Connect a Frontend to a Backend Using Services

[assafseif]

Why i cant server frontend deployment

i got

2024/04/22 11:20:02 [emerg] 1#1: host not found in upstream "hello" in /etc/nginx/conf.d/frontend.conf:2
nginx: [emerg] host not found in upstream "hello" in /etc/nginx/conf.d/frontend.conf:2

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[tamilselvan1102]

/kind support

[assafseif]

/kind support

what should i do?

[tamilselvan1102]

you can deploy front-end/back-end app in k8s containers. Please check your app and its configurations

[assafseif]

thats what i did exactly like this
https://kubernetes.io/docs/tasks/access-application-cluster/connecting-frontend-backend/

and i got this

2024/04/22 11:20:02 [emerg] 1#1: host not found in upstream "hello" in /etc/nginx/conf.d/frontend.conf:2
nginx: [emerg] host not found in upstream "hello" in /etc/nginx/conf.d/frontend.conf:2

[tamilselvan1102]

which step did you get the error

[assafseif]

i got crashloopbackoff when deploying frontend
what i showed you is the log of frontend deployment pod

[tamilselvan1102]

crashloopbackoff may occur because of Resource Overload or Insufficient Memory, Misconfigurations. ...
please investigate your pod logs and resolve the issue

[tamilselvan1102]

@assafseif
GitHub is not the right place for support requests.

If you're looking for help, check Server Fault.

You can also post your question on the Kubernetes Slack or the Discuss Kubernetes forum.

[sftim]

If you'd like to explain more about how to replicate the issue, @assafseif, we may be able to fix the documentation (we can't advise on specifics for your cluster).

/remove-kind support
/triage needs-information
/language en

[assafseif]

If you'd like to explain more about how to replicate the issue, @assafseif, we may be able to fix the documentation (we can't advise on specifics for your cluster).

/remove-kind support /triage needs-information /language en
hello ,

What i tried to do is deploying frontend,
Check this one
https://kubernetes.io/docs/tasks/access-application-cluster/connecting-frontend-backend/#creating-the-frontend

kubectl apply -f https://k8s.io/examples/service/access/frontend-deployment.yaml
kubectl apply -f https://k8s.io/examples/service/access/frontend-service.yaml

crashloopbackoff occured inbside frontend-deployment pods,
when describing i got
host not found in upstream "hello" in /etc/nginx/conf.d/frontend.conf:2
nginx: [emerg] host not found in upstream "hello" in /etc/nginx/conf.d/frontend.conf:2

all files applied are from kubernetes docs

Regards

[stmcginnis]

OK, looking in to this a little closer, it looks like there is an issue with the gcr.io/google-samples/hello-frontend:1.0 image used by frontend-deploy.yaml.

To clarify some of the description here, this is following the Connect a Frontend to a Backend Using Services tutorial. One of the steps there is to apply a manifest to create a new frontend deployment named frontend.

That deployment defines 1 replica, with the pod using the gcr.io/google-samples/hello-frontend:1.0 image.

The pod gets created, but ends up in a CrashLoopBackoff state. Describe the pod shows there is a problem in the events:

Events:
  Type     Reason     Age                From               Message
  ----     ------     ----               ----               -------
  Normal   Scheduled  31s                default-scheduler  Successfully assigned default/frontend-758994b889-tfd68 to kind-control-plane
  Normal   Pulling    31s                kubelet            Pulling image "gcr.io/google-samples/hello-frontend:1.0"
  Normal   Pulled     28s                kubelet            Successfully pulled image "gcr.io/google-samples/hello-frontend:1.0" in 3.247s (3.247s including waiting)
  Normal   Created    10s (x3 over 28s)  kubelet            Created container nginx
  Normal   Started    10s (x3 over 28s)  kubelet            Started container nginx
  Normal   Pulled     10s (x2 over 27s)  kubelet            Container image "gcr.io/google-samples/hello-frontend:1.0" already present on machine
  Warning  BackOff    10s (x3 over 26s)  kubelet            Back-off restarting failed container nginx in pod frontend-758994b889-tfd68_default(eae930af-0164-48a7-bc59-6022b8db560f)

In this case the pod name is frontend-758994b889-tfd68_default. If I get the logs we see the error mentioned above:

$ kubectl logs pod/frontend-758994b889-tfd68_default
2024/04/23 13:53:15 [emerg] 1#1: host not found in upstream "hello" in /etc/nginx/conf.d/frontend.conf:2
nginx: [emerg] host not found in upstream "hello" in /etc/nginx/conf.d/frontend.conf:2

This is after skipping the first half of the tutorial where the backend is created. Since this frontend proxies to the backend service, and the backend service defines a service named "hello", it appears the frontend will try to start, not find what it needs from the backend, and fail.

To check that, I then went back to the beginning and followed all steps up to the frontend deployment. After creating the backend as documented, the frontend was able to start and everything appears happy:

k get all
NAME                            READY   STATUS    RESTARTS        AGE
pod/backend-7f5b7998b9-2fcl2    1/1     Running   0               87s
pod/backend-7f5b7998b9-rv4mz    1/1     Running   0               87s
pod/backend-7f5b7998b9-snn5c    1/1     Running   0               87s
pod/frontend-758994b889-tfd68   1/1     Running   7 (5m21s ago)   11m

NAME                 TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
service/hello        ClusterIP   10.96.88.204   <none>        80/TCP    56s
service/kubernetes   ClusterIP   10.96.0.1      <none>        443/TCP   44m

NAME                       READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/backend    3/3     3            3           87s
deployment.apps/frontend   1/1     1            1           11m

NAME                                  DESIRED   CURRENT   READY   AGE
replicaset.apps/backend-7f5b7998b9    3         3         3       87s
replicaset.apps/frontend-758994b889   1         1         1       11m

[tienhuynh17]

Hmm, I face the same issue. And I have followed all steps of the tutorial.