我是前端/后端/ DevOps 的新手。但是我需要使用 Kubernetes 在 Google Cloud Platform (GCP) 上部署應用程式以提供服務。然后我按照這一系列教程開始學習：
- https://mickeyabhi1999.medium.com/build-and-deploy-a-web-app-with-react-flask-nginx-postgresql-docker-and-google-kubernetes-e586de159a4d
- https://medium.com/swlh/build-and-deploy-a-web-app-with-react-flask-nginx-postgresql-docker-and-google-kubernetes-341f3b4de322
而本系列教程的代碼在這里：https : //github.com/abhiChakra/Addition-App
一切都很好，直到最后一步：使用“gcloud builds submit ...”來構建
- nginx 反應服務
- 燒瓶 wsgi服務
- nginx react 部署
- 在 GCP 集群上部署flask wsgi。
1.~3. 進展順利，他們的狀態是“OK”。但是多次重啟后flask wsgi部署的狀態還是“沒有最低可用性”。
我使用了“kubectl get pods”，看到flask pod 的狀態是“CrashLoopBackOff”。然后我按照這里建議的除錯程序進行操作：https : //containersolutions.github.io/runbooks/posts/kubernetes/crashloopbackoff/
我使用“kubectl describe pod flask”來查看flask pod的問題。然后我發現“退出代碼”是 139 并且有訊息“Liveness probe failed: Get "http://10.24.0.25:8000/health": read tcp 10.24.0.1:55470->10.24.0.25:8000: read : connection reset by peer”和“Readiness probe failed: Get "http://10.24.0.25:8000/ready": read tcp 10.24.0.1:55848->10.24.0.25:8000: read: connection reset by peer”。
完整的日志：
Name: flask-676d5dd999-cf6kt
Namespace: default
Priority: 0
Node: gke-addition-app-default-pool-89aab4fe-3l1q/10.140.0.3
Start Time: Thu, 11 Nov 2021 19:06:24 0800
Labels: app.kubernetes.io/managed-by=gcp-cloud-build-deploy
component=flask
pod-template-hash=676d5dd999
Annotations: <none>
Status: Running
IP: 10.24.0.25
IPs:
IP: 10.24.0.25
Controlled By: ReplicaSet/flask-676d5dd999
Containers:
flask:
Container ID: containerd://5459b747e1d44046d283a46ec1eebb625be4df712340ff9cf492d5583a4d41d2
Image: gcr.io/peerless-garage-330917/addition-app-flask:latest
Image ID: gcr.io/peerless-garage-330917/addition-app-flask@sha256:b45d25ffa8a0939825e31dec1a6dfe84f05aaf4a2e9e43d35084783edc76f0de
Port: 8000/TCP
Host Port: 0/TCP
State: Running
Started: Fri, 12 Nov 2021 17:24:14 0800
Last State: Terminated
Reason: Error
Exit Code: 139
Started: Fri, 12 Nov 2021 17:17:06 0800
Finished: Fri, 12 Nov 2021 17:19:06 0800
Ready: False
Restart Count: 222
Limits:
cpu: 1
Requests:
cpu: 400m
Liveness: http-get http://:8000/health delay=120s timeout=1s period=5s #success=1 #failure=3
Readiness: http-get http://:8000/ready delay=120s timeout=1s period=5s #success=1 #failure=3
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-s97x5 (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-s97x5:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-s97x5
Optional: false
QoS Class: Burstable
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning Unhealthy 9m7s (x217 over 21h) kubelet (combined from similar events): Liveness probe failed: Get "http://10.24.0.25:8000/health": read tcp 10.24.0.1:48636->10.24.0.25:8000: read: connection reset by peer
Warning BackOff 4m38s (x4404 over 22h) kubelet Back-off restarting failed container
按照此處的建議：https : //containersolutions.github.io/runbooks/posts/kubernetes/crashloopbackoff/#step-4 我已將“initialDelaySeconds”增加到 120，但它仍然失敗。
因為我確保我的本地筆記本電腦上一切正常，所以我認為可能存在一些連接或身份驗證問題。
更詳細地說，deployment.yaml 看起來像：
apiVersion: v1
kind: Service
metadata:
name: ui
spec:
type: LoadBalancer
selector:
app: react
tier: ui
ports:
- port: 8080
targetPort: 8080
---
apiVersion: v1
kind: Service
metadata:
name: flask
spec:
type: ClusterIP
selector:
component: flask
ports:
- port: 8000
targetPort: 8000
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: flask
spec:
replicas: 1
selector:
matchLabels:
component: flask
template:
metadata:
labels:
component: flask
spec:
containers:
- name: flask
image: gcr.io/peerless-garage-330917/addition-app-flask:latest
imagePullPolicy: "Always"
resources:
limits:
cpu: "1000m"
requests:
cpu: "400m"
livenessProbe:
httpGet:
path: /health
port: 8000
initialDelaySeconds: 30
periodSeconds: 5
readinessProbe:
httpGet:
path: /ready
port: 8000
initialDelaySeconds: 30
periodSeconds: 5
ports:
- containerPort: 8000
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: ui
spec:
replicas: 1
selector:
matchLabels:
app: react
tier: ui
template:
metadata:
labels:
app: react
tier: ui
spec:
containers:
- name: ui
image: gcr.io/peerless-garage-330917/addition-app-nginx:latest
imagePullPolicy: "Always"
resources:
limits:
cpu: "1000m"
requests:
cpu: "400m"
livenessProbe:
httpGet:
path: /health
port: 8080
initialDelaySeconds: 30
periodSeconds: 5
readinessProbe:
httpGet:
path: /ready
port: 8080
initialDelaySeconds: 30
periodSeconds: 5
ports:
- containerPort: 8080
docker-compose.yaml：
# we will be creating these services
services:
flask:
