Exploring Your App

In this scenario you will learn how to troubleshoot Kubernetes applications using the kubectl get, describe, logs and exec commands.

Check application configuration

kubectl get pods

NAME                                   READY     STATUS    RESTARTS   AGE
kubernetes-bootcamp-5c69669756-vdwgm   1/1       Running   0          11m

kubectl describe pods

Name:           kubernetes-bootcamp-5c69669756-vdwgm
Namespace:      default
Node:           minikube/10.0.2.15
Start Time:     Sun, 10 Jun 2018 15:08:15 +0000
Labels:         pod-template-hash=1725225312
                run=kubernetes-bootcamp
Annotations:    <none>
Status:         Running
IP:             172.17.0.4
Controlled By:  ReplicaSet/kubernetes-bootcamp-5c69669756
Containers:
  kubernetes-bootcamp:
    Container ID:   docker://b3c882ba24392b8b1417e420ac45c351959098cacc82fe59a64dff9d6e3859d6
    Image:          gcr.io/google-samples/kubernetes-bootcamp:v1
    Image ID:       docker-pullable://gcr.io/google-samples/kubernetes-bootcamp@sha256:0d6b8ee63bb57c5f5b6156f446b3bc3b3c143d233037f3a2f00e279c8fcc64af
    Port:           8080/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Sun, 10 Jun 2018 15:08:48 +0000
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-x5428 (ro)
Conditions:
  Type           Status
  Initialized    True
  Ready          True
  PodScheduled   True
Volumes:
  default-token-x5428:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-x5428
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason                 Age   From               Message
  ----    ------                 ----  ----               -------
  Normal  Scheduled              12m   default-scheduler  Successfully assigned kubernetes-bootcamp-5c69669756-vdwgm to minikube
  Normal  SuccessfulMountVolume  12m   kubelet, minikube  MountVolume.SetUp succeeded for volume "default-token-x5428"
  Normal  Pulling                12m   kubelet, minikube  pulling image "gcr.io/google-samples/kubernetes-bootcamp:v1"
  Normal  Pulled                 11m   kubelet, minikube  Successfully pulled image "gcr.io/google-samples/kubernetes-bootcamp:v1"
  Normal  Created                11m   kubelet, minikube  Created container
  Normal  Started                11m   kubelet, minikube  Started container

Show the app in the terminal

We need to get the Pod name, and we'll store in the environment variable POD_NAME

export POD_NAME=$(kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')

echo Name of the Pod: $POD_NAME
Name of the Pod: kubernetes-bootcamp-5c69669756-vdwgm

Now we can make an HTTP request to the application running in that pod

curl http://localhost:8001/api/v1/namespaces/default/pods/$POD_NAME/proxy/

Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-5c69669756-vdwgm | v=1

The url is the route to the API of the Pod.

View the container logs

kubectl logs $POD_NAME

Kubernetes Bootcamp App Started At: 2018-06-10T15:08:48.691Z | Running On:  kubernetes-bootcamp-5c69669756-vdwgm

Running On: kubernetes-bootcamp-5c69669756-vdwgm | Total Requests: 1 | App Uptime: 385.809 seconds | Log Time: 2018-06-10T15:15:14.500Z
Running On: kubernetes-bootcamp-5c69669756-vdwgm | Total Requests: 2 | App Uptime: 811.04 seconds | Log Time: 2018-06-10T15:22:19.731Z
Running On: kubernetes-bootcamp-5c69669756-vdwgm | Total Requests: 3 | App Uptime: 846.227 seconds | Log Time: 2018-06-10T15:22:54.918Z

Executing command on the container

List the environment variables

kubectl exec $POD_NAME env

PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=kubernetes-bootcamp-5c69669756-vdwgm
KUBERNETES_SERVICE_PORT=443
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_PORT=tcp://10.96.0.1:443
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_PORT=443
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
KUBERNETES_SERVICE_HOST=10.96.0.1
NPM_CONFIG_LOGLEVEL=info
NODE_VERSION=6.3.1
HOME=/root

Start a bash session in the Pod’s container

kubectl exec -ti $POD_NAME bash

root@kubernetes-bootcamp-5c69669756-vdwgm:/#

We have now an open console on the container where we run our NodeJS application. The source code of the app is in the server.js file

cat server.js

var http = require('http');
var requests=0;
var podname= process.env.HOSTNAME;
var startTime;
var host;
var handleRequest = function(request, response) {
  response.setHeader('Content-Type', 'text/plain');
  response.writeHead(200);
  response.write("Hello Kubernetes bootcamp! | Running on: ");
  response.write(host);
  response.end(" | v=1\n");
  console.log("Running On:" ,host, "| Total Requests:", ++requests,"| App Uptime:", (new Date() - startTime)/1000 , "seconds", "| Log Time:",new Date());
}
var www = http.createServer(handleRequest);
www.listen(8080,function () {
    startTime = new Date();;
    host = process.env.HOSTNAME;
    console.log ("Kubernetes Bootcamp App Started At:",startTime, "| Running On: " ,host, "\n" );
});

curl localhost:8080

Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-5c69669756-vdwgm | v=1

We used localhost because we executed the command inside the NodeJS container

root@kubernetes-bootcamp-5c69669756-vdwgm:/# exit
exit
hadoop@salt:~$