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10-Practice-Test-Troubleshoot-Network.md

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Solution Troubleshoot Network

Lets have a look at the Practice Test of the Troubleshoot Network

  1. Troubleshooting Test 1

    We are asked to ensure all the components are working, so first let's examine the cluster to see what state it is in.

    How many nodes, and their status?

    kubectl get nodes

    Seems OK...

    Next, the pods

    kubectl get pods -A

    Now we see that the webapp and mysql pods are stuck at ContainerCreating. We need to describe the pods and check the errors.

    You will note that they are complaining about network: unable to allocate IP address, so clearly we have a networking issue.

    When you did the get pods above, did you see any evidence of network support containers, like flannel or weave?

    No - so we need to install networking support.

    Let's install Weave

    kubectl apply -f https://github.com/weaveworks/weave/releases/download/v2.8.1/weave-daemonset-k8s.yaml

    Now wait for a minute or so for it to initialize, then check the application pods

    kubectl get pods -n triton
  2. Troubleshooting Test 2

    Once again let's examine the cluster to see what state it is in.

    How many nodes, and their status?

    kubectl get nodes

    Seems OK...

    Next, the pods

    kubectl get pods -A

    The kube-proxy pod is not running. It is actually crash-looping which means it tries to start, then fails. As a result the rules needed to allow connectivity to the services have not been created. First place to look when diagnosing CrashLoopBackoff is the pod logs.

    1. Check the logs of the kube-proxy pod

      kubectl -n kube-system logs <name_of_the_kube_proxy_pod>

      We see that it cannot find a configuration file.

      Now try looking for the configuration in case it has a different name

      ls -l /var/lib/kube-proxy

      The directory is not found!

    2. Inspect the pod template spec in the kube-proxy daemonset.

      kubectl get ds -n kube-system kube-proxy -o yaml | less

      Scroll around and check volumes and volume mounts. Notice that a config map is mounted at the path /var/lib/kube-proxy within the pod.

    3. Inspect the config map

      kubectl describe cm -n kube-system kube-proxy

      Here we see that the files mounted by the config map are config.conf and kubeconfig.conf, but not configuration.conf.

      These two files are

      • config.conf - This is the actual configuration that kube-proxy needs to load. This file refers to kubeconfig.conf
      • kubeconfig.conf - This is simply a a kubeconfig file, same as you will find on the lab terminal in ~/.kube/config. It is the credentials and address for kube-proxy to talk to the api server.

    4. Fix the command line arguments to kube-proxy

      kubectl edit ds -n kube-system kube-proxy

      Set the correct filename

      --config=/var/lib/kube-proxy/config.conf

      Finally, confirm it is running.

      kubectl get pods -n kube-system