https://github.com/kubernetes/minikube#installation
Start
$ minikube start
Status
$ minikube status
$ source <(kubectl completion bash)Run a local registry (ignore this step if using DockerHub)
$ docker run -d -p 5000:5000 registryBuild Docker Image
$ docker build -t ramays/springldap .Retag to Push to Local Registry
$ docker tag ramays/springldap localhost:5000/dev/ramays/springldapPush to Local Registry
$ docker push localhost:5000/dev/ramays/springldapRun a single pod using the Kubernetes command line, inspect the Pod and then invoke the Spring Boot App
$ kubectl run springldap --image=localhost:5000/dev/ramays/springldap --port=9090 --generator=run-pod/v1
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
springldap 1/1 Running 0 107s
$ kubectl describe pod/springldap
Name: springldap
Namespace: default
Priority: 0
PriorityClassName: <none>
Node: minikube/192.168.0.21
Start Time: Tue, 19 Feb 2019 23:47:12 +0000
Labels: run=springldap
Annotations: <none>
Status: Running
IP: 172.17.0.5
Containers:
springldap:
Container ID: docker://59d3327a4135b62a7d5d01a9b0cb3923953757f6ba1845647f9c49ded5b97205
Image: localhost:5000/dev/ramays/springldap
Image ID: docker-pullable://localhost:5000/dev/ramays/springldap@sha256:3141232e1e660a788bf14f83d97ed4e1c240f1691c779fd7ac2fc8bee076a7f4
Port: 9090/TCP
Host Port: 0/TCP
State: Running
Started: Tue, 19 Feb 2019 23:47:13 +0000
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-rbxnm (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
default-token-rbxnm:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-rbxnm
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 3m3s default-scheduler Successfully assigned default/springldap to minikube
Normal Pulling 3m2s kubelet, minikube pulling image "localhost:5000/dev/ramays/springldap"
Normal Pulled 3m2s kubelet, minikube Successfully pulled image "localhost:5000/dev/ramays/springldap"
Normal Created 3m2s kubelet, minikube Created container
Normal Started 3m2s kubelet, minikube Started container
$ curl http://172.17.0.5:9090
<!DOCTYPE html>.....Check Services - Pods
$ kubectl get podsCheck Services - ReplicaSets
$ kubectl get rsCheck Services
$ kubectl get servicesPod information
$ kubectl get pods -o wide
$ kubectl describe pod springldap-xxxxx
$ kubectl get po springldap-xxxxx -o yamlMeta Information
$ kubectl explain pods
$ kubectl explain pods.specCleanUp
$ kubectl delete all --all
pod "springldap-cdxlk" deleted
pod "springldap-cgjsl" deleted
pod "springldap-lw48v" deleted
replicationcontroller "springldap" deleted
service "kubernetes" deleted <-- will be recreated!
service "springldap-nodeport" deletedapiVersion: v1
kind: Pod
metadata:
name: springldap-manual
spec:
containers:
- image: localhost:5000/dev/ramays/springldap
name: springldap
ports:
- containerPort: 9090
protocol: TCP$ kubectl create -f springldap-manual.yamlCreate a ReplicaSet, which will automatically create the pods. Note that ReplicationControllers are deprecated.
