Default k8s services domains are hardcoded in trigger, can`t specify it in config

[mgolovatiy-atconsulting-ru]

Is this a BUG REPORT or FEATURE REQUEST?:
bug

What happened:
After kafka message put into queue, kafka-trigger-controller pod shows error in logs

time="2020-02-20T16:23:07Z" level=error msg="Failed to send message to function: Post http://nodejs-kafka-consumer-sample.<test_namespace_here>.svc.cluster.local:8080: dial tcp: lookup nodejs-kafka-consumer-sample.<test_namespace_here>.svc.cluster.local on 10.233.0.3:53: no such host"

What you expected to happen:
Trigger send message to function pod nodejs-kafka-consumer-sample, can see logged event in its logs.

May be this domain should be got from configMap (kubeless-config?).

How to reproduce it (as minimally and precisely as possible):

• K8s server, one namespace with all demanded deployments, statefulSets, etc. Have configured kafka+zoo+kafkaHq.
• Deploy function, trigger:

kubeless function deploy nodejs-kafka-consumer-sample --runtime nodejs12 \
	--dependencies kafkaConsumer_dependency.json \
	--handler kafkaConsumer.consumeTagTopic 	 \
        --from-file kafkaConsumer.js
kubeless trigger kafka create nodejs-kafka-consumer-sample --function-selector created-by=kubeless,function=nodejs-kafka-consumer-sample --trigger-topic nodejs-kafka-consumer-sample-in

• using kafkaHq add message (topic created by this new function)
• check trigger pod logs

Anything else we need to know?:
kubelet run with --cluster-domain=k8s.test option
Sources have hardcoded literal with domain:
event_sender.go: 57

 fmt.Sprintf("http://%s.%s.svc.cluster.local:%s", funcName, namespace, funcPort)

Seems to be bug.

Environment:

• Kubernetes version: 1.11.3
• Kubeless version: 1.0.5-dirty
• Cloud provider or physical cluster: physical
• Kafka statefull set + Zoo statefull set installed/configured before, publishing messages via kafka UI (kafkaHQ)
• Kafka, Zoo, Triggers, Functions, Kubeless, kubeless-config at one namespace on the test k8s server.
• HTTP trigger works well (js script in function).

[andresmgot]

Hi @mgolovatiy-atconsulting-ru,

Thanks for reporting the issue. You mention that the cluster domain has been changed in your case. What would be the correct URL for your function? (Rather than http://%s.%s.svc.cluster.local:%s)

[mgolovatiy-atconsulting-ru]

svc.cluster.local -> k8s.test that specified as cluster-domain param in kube.
So correct solution should be
fmt.Sprintf("http://%s.%s.%s:%s", funcName, namespace, kubeDomain, funcPort)
where kubeDomain should be configured in configMap or another place.

Or, may be, should query domain via k8s api, don`t know if it is possible. If i know go, i could make PR as soon as noticed this.

[andresmgot]

In theory the .svc is not part of the domain so http://%s.%s.svc.%s:%s", funcName, namespace, kubeDomain, funcPort) should work for you as well.

I see that parameter available in the kubelet configmap present in the kube-system namespace but it seems a bit difficult to retrieve. Probably it's better to configure it just as a flag for the kafka-trigger-controller deployment.

Marking this up for grabs since I don't have the bandwidth to work on this right now. Happy to help to anyone to want to give this a try.

[mgolovatiy-atconsulting-ru]

@andresmgot I suggest a solution without introducing an enviroment variable:

1. kubeless-> add getClusterDomain function (in utils.k8sutil) - shall it be usefull?
2. kafka-trigger -> add the same function in utils.k8sutil (is it another package?)

func getClusterDomain() string {
	apiSvc := "kubernetes.default.svc"

	clusterDomain := "cluster.local"

	cname, err := net.LookupCNAME(apiSvc)
	if err != nil {
		return clusterDomain
	}

	clusterDomain = strings.TrimPrefix(cname, apiSvc)
	clusterDomain = strings.TrimSuffix(clusterDomain, ".")

	return clusterDomain
}

Seems to be pretty simple.

3. kafka-trigger -> fix event_sender.GetHTTPReq :

   req, err := http.NewRequest(method, fmt.Sprintf("http://%s.%s.svc.%s:%s", funcName, namespace, getClusterDomain(), funcPort), strings.NewReader(body))

Don't have unix, so cant test well, even can't run makefile.

Need CR due to my zero go-expirence

[andresmgot]

Comments in the PR. I think it's easier to leave this code in kafka trigger for the moment (no need to move it kubeless core).

[mgolovatiy-atconsulting-ru]

Couldn`t find in which repo new image was put, wish to use it with my test enviroment. Can i use some snapshot or only must wait for stable version?

[andresmgot]

I have a working environment so I have built the image for you, you can use it as andresmgot/kafka-trigger-controller:mgolovatiy-atconsulting-ru and test it

[mgolovatiy-atconsulting-ru]

Thank u

[mgolovatiy-atconsulting-ru]

My solution doesn't work, have the same error. Don't understand why net.LookupCNAME("kubernetes.default.svc") returns wrong domain.

This question seems to be raised long before: vmware-archive/kubeless#832
I think it is a good idea to specify domain on creating function or trigger. May be it should be reopened?

[andresmgot]

Sorry to hear that.

I think it is a good idea to specify domain on creating function or trigger. May be it should be reopened?

Well, it's not related to a specific function or trigger but to a cluster. I think this should be a flag for the trigger controller just as it was started in vmware-archive/kubeless#857.

I think you are close with your implementation, you just need to use a command flag instead of trying to auto-resolve the domain.