logs in the controller shows the new warn message that was added

W0729 21:20:19.689788       1 aws.go:3016] Error registering/deregistering instances with the load balancer: "mocked throttled call"
I0729 21:20:19.747638       1 event.go:389] "Event occurred" object="ui/ui-nlb-11" fieldPath="" kind="Service" apiVersion="v1" type="Warning" reason="UpdateLoadBalancerFailed" message="Error updating load balancer with new hosts [i-00153b6992defc5d0 i-035ae0c5cd612d191 i-05560870005eef14b i-0661ad74a5ae13914 i-0a48dd4251b3e24d3 i-0cc2ee458bb7db682] [node names limited, total number of nodes: 6], error: mocked throttled call"

Which issue(s) this PR fixes:
N/A

Fixes #

Special notes for your reviewer:
N.A

Does this PR introduce a user-facing change?:
N/A

Fixes an bug with UpdateLoadBalancer call where any failure in RegisterInstances API to ELB is always returned as success

[k8s-ci-robot]

This issue is currently awaiting triage.

If cloud-provider-aws contributors determine this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[k8s-ci-robot]

Welcome @jaydeokar!

It looks like this is your first PR to kubernetes/cloud-provider-aws 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes/cloud-provider-aws has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[k8s-ci-robot]

Hi @jaydeokar. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[M00nF1sh]

/ok-to-test

[M00nF1sh]

/approve
/lgtm

[cartermckinnon]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cartermckinnon, M00nF1sh

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [cartermckinnon]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[jayanthvn]

/lgtm

[k8s-ci-robot]

@jayanthvn: changing LGTM is restricted to collaborators

In response to this:

/lgtm

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[kmala]

/lgtm