apiVersion: apps/v1
kind: ReplicaSet
metadata:
name: springldap
spec:
replicas: 3
selector:
matchLabels:
app: springldap
template:
metadata:
labels:
app: springldap
spec:
containers:
- name: springldap
image: localhost:5000/dev/ramays/springldap
ports:
- containerPort: 9090$ kubectl create -f springldap-rs.yaml
$ kubectl get pods,rs,services
NAME READY STATUS RESTARTS AGE
pod/springldap-l9vkj 1/1 Running 0 54s
pod/springldap-l9xsh 1/1 Running 0 54s
pod/springldap-vcsl4 1/1 Running 0 54s
NAME DESIRED CURRENT READY AGE
replicaset.apps/springldap 3 3 3 54s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 7m29sClean up and recreate the pods using a ReplicaSet
$ kubectl delete all --all
$ kubectl create -f springldap-rs.yamlExpose Spring Boot Pods through a Load-Balancer (not supported in Minikube v0.30.0)
$ kubectl expose rc springldap --type=LoadBalancer --name springldap-httpExpose Spring Boot Pods Through a NodePort
$ kubectl expose rc springldap --name springldap-nodeportCheck Services
$ kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 71d
springldap-nodeport ClusterIP 10.109.11.173 <none> 9090/TCP 6s
$ curl 10.109.11.173:9090Edit and update YAML
$ kubectl replace -f springldap-rs.yamlScale Up
$ kubectl scale --replicas=6 -f springldap-rs.yamlScale Up
$ kubectl scale --replicas=6 replicaset springldap Delete a Single Pod (A new one will be started by the RC)
$ kubectl delete po springldap-xxxxxDisplay Pods along with the app label
$ kubectl get pods -L app -o wideEdit RC YAML and Apply Changes
$ kubectl edit rs springldapDelete RC but Keep the Pods Runnning
$ kubectl delete rs springldap --cascade=falseapiVersion: apps/v1beta2
kind: ReplicaSet
metadata:
name: springldap
spec:
replicas: 3
selector:
matchLabels:
app: springldap
template:
metadata:
labels:
app: springldap
spec:
containers:
- name: springldap
image: localhost:5000/dev/ramays/springldapA ReplicaSet is the replacement for ReplicationControllers
$ kubectl delete all --all
$ kubectl create -f springldap-rs.yaml
$ kubectl get pods,rs,services
NAME READY STATUS RESTARTS AGE
pod/springldap-4m5bk 1/1 Running 0 10s
pod/springldap-n5r6p 1/1 Running 0 10s
pod/springldap-zspzn 1/1 Running 0 10s
NAME DESIRED CURRENT READY AGE
replicaset.apps/springldap 3 3 3 10s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 23sapiVersion: v1
kind: Service
metadata:
name: springldap
spec:
ports:
- port: 80
targetPort: 9090
selector:
app: springldap$ kubectl delete all --all
$ kubectl create -f springldap-svc.yaml
service/springldap created
$ kubectl get pods,rc,services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 37s
service/springldap ClusterIP 10.107.146.119 <none> 80/TCP 3sNote that only the service is created and no backing pods so curl at the service address does not do anything
$ curl 10.107.146.119
curl: (7) Failed to connect to 10.107.146.119 port 80: Connection refusedService is targeted at port 9090 of the pods
$ kubectl describe service/springldap
Name: springldap
Namespace: default
Labels: <none>
Annotations: <none>
Selector: app=springldap
Type: ClusterIP
IP: 10.107.146.119
Port: <unset> 80/TCP
TargetPort: 9090/TCP
Endpoints: <none>
Session Affinity: None
Events: <none>Create the ReplicaSet which will create the pods
$ kubectl create -f springldap-rs.yaml
replicaset.apps/springldap created
$ kubectl get pods,rs,services
NAME READY STATUS RESTARTS AGE
pod/springldap-nz8hx 1/1 Running 0 9s
pod/springldap-s2xjz 1/1 Running 0 9s
pod/springldap-t5r4d 1/1 Running 0 9s
NAME DESIRED CURRENT READY AGE
replicaset.extensions/springldap 3 3 3 9s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3m48s
service/springldap ClusterIP 10.107.146.119 <none> 80/TCP 3m14sNow we can invoke the spring boot service - note that this does not work from another machine
$ curl 10.107.146.119
<!DOCTYPE html>.....$ curl 10.101.78.142 (does not work externally)Get the environment for a particular Pod which will show the host and port that exposes this Pod through a Service.