# Note that we are building from our current terminal directory where our Dockerfile is located, we use .
build: .
# naming our resulting container
container_name: flask
# publishing a port so that external services requesting port 8000 on your local machine
# are mapped to port 8000 on our container
ports:
- "8000:8000"
nginx:
# Since our Dockerfile for web-server is located in react-app foler, our build context is ./react-app
build: ./react-app
container_name: nginx
ports:
- "8080:8080"
Nginx Dockerfile：
# first building react project, using node base image
FROM node:10 as build-stage
# setting working dir inside container
WORKDIR /react-app
# required to install packages
COPY package*.json ./
# installing npm packages
RUN npm install
# copying over react source material
COPY src ./src
# copying over further react material
COPY public ./public
# copying over our nginx config file
COPY addition_container_server.conf ./
# creating production build to serve through nginx
RUN npm run build
# starting second, nginx build-stage
FROM nginx:1.15
# removing default nginx config file
RUN rm /etc/nginx/conf.d/default.conf
# copying our nginx config
COPY --from=build-stage /react-app/addition_container_server.conf /etc/nginx/conf.d/
# copying production build from last stage to serve through nginx
COPY --from=build-stage /react-app/build/ /usr/share/nginx/html
# exposing port 8080 on container
EXPOSE 8080
CMD ["nginx", "-g", "daemon off;"]
Nginx 服務器配置：
server {
listen 8080;
# location of react build files
root /usr/share/nginx/html/;
# index html from react build to serve
index index.html;
# ONLY KUBERNETES RELEVANT: endpoint for health checkup
location /health {
return 200 "health ok";
}
# ONLY KUBERNETES RELEVANT: endpoint for readiness checkup
location /ready {
return 200 "ready";
}
# html file to serve with / endpoint
location / {
try_files $uri /index.html;
}
# proxing under /api endpoint
location /api {
client_max_body_size 10m;
add_header 'Access-Control-Allow-Origin' http://<NGINX_SERVICE_ENDPOINT>:8080;
proxy_pass http://flask:8000/;
}
}
App.js 中有兩個重要的功能：
...
insertCalculation(event, calculation){
/*
Making a POST request via a fetch call to Flask API with numbers of a
calculation we want to insert into DB. Making fetch call to web server
IP with /api/insert_nums which will be reverse proxied via Nginx to the
Application (Flask) server.
*/
event.preventDefault();
fetch('http://<NGINX_SERVICE_ENDPOINT>:8080/api/insert_nums', {method: 'POST',
mode: 'cors',
headers: {
'Content-Type' : 'application/json'
},
body: JSON.stringify(calculation)}
).then((response) => {
...
getHistory(event){
/*
Making a GET request via a fetch call to Flask API to retrieve calculations history.
*/
event.preventDefault()
fetch('http://<NGINX_SERVICE_ENDPOINT>:8080/api/data', {method: 'GET',
mode: 'cors'
}
).then(response => {
...
燒瓶Dockerfile：
# using base image
FROM python:3.8
# setting working dir inside container
WORKDIR /addition_app_flask
# adding run.py to workdir
ADD run.py .
# adding config.ini to workdir
ADD config.ini .
# adding requirements.txt to workdir
ADD requirements.txt .
