Getting started with k8s on Docker for Mac / Windows
I'm using zsh, so all I need to do is add kubectl to plugins section
So now we are ready to go with k8s!
Let's run nginx:
➜ ~ kubectl run --image nginx:alpine web
deployment.apps "web" createdCheck available deployments:
➜ ~ kubectl get deployments
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
web 1 1 1 1 2mReplication set:
➜ ~ kubectl get replicaset
NAME DESIRED CURRENT READY AGE
web-bbcdd5f4 1 1 1 4mAnd finally get pods where created:
➜ ~ kubectl get pod
NAME READY STATUS RESTARTS AGE
web-bbcdd5f4-zqq5x 1/1 Running 0 5mLet's get more information about our nginx web deployment
➜ ~ kubectl describe deployment web
Name: web
Namespace: default
CreationTimestamp: Sun, 04 Nov 2018 15:14:38 +0200
Labels: run=web
Annotations: deployment.kubernetes.io/revision=1
Selector: run=web
Replicas: 1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 1 max unavailable, 1 max surge
Pod Template:
Labels: run=web
Containers:
web:
Image: nginx:alpine
Port: <none>
Host Port: <none>
Environment: <none>
Mounts: <none>
Volumes: <none>
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet: web-bbcdd5f4 (1/1 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 7m deployment-controller Scaled up replica set web-bbcdd5f4 to 1Let's test our nginx web app. We can access web deployment via it's pod, so let's do that!
First of all we need to get nginx web pod name
➜ ~ kubectl get pod
NAME READY STATUS RESTARTS AGE
web-bbcdd5f4-zqq5x 1/1 Running 0 9mNow we can forward nginx pod port exposed by default (80) to for example local port 8080 just like so:
➜ ~ kubectl port-forward web-bbcdd5f4-zqq5x 8080:80
Forwarding from 127.0.0.1:8080 -> 80
Forwarding from [::1]:8080 -> 80Now, let's test if it's working...
With that we make sure that nginx web container is running and handling traffic
➜ ~ kubectl expose deployment web --port 80 --type NodePort
service "web" exposedLet's get services we currently have:
➜ ~ kubectl get service
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 1h
web NodePort 10.110.125.231 <none> 80:30906/TCP 50sAs you ca nsee port 80 of nginx web deploymemnt locally exposed on port 30906. Let's test this time if port 30906 is actually working:
➜ ~ http :30906
HTTP/1.1 200 OK
Accept-Ranges: bytes
Connection: keep-alive
Content-Length: 612
Content-Type: text/html
Date: Sun, 04 Nov 2018 14:18:30 GMT
ETag: "5bb3c541-264"
Last-Modified: Tue, 02 Oct 2018 19:21:37 GMT
Server: nginx/1.15.5
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>and it does.
Now I would like to use reverse-engineering principle to get current kubernetes service definition into yaml file:
➜ ~ kubectl get service web -o yaml > /tmp/web-service.yamlNot let's correct our service definition like so:
➜ ~ cat /tmp/web-service.yaml
apiVersion: v1
kind: Service
metadata:
labels:
run: web
name: web
namespace: default
selfLink: /api/v1/namespaces/default/services/web
spec:
externalTrafficPolicy: Cluster
ports:
- nodePort: 30000
port: 80
protocol: TCP
targetPort: 80
selector:
run: web
sessionAffinity: None
type: NodePort
status:
loadBalancer:
ingress:
- hostname: localhostNow we can re-create web service:
➜ ~ kubectl apply -f /tmp/web-service.yaml
Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply
service "web" configuredVerify service was updated as expected:
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 1h
web NodePort 10.104.17.108 <none> 80:30000/TCP 10mNow we can use out app on http://localhost:30000
If you will try set in /tmp/web-service.yaml file: spec.ports[0].nodePort = 8080, or any other < 30000 value, during kubectl apply you will get an error like this:
➜ ~ kubectl apply -f /tmp/web-service.yaml
Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply
The Service "web" is invalid: spec.ports[0].nodePort: Invalid value: 8080: provided port is not in the valid range. The range of valid ports is 30000-32767TODO: Investigate how we can fix it...
Setup:
➜ kubectl apply -f /tmp/app.yaml
secret "postgres-password-secret" created
persistentvolumeclaim "db-pvc" created
deployment.apps "postgres" created
service "postgres-node-port-dev-svc" created
service "postgres-clister-ip-svc" created
deployment.apps "web" created
service "web-node-port-dev-svc" created
service "web-cluster-ip-svc" createdVerify:
➜ kubectl get -f /tmp/app.yaml
NAME TYPE DATA AGE
secret/postgres-password-secret Opaque 1 2m
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
persistentvolumeclaim/db-pvc Bound pvc-f6161902-e0a4-11e8-93d4-025000000001 1Gi RWO hostpath 2m
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
deployment.apps/postgres 1 1 1 1 2m
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/postgres-node-port-dev-svc NodePort 10.107.237.57 <none> 5432:32345/TCP 2m
service/postgres-clister-ip-svc ClusterIP 10.110.232.11 <none> 5432/TCP 2m
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
deployment.apps/web 2 2 2 2 2m
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/web-node-port-dev-svc NodePort 10.97.202.253 <none> 80:30000/TCP 2m
service/web-cluster-ip-svc ClusterIP 10.96.135.4 <none> 80/TCP 2m