• Troubleshoot Kubernetes service not being resolved

    2 min read

    unresolving kubernetes service DNS

    When you create a Kubernetes Service, pods from within the same namespace should be able to resolve it's IP by name. For example, if we create a service named ampa-votacions; any pod from the same namespace should be able to resolve it's IP. But sometimes it can't be resolved:

    $ kubectl exec -it ampa-install-ws7cw -- sh
/ $ nslookup ampa-votacions
Server:   172.20.0.10
Address:  172.20.0.10:53

** server can't find ampa-votacions.us-west-2.compute.internal: NXDOMAIN

** server can't find ampa-votacions.ampa.svc.cluster.local: NXDOMAIN

** server can't find ampa-votacions.svc.cluster.local: NXDOMAIN

** server can't find ampa-votacions.ampa.svc.cluster.local: NXDOMAIN

** server can't find ampa-votacions.cluster.local: NXDOMAIN

** server can't find ampa-votacions.svc.cluster.local: NXDOMAIN

** server can't find ampa-votacions.cluster.local: NXDOMAIN

** server can't find ampa-votacions.us-west-2.compute.internal: NXDOMAIN

    19/04/2021

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  • kubernetes services: NodePort type usage

    2 min read

    kubernetes service NodePort

    To be able to expose a given Service externally, we can use NodePort as a quick-and-dirty way of achieving it. NodePort Services use a port on each Node to expose the Service outside of the cluster network

    02/03/2021

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  • Error syncing load balancer: failed to ensure load balancer: could not find any suitable subnets for creating the ELB

    2 min read

    If we try to create a LoadBalancer on an AWS EKS cluster without any public subnet it will get stuck on the pending state and we won't get any external IP/DNS name for it. By using kubectl describe we will be able to get the actual error:

    $ kubectl get svc -n pet2cattle
NAME      TYPE           CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
demo-lb   LoadBalancer   172.20.235.213   <pending>     80:30525/TCP   7d
$ kubectl describe svc demo-lb -n pet2cattle 
Name:                     demo-lb
Namespace:                pet2cattle
Labels:                   <none>
Annotations:              <none>
Selector:                 run=demo-lb
Type:                     LoadBalancer
IP Families:              <none>
IP:                       172.20.166.181
IPs:                      <none>
Port:                     <unset>  80/TCP
TargetPort:               80/TCP
NodePort:                 <unset>  30088/TCP
Endpoints:                10.236.124.69:80,10.236.126.253:80
Session Affinity:         None
External Traffic Policy:  Cluster
Events:
  Type     Reason                  Age                From                Message
  ----     ------                  ----               ----                -------
  Normal   EnsuringLoadBalancer    12s (x3 over 27s)  service-controller  Ensuring load balancer
  Warning  SyncLoadBalancerFailed  12s (x3 over 27s)  service-controller  Error syncing load balancer: failed to ensure load balancer: could not find any suitable subnets for creating the ELB

    17/02/2021

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  • kubernetes services: externalName

    2 min read

    externalName service kubernetes

    One of kind of Service objects on kubernetes is extenalName. It creates a CNAME DNS entry to point to an external DNS service. For exemple:

    kind: Service
apiVersion: v1
metadata:
  name: ensvc
spec:
  type: ExternalName
  externalName: pet2cattle.com

    29/01/2021

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From pet to cattle
Treat your kubernetes clusters like cattle, not pets