$ kubectl get po
NAME READY STATUS RESTARTS AGE
pod/springldap-nz8hx 1/1 Running 0 9s
pod/springldap-s2xjz 1/1 Running 0 9s
pod/springldap-t5r4d 1/1 Running 0 9s
$ kubectl exec springldap-nz8hx env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/opt/jdk/bin
HOSTNAME=springldap-rkbfp
SPRINGLDAP_PORT_80_TCP_PORT=80
SPRINGLDAP_SERVICE_HOST=10.106.116.230 <----
SPRINGLDAP_SERVICE_PORT=80 <----
SPRINGLDAP_PORT_80_TCP=tcp://10.106.116.230:80
SPRINGLDAP_PORT_80_TCP_ADDR=10.106.116.230
KUBERNETES_SERVICE_HOST=10.96.0.1 <----
KUBERNETES_SERVICE_PORT=443 <----
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
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_SERVICE_PORT_HTTPS=443
SPRINGLDAP_PORT=tcp://10.106.116.230:80
SPRINGLDAP_PORT_80_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_PORT=443
JAVA_VERSION_MAJOR=8
JAVA_VERSION_MINOR=192
JAVA_VERSION_BUILD=12
JAVA_PACKAGE=server-jre
JAVA_JCE=standard
JAVA_HOME=/opt/jdk
GLIBC_REPO=https://github.com/sgerrand/alpine-pkg-glibc
GLIBC_VERSION=2.28-r0
LANG=C.UTF-8
HOME=/rootNote that all services are available through environment variables. So if a mydatabase service is created, for example, that will be available through MYDATABASE_SERVICE_HOST and MYDATABASE_SERVICE_PORT
You cannot ping a Service IP because it is a virtual IP address and has no meaning without the port
$ curl 10.106.116.230
<!DOCTYPE html><html....
$ ping 10.106.116.230
PING 10.106.116.230 (10.106.116.230) 56(84) bytes of data.
^C
--- 10.106.116.230 ping statistics ---
7 packets transmitted, 0 received, 100% packet loss, time 6131msThe Service can be exposed as a LoadBalancer, a NodePort or through an Ingress Service
For a NodePort Service, each cluster node open a port on the node itself will redirect traffic received on that cluster node to the underlying Service. Then the Service is accessible through a dedicated port on all nodes. The NodePort values are from 30000 to 32768
apiVersion: v1
kind: Service
metadata:
name: springldap-nodeport
spec:
type: NodePort
ports:
- port: 80
targetPort: 9090
nodePort: 30090
selector:
app: springldapNote that minikube only has a single node.
$ kubectl get -o wide nodes
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
minikube Ready master 88d v1.13.3 192.168.0.21 <none> Ubuntu 18.04.1 LTS 4.15.0-45-generic docker://18.9.1
$ curl 192.168.0.21:30090
<!DOCTYPE html><html lang="en">....
$ kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 5d16h
springldap ClusterIP 10.106.116.230 <none> 80/TCP 5d16h
springldap-nodeport NodePort 10.110.130.36 <none> 80:30090/TCP 5m21s
$ curl 10.110.130.36
<!DOCTYPE html><html lang="en">....The same would work for all Node IP addresses at port 30090
Kubernetes allows configuration options to be separated out into ConfigMaps, simple maps with key value pairs in which the values can be literals to files, which the application does not need to be aware of. The contents of the map are made available to the containers as environment variables or as files in a volume.
