[Udemy] Services Demo with Cluster IP and Load Balancer Services (Imperative)

Service Demo

1. User가 http://<SVC-Public-IP>/hello로 접속

2. 해당 요청이 LoadBalancer로 전달 후, Front App(Pod)로 이동

3. Front App에 있는 Nginx 역방향 프록시 응용 프로그램의 프록시 규칙을 통해 Backend App(Pod)으로 요청 전달

4. 해당 요청을 Backend App의 Cluster IP로 전달

5. Backend App(Pod)으로 요청 완료 후 Hello World Service 출력

 

Backend Rest App 환경 구성 (Deployment / ClusterIP)

 

# Deployment 생성

# Create Deployment for Frontend Nginx Proxy
kubectl create deployment my-backend-rest-app --image=stacksimplify/kube-helloworld:1.0.0

 

해당 이미지는 stacksimplify의 Docker Hub에서 kube-helloword:1.0.0를 가져옵니다.

 

# Deployment / ReplicaSets / Pods 확인

kubectl get deploy
---
NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
my-backend-rest-app   0/1     1            0           4s

 

kubectl get replicasets
---
NAME                             DESIRED   CURRENT   READY   AGE
my-backend-rest-app-56d79d9d95   1         1         1       7m53s

kubectl get pods
---
NAME                                   READY   STATUS    RESTARTS   AGE
my-backend-rest-app-56d79d9d95-px7fh   1/1     Running   0          8m9s

 

# Backend App Pod의 로그 확인

kubectl logs -f my-backend-rest-app-56d79d9d95-px7fh
---
  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.7.RELEASE)

2025-02-13 06:30:42.428  INFO 1 --- [           main] c.s.helloworld.HelloworldApplication     : Starting HelloworldApplication v1.0.0 on my-backend-rest-app-56d79d9d95-px7fh with PID 1 (/app.jar started by root in /)
2025-02-13 06:30:42.443  INFO 1 --- [           main] c.s.helloworld.HelloworldApplication     : No active profile set, falling back to default profiles: default
2025-02-13 06:30:45.545  INFO 1 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2025-02-13 06:30:45.572  INFO 1 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]        
2025-02-13 06:30:45.572  INFO 1 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.34]
2025-02-13 06:30:45.705  INFO 1 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2025-02-13 06:30:45.706  INFO 1 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 2933 ms
2025-02-13 06:30:46.133  INFO 1 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2025-02-13 06:30:46.537  INFO 1 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2025-02-13 06:30:46.543  INFO 1 --- [           main] c.s.helloworld.HelloworldApplication     : Started HelloworldApplication in 5.772 seconds (JVM running for 6.935)

 

# Backend App의 Deployment를 Service를 통해 노출

kubectl expose deployment my-backend-rest-app --port=8080 --target-port=8080 --name=my-backend-service
---
service/my-backend-service exposed

 

port도 8080, target port도 8080이다.

* Service 생성 시, type을 명시하지 않으면 기본 값은 ClusterIP이다.

 

Observation: We don't need to specify "--type=ClusterIp" because default setting is to create ClusterIp Service.

 

# Backend App의 Service 확인

kubectl get svc
---
NAME                 TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)    AGE
kubernetes           ClusterIP   10.0.0.1     <none>        443/TCP    25h
my-backend-service   ClusterIP   10.0.51.67   <none>        8080/TCP   36s

 

type은 ClusterIP 서비스로, 포트는 8080으로 생성되었다.

 

Frontend Rest App 환경 구성 (Deployment / LoadBalancer)

 

# Deployment 생성

# Create Deployment for Frontend Nginx Proxy
kubectl create deployment my-frontend-nginx-app --image=stacksimplify/kube-frontend-nginx:1.0.0

 

** Frontend App 내 Nginx 역방향 프록시 구성은, 컨테이너 이미지(stacksimplify/kube-frontend-nginx:1.0.0) 안에 이미 포함되어있다.

** 코드 내용을 보면, http://<my-frontend-service>:80 으로 요청오면, Nginx 역방향 프록시에 의해 http://<my-frontend-service>:8080으로 전달된다.

 

- **Important Note:** In Nginx reverse proxy, ensure backend service name `my-backend-service` is updated when you are building the frontend container. We already built it and put ready for this demo (stacksimplify/kube-frontend-nginx:1.0.0)

