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Kubernetes Guide

Naming

Name Definition
K8s Kubernetes
Pod Pods are the smallest deployable units of computing that can be created and managed in Kubernetes.
Service An abstract way to expose an application running on a set of Pods as a network service.
Deployments A Deployment provides declarative updates for Pods and ReplicaSets.
ReplicaSet A ReplicaSet's purpose is to maintain a stable set of replica Pods running at any given time. As such, it is often used to guarantee the availability of a specified number of identical Pods.
DaemonSet A DaemonSet ensures that all (or some) Nodes run a copy of a Pod.
Ingress An API object that manages external access to the services in a cluster, typically HTTP.

1. Create Docker Image

Kubernetes will always look at an Image Registry. So, for this example I will upload to my Docker Hub (https://hub.docker.com/u/vepo). If you want to rebuilt it, replace "vepo" by your Docker Hub user.

docker build backend/ -t backend
docker tag backend vepo/backend:1.0.0
docker push vepo/backend:1.0.0

docker build frontend/ -t frontend
docker tag frontend vepo/frontend:1.0.0
docker push vepo/frontend:1.0.0

2. Deploy PODs

The script k8s/pods/all.yaml contains a definition to both Containers as POD.

$ kubectl apply -f k8s/pods/all.yaml
pod/backend created
pod/frontend created

We can query it by filtering the label example=k8s:

$ kubectl get pods -l example=k8s
NAME       READY   STATUS    RESTARTS   AGE
backend    1/1     Running   0          2m21s
frontend   1/1     Running   0          2m21s

Problem!

PODs cannot be accessed externally! We need services

Expose Pod as a Service:

$ kubectl expose pod frontend --type NodePort --name frontend-svc
service/frontend-svc exposed

Describe the service:

$ kubectl describe svc frontend-svc
Name:                     frontend-svc
Namespace:                default
Labels:                   app=k8s-tutorial
                          example=k8s
                          role=frontend
                          version=v1
Annotations:              <none>
Selector:                 app=k8s-tutorial,example=k8s,role=frontend,version=v1
Type:                     NodePort
IP:                       10.102.163.164
LoadBalancer Ingress:     localhost
Port:                     <unset>  8080/TCP
TargetPort:               8080/TCP
NodePort:                 <unset>  30066/TCP
Endpoints:                10.1.0.34:8080
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

We can access the service by http://<Node IP>:<NodePort>. Now just access through localhost:30066.

Cleanup

kubectl delete svc frontend-svc
kubectl delete -f k8s/pods/all.yaml

3. Deploy Services

To deploy all using PODs and Services:

kubectl apply -f k8s/services/all.yaml

Then you have to inspect the service to find which port use to access it.

kubectl describe svc frontend-svc
``

## Cleanup

```bash
kubectl delete -f k8s/services/all.yaml

4. Deploy Deployments

To deploy all using PODs, Services and Deployments

kubectl apply -f k8s/deployments/all.yaml

Then you have to inspect the service to find which port use to access it.

kubectl describe svc frontend-svc

To check all running pods:

kubectl get pods -l app=k8s-tutorial

Cleanup

kubectl delete -f k8s/deployments/all.yaml

Helm

Configure the repo:

helm repo add jaegertracing https://jaegertracing.github.io/helm-charts

Search for versions:

helm search repo jaeger

Install:

helm install tracing  jaegertracing/jaeger --version 0.32.0

Problem! Jaeger is configure to be exposed as Cluster IP!

Just upgrade using the values

helm upgrade tracing jaegertracing/jaeger  --version 0.25 --values helm/jaeger-node-port.yaml

Cleanup

helm delete tracing