$ kubectl create configmap spring-ldap-configmap --from-literal=database-name=MYDB$ kubectl create configmap spring-ldap-configmap --from-file=application.propertiesapiVersion: v1
kind: Pod
metadata:
name: springldap-manual
spec:
containers:
- image: localhost:5000/dev/ramays/springldap
env: <----
- name : INTERVAL <----
valueFrom: <----
configMapKeyRef: <----
name: spring-ldap-configmap <----
key: database-name <----
name: springldap
ports:
- containerPort: 9090
protocol: TCPThe prefix is optional but useful for grouping config entries.
apiVersion: v1
kind: Pod
metadata:
name: springldap-manual
spec:
containers:
- image: localhost:5000/dev/ramays/springldap
envFrom: <----
- prefix: CONFIG_ <----
configMapRef: <----
name: spring-ldap-configmap <----
name: springldap
ports:
- containerPort: 9090
protocol: TCPkubectl create secret generic spring-ldap-secret --from-literal=database-password=abc123 env:
- name : DATABASE-PASSWORD
valueFrom:
configMapKeyRef:
name: spring-ldap-secret
key: database-passwordThis method is no longer recommended but is described here for completeness. In order to update a Replica Set from image v1 to image v2, you can use the kubectl rolling-update command. Let's say that you have an application with a Service (not shown) whose pods are created with the following ReplicaSet.
apiVersion: apps/v1beta2
kind: ReplicaSet
metadata:
name: springldap-v1
spec:
replicas: 3
selector:
matchLabels:
app: springldap
template:
metadata:
labels:
app: springldap
spec:
containers:
- name: springldap
image: localhost:5000/dev/ramays/springldap:v1If you want to update the image from v1 to v2 then run the following command.
$ kubectl rolling-update springldap-v1 springldap-v2 --image=localhost:5000/dev/ramays/springldap:v2This command will create a new ReplicaSet that is a copy of the original ReplicaSet with the image updated. The command will then scale down the pods of the original ReplicaSet and scale up the pods of the new ReplicaSet until just the new ReplicaSet pods remain.
This approach is not recommended because it relies on the client to co-ordinate the change and not the server, and because it involves changing an existing ReplicaSet rather then creating and deploying a new one.
A Deployment is a high level resource compared to ReplicaSets and Pods which are considered to be lower level resources. When you create a Deployment, a ReplicaSet is created which will create the Pods. So Deployments indirectly create Pods.
Official Kubernetes documentation recommends the use of Deployments over ReplicaSets directly.
apiVersion: apps/v1
kind: Deployment
metadata:
name: springldap
spec:
replicas: 3
template:
metadata:
labels:
app: springldap
spec:
containers:
- name: springldap
image: localhost:5000/dev/ramays/springldap
ports:
- containerPort: 9090$ kubectl create -f springldap-deployment.yaml$ kubectl get po,rs,deployment
NAME READY STATUS RESTARTS AGE
pod/springldap-66886d747c-555xr 1/1 Running 0 5m16s
pod/springldap-66886d747c-bjcpv 1/1 Running 0 5m16s
pod/springldap-66886d747c-l2grh 1/1 Running 0 5m16s
NAME DESIRED CURRENT READY AGE
replicaset.extensions/springldap-66886d747c 3 3 3 5m16s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.extensions/springldap 3/3 3 3 5m16s$ kubectl rollout status deployment.extensions/springldap
deployment "springldap" successfully rolled outNote that the deployment will not create a Service. You can create the Service using the sample above and it will connect to the Pods created by the Deployment by the label selector.
To trigger an update simply update the image in the deployment
$ kubectl set image deployment springldap springldap=localhost:5000/dev/ramays/springldap:v2Note that the old ReplicaSet is stil there.
$ kubectl get po,rs,svc,deployment
NAME READY STATUS RESTARTS AGE
pod/springldap-79587c76d7-hvlqk 1/1 Running 0 31s
pod/springldap-79587c76d7-lr5f4 1/1 Running 0 29s
pod/springldap-79587c76d7-tqgxv 1/1 Running 0 26s
NAME DESIRED CURRENT READY AGE
replicaset.extensions/springldap-66886d747c 0 0 0 20m <-- OLD
replicaset.extensions/springldap-79587c76d7 3 3 3 31s <-- NEW
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 22m
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.extensions/springldap 3/3 3 3 20m
If there is an error with the new application, the rollout can be undone just as easily
$ kubectl rollout undo deployment springldap