- **Nginx Conf File**

```conf

server {

    listen       80;

    server_name  localhost;

    location / {

    # Update your backend application Kubernetes Cluster-IP Service name  and port below      

    # proxy_pass http://<Backend-ClusterIp-Service-Name>:<Port>;      

    proxy_pass http://my-backend-service:8080;

    }

    error_page   500 502 503 504  /50x.html;

    location = /50x.html {

        root   /usr/share/nginx/html;

    }

}

```

 

# Deployment / ReplicaSets / Pods 확인

kubectl get deploy
---
NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
my-backend-rest-app     1/1     1            1           20m
my-frontend-nginx-app   1/1     1            1           97s

 

frontend app / Backend app의 Deployment가 배포되어 있는 것을 확인 가능

 

kubectl get replicasets
---
NAME                               DESIRED   CURRENT   READY   AGE
my-backend-rest-app-56d79d9d95     1         1         1       21m
my-frontend-nginx-app-645fdcc6d7   1         1         1       3m10s

kubectl get pods
---
NAME                                     READY   STATUS    RESTARTS   AGE
my-backend-rest-app-56d79d9d95-px7fh     1/1     Running   0          22m
my-frontend-nginx-app-645fdcc6d7-6rptq   1/1     Running   0          3m29s

 

# Frontend App의 Deployment를 Service를 통해 노출

kubectl expose deployment my-frontend-nginx-app  --type=LoadBalancer --port=80 --target-port=80 --name=my-frontend-service
---
service/my-frontend-service exposed

 

type은 LoadBalancer, port는 80, target port도 80으로 expose한다.

 

# Frontend App의 Service 확인

kubectl get svc
---
NAME                  TYPE           CLUSTER-IP    EXTERNAL-IP     PORT(S)        AGE
kubernetes            ClusterIP      10.0.0.1      <none>          443/TCP        26h
my-backend-service    ClusterIP      10.0.51.67    <none>          8080/TCP       13m
my-frontend-service   LoadBalancer   10.0.234.34   20.249.170.66   80:30311/TCP   2m20s

 

Frontend App의 LoadBalance가 잘 생성 되었다.

Frontend App의 External IP로 접속해보자.

정상적으로 접근 가능하다.

 

# scale up

kubectl scale --replicas=10 deployment/my-backend-rest-app

 

10개로 scale up 했다.

 

kubectl get deploy
---
NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
my-backend-rest-app     10/10   10           10          29m
my-frontend-nginx-app   1/1     1            1           10m

kubectl get rs
---
NAME                               DESIRED   CURRENT   READY   AGE
my-backend-rest-app-56d79d9d95     10        10        10      29m
my-frontend-nginx-app-645fdcc6d7   1         1         1       10m

kubectl get pods
---
NAME                                     READY   STATUS    RESTARTS   AGE
my-backend-rest-app-56d79d9d95-clrxr     1/1     Running   0          54s
my-backend-rest-app-56d79d9d95-dvtkf     1/1     Running   0          54s
my-backend-rest-app-56d79d9d95-fcrvw     1/1     Running   0          54s
my-backend-rest-app-56d79d9d95-j5wft     1/1     Running   0          54s
my-backend-rest-app-56d79d9d95-jz222     1/1     Running   0          54s
my-backend-rest-app-56d79d9d95-lpmkj     1/1     Running   0          54s
my-backend-rest-app-56d79d9d95-mbdmn     1/1     Running   0          54s
my-backend-rest-app-56d79d9d95-p8jlc     1/1     Running   0          54s
my-backend-rest-app-56d79d9d95-psvxg     1/1     Running   0          54s
my-backend-rest-app-56d79d9d95-px7fh     1/1     Running   0          29m
my-frontend-nginx-app-645fdcc6d7-6rptq   1/1     Running   0          10m

 

# 확인

http://<External-IP-from-get-service-output>/hello로 접근 시,

Load Balancer에 의해 Pod의 부하 분산이 이루어 지는 것을 확인 가능 

 

---

[참고 영상]

Udemy - Azure Kubernetes Service with Azure DevOps and Terraform

섹션 4 : Kubernetes Fundamentals with kubectl - Imperative Approach

34. Step-17: Introduction to Services in Kubernetes

35. Step-18: Services Demo with Cluster IP and Load Balancer Services

 

 

[참고 문서]

https://github.com/stacksimplify/azure-aks-kubernetes-masterclass/tree/master/03-Kubernetes-Fundamentals-with-kubectl/03-04-Services-with-kubectl