K8s 練習 - part 3

May 02, 2019 K8s

前言

前面玩過Dockerfile後，接下來就來結合K8s來玩玩瞜~

前置作業

Dockerfile

# Use an official Python runtime as a parent image
FROM python:2.7-slim

# Set the working directory to /app
WORKDIR /app

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

# Install any needed packages specified in requirements.txt
RUN pip install --trusted-host pypi.python.org -r requirements.txt

# Make port 80 available to the world outside this container
EXPOSE 80

# Define environment variable
ENV NAME World
ENV TAG  v1

# Run app.py when the container launches
CMD ["python", "app.py"]

requirements.txt

Flask
Redis

app.py

from flask import Flask
from redis import Redis, RedisError
import os
import socket

# Connect to Redis
redis = Redis(host="redis", db=0, socket_connect_timeout=2, socket_timeout=2)

app = Flask(__name__)

@app.route("/")
def hello():
    try:
        visits = redis.incr("counter")
    except RedisError:
        visits = "<i>cannot connect to Redis, counter disabled</i>"

    html = "<h3>Hello {name}!</h3>" \
           "<b>Hostname:</b> {hostname}<br/>" \
           "<b>Tag:</b> {tag}<br/>" \
           "<b>Visits:</b> {visits}"
    return html.format(name=os.getenv("NAME", "world"), name=os.getenv("TAG", "v0"), hostname=socket.gethostname(), visits=visits)

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=80)

建立2個Tag版本並把它傳上Docker Hub
我這邊範例是用v1, v2

$ docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
friendlyhello       v1                  481ef22c534e        40 minutes ago      131MB

$ docker tag friendlyhello:v1 zondayang/flask_demo:v1

$ docker images
REPOSITORY             TAG                 IMAGE ID            CREATED             SIZE
friendlyhello          v1                  481ef22c534e        41 minutes ago      131MB
zondayang/flask_demo   v1                  481ef22c534e        41 minutes ago      131MB

$ docker push zondayang/flask_demo:v1

K8s

run v1

$ kubectl run flask-demo --image=docker.io/zondayang/flask_demo:v1 --port 80
kubectl run --generator=deployment/apps.v1 is DEPRECATED and will be removed in a future version. Use kubectl run --generator=run-pod/v1 or kubectl create instead.
deployment.apps/flask-demo created

$ kubectl get pods
NAME                              READY   STATUS    RESTARTS   AGE
flask-demo-766b9f4bc8-5t7s6       1/1     Running   0          16s
hello-minikube-56cdb79778-trxx9   1/1     Running   1          9h

$ kubectl expose deployment/flask-demo --type=NodePort --port 80 
service/flask-demo exposed

$ kubectl get services
NAME             TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
flask-demo       NodePort    10.109.241.127   <none>        80:30521/TCP     9s
hello-minikube   NodePort    10.103.163.153   <none>        8080:30337/TCP   9h
kubernetes       ClusterIP   10.96.0.1        <none>        443/TCP          20h

$ minikube service flask-demo --url
http://192.168.99.100:30521

deployments

觀看deployments的訊息，以及產生副本

$ kubectl get deployments
NAME             READY   UP-TO-DATE   AVAILABLE   AGE
flask-demo       1/1     1            1           8m25s
hello-minikube   1/1     1            1           9h

$ kubectl scale deployment/flask-demo --replicas=2
deployment.extensions/flask-demo scaled

$ kubectl get deployments
NAME             READY   UP-TO-DATE   AVAILABLE   AGE
flask-demo       2/2     2            2           9m47s
hello-minikube   1/1     1            1           9h

更新版本:

$ kubectl set image deployment/flask-demo flask-demo=docker.io/zondayang/flask_demo:v2

Undo:

$ kubectl rollout status deployment/flask-demo
deployment "flask-demo" successfully rolled out


$ kubectl rollout history deployment/flask-demo
deployment.extensions/flask-demo 
REVISION  CHANGE-CAUSE
1         <none>
2         <none>

$ kubectl rollout undo deployment/flask-demo
deployment.extensions/flask-demo rolled back

$ kubectl rollout history deployment/flask-demo
deployment.extensions/flask-demo 
REVISION  CHANGE-CAUSE
2         <none>
3         <none>

查看詳細訊息:

$ kubectl describe deployment/flask-demo
Name:                   flask-demo
Namespace:              default
CreationTimestamp:      Thu, 02 May 2019 20:31:57 +0800
Labels:                 run=flask-demo
Annotations:            deployment.kubernetes.io/revision: 3
Selector:               run=flask-demo
Replicas:               2 desired | 2 updated | 2 total | 2 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  run=flask-demo
  Containers:
   flask-demo:
    Image:        docker.io/zondayang/flask_demo:v1
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   flask-demo-766b9f4bc8 (2/2 replicas created)
Events:
  Type    Reason             Age                From                   Message
  ----    ------             ----               ----                   -------
  Normal  ScalingReplicaSet  20m                deployment-controller  Scaled up replica set flask-demo-94c5457c to 1
  Normal  ScalingReplicaSet  19m                deployment-controller  Scaled down replica set flask-demo-766b9f4bc8 to 1
  Normal  ScalingReplicaSet  19m                deployment-controller  Scaled up replica set flask-demo-94c5457c to 2
  Normal  ScalingReplicaSet  19m                deployment-controller  Scaled down replica set flask-demo-766b9f4bc8 to 0
  Normal  ScalingReplicaSet  14m (x2 over 25m)  deployment-controller  Scaled up replica set flask-demo-766b9f4bc8 to 1
  Normal  ScalingReplicaSet  14m (x2 over 21m)  deployment-controller  Scaled up replica set flask-demo-766b9f4bc8 to 2
  Normal  ScalingReplicaSet  14m                deployment-controller  Scaled down replica set flask-demo-94c5457c to 1
  Normal  ScalingReplicaSet  14m                deployment-controller  Scaled down replica set flask-demo-94c5457c to 0

Reference

Kubernete概念解析之Deployment