Kubernetes

Kubernetes

Samples #

Application #

cat > app.js <<EOF
const http = require('http');
const os = require("os");
const hostname = '0.0.0.0';
const port = 80;
const server = http.createServer((req, res) => {
    console.log('Request: ' + req.url);
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    res.end('Hello World from ' + os.hostname() + '\n');
});
server.listen(port, hostname, () => {
    console.log('Server running at http://%s:%s/', hostname, port);
});
process.on('SIGINT', function() {
    console.log('Caught interrupt signal and will exit');
    process.exit();
});
EOF

Dockerfile #

cat > Dockerfile <<EOF
# Use an official Node runtime as the parent image
FROM node:6

# Set the working directory in the container to /app
WORKDIR /app

# Copy the current directory contents into the container at /app
ADD . /app

# Make the container's port 80 available to the outside world
EXPOSE 80

# Run app.js using node when the container launches
CMD ["node", "app.js"]
EOF

Building image #

  • docker build -t gcr.io/PROJECT_ID/hello-node:v1 . -
  • gcloud docker -- push gcr.io/PROJECT_ID/hello-node:v1

Deployment #

  • kubectl run hello-node --image=gcr.io/PROJECT_ID/hello-node:v1 --port=8080 - create and run deployment
  • kubectl get deployments - list all deployments
  • kubectl edit deployment hello-node - after introduce change in the image and release given deployment can be updated with new container image version and apply it

Status #

  • kubectl get pods - list all running pods
  • kubectl get pods -l "key1=value1,key2=value2" - list all pods with multiple labels
  • kubectl get pods <pod-name> --show-labels - list pods with labels
  • kubectl label pods <pod-name> 'key=value' - set labels to the pod
  • kubectl cluster-info
  • kubectl config view
  • kubectl get events
  • kubectl logs <pod-name>
  • kubectl describe pods <pod-name>

Interacting with pods #

  • kubectl port-forward monolith 8080:80 - forwarding port from pod 80 to local 8080
  • kubectl exec <pod-name> --stdin --tty /bin/sh - “enter” container (ssh replacement)
  • kubectl exec <pod-name> --stdin --tty -c <container-name> /bin/sh - “enter” container (ssh replacement)

Services #

Types:

  • ClusterIP (internal) - the default type means that this Service is only visible inside of the cluster
  • NodePort - gives each node in the cluster an externally accessible IP
  • LoadBalancer - adds a load balancer from the cloud provider which forwards traffic from the service to Nodes within it.

Commands:

  • kubectl get services - list all services
  • kubectl expose deployment <deployent-name> --type="LoadBalancer" –port=8080 - create service of type LoadBalancer

Scaling #

  • kubectl scale deployment <deployent-name> --replicas=4 - manually scale pods to the count of total = 4

Rolling update #

  • kubectl edit deployment <deployent-name> - vim deployment descriptor
  • kubectl rollout history deployment/<deployent-name> - rolling history
  • kubectl rollout pause deployment/<deployent-name> - rolling update pause
  • kubectl rollout status deployment/<deployent-name> - rolling status
  • kubectl get pods -o jsonpath --template='{range .items[*]}{.metadata.name}{"\t"}{"\t"}{.spec.containers[0].image}{"\n"}{end}' - erify rolling status on pods directly
  • kubectl rollout undo deployment/hello - uno latest deployment
  • canary release: https://google.qwiklabs.com/focuses/7013
  • blue green deployment: https://google.qwiklabs.com/focuses/7013

Web console #

  • gcloud container clusters get-credentials hello-world \ --zone us-central1-f --project <PROJECT_ID> - configure kubectl command before usage
  • kubectl proxy --port 8081 and open /ui - proxy traffic to the kubernetes console

Create object #

  • kubectl create -f <object>.yaml - create object from file

Debbuging #

  • kubectl -n kube-system get cm kubeadm-config -oyaml
  • kubectl get pods --all-namespaces
  • kubectl -n <namespace-name> describe pod <pod name>
  • kubectl -n mortgages-dev2 logs -p <pod name>

Istio #

  • Traffic Management
  • Authentication between services
  • Authorization between services
  • Secure communication between services
  • Observability:
  • tracing
  • service discovery
  • load balancing
  • logging
  • monitoring
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