# installing flask requirements
RUN pip install -r requirements.txt
# adding in all contents from flask_app folder into a new flask_app folder
ADD ./flask_app ./flask_app
# exposing port 8000 on container
EXPOSE 8000
# serving flask backend through uWSGI server
CMD [ "python", "run.py" ]
運行.py：
from gevent.pywsgi import WSGIServer
from flask_app.app import app
# As flask is not a production suitable server, we use will
# a WSGIServer instance to serve our flask application.
if __name__ == '__main__':
WSGIServer(('0.0.0.0', 8000), app).serve_forever()
應用程式.py：
from flask import Flask, request, jsonify
from flask_app.storage import insert_calculation, get_calculations
app = Flask(__name__)
@app.route('/')
def index():
return "My Addition App", 200
@app.route('/health')
def health():
return '', 200
@app.route('/ready')
def ready():
return '', 200
@app.route('/data', methods=['GET'])
def data():
'''
Function used to get calculations history
from Postgres database and return to fetch call in frontend.
:return: Json format of either collected calculations or error message
'''
calculations_history = []
try:
calculations = get_calculations()
for key, value in calculations.items():
calculations_history.append(value)
return jsonify({'calculations': calculations_history}), 200
except:
return jsonify({'error': 'error fetching calculations history'}), 500
@app.route('/insert_nums', methods=['POST'])
def insert_nums():
'''
Function used to insert a calculation into our postgres
DB. Operands of operation received from frontend.
:return: Json format of either success or failure response.
'''
insert_nums = request.get_json()
firstNum, secondNum, answer = insert_nums['firstNum'], insert_nums['secondNum'], insert_nums['answer']
try:
insert_calculation(firstNum, secondNum, answer)
return jsonify({'Response': 'Successfully inserted into DB'}), 200
except:
return jsonify({'Response': 'Unable to insert into DB'}), 500
我不知道出了什么問題。我也想知道除錯這種云部署案例的更好方法是什么？因為在普通程式中，我們可以設定一些斷點并列印或記錄一些東西來檢查導致問題的代碼的根位置，但是在云部署中，我失去了除錯的方向。
uj5u.com熱心網友回復：
...Exit Code was 139...
這可能意味著您的 Flask 應用程式中存在錯誤。您可以從最低規格開始，而不是試圖在一個目標中完成所有任務：
apiVersion: v1
kind: Pod
metadata:
name: flask
labels:
component: flask
spec:
containers:
- name: flask
image: gcr.io/peerless-garage-330917/addition-app-flask:latest
ports:
- containerPort: 8000
查看您的 pod 是否相應啟動。如果是，請嘗試連接到它kubectl port-forward <flask pod name> 8000:8000，然后按curl localhost:8000/health。你應該時刻關注你的申請kubectl logs -f <flask pod name>。
uj5u.com熱心網友回復：
感謝@gohm'c 的回復！隔離不同的部分并從較小的組件開始是一個很好的建議。按照建議，我首先嘗試部署一個 Flask pod。然后我用
kubectl port-forward flask 8000:8000
將埠映射到本地機器。使用
curl localhost:8000/health
訪問埠后，顯示
Forwarding from 127.0.0.1:8000 -> 8000
Forwarding from [::1]:8000 -> 8000
Handling connection for 8000
E1112 18:52:15.874759 300145 portforward.go:400] an error occurred forwarding 8000 -> 8000: error forwarding port 8000 to pod 4870b939f3224f968fd5afa4660a5af7d10e144ee85149d69acff46a772e94b1, uid : failed to execute portforward in network namespace "/var/run/netns/cni-32f718f0-1248-6da4-c726-b2a5bf1918db": read tcp4 127.0.0.1:38662->127.0.0.1:8000: read: connection reset by peer
此時，使用
kubectl logs -f flask
回傳空回應。所以flask應用確實存在一些問題。
這個健康探測是 app.py 中一個非常簡單的函式：
@app.route('/health')
def health():
return '', 200
我如何知道路線設定是否錯誤？是不是因為run.py中的WSGIServer？
from gevent.pywsgi import WSGIServer
from flask_app.app import app
# As flask is not a production suitable server, we use will
# a WSGIServer instance to serve our flask application.
if __name__ == '__main__':
WSGIServer(('0.0.0.0', 8000), app).serve_forever()
如果我們查看 Dockerfile，它似乎暴露了正確的埠 8000。如果我直接運行
python run.py
在我的筆記本電腦上，我可以成功訪問 localhost:8000 。我該如何除錯此類問題？
轉載請註明出處，本文鏈接：https://www.uj5u.com/caozuo/357691.html
標籤：码头工人 nginx 烧瓶 Kubernetes 谷歌云平台