not showing endpoint for service in AKS and label and selectors are mis match

Question

hi i'm new to AKS (azure kubernetes service) below is my YAML which creates service(php-svc) and pod(wordpressb). there are two issues i'm facing.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: wordpressb
spec:
  replicas: 1
  selector:
    matchlabels:
      app: wordpressb
  template:
    metadata:
      labels:
        app: wordpressb
    spec:
      containers:
      - name: wordpressb
        image: acrakswordpress.azurecr.io/wordpress:v1
        ports:
          - containerPort: 80
        env:
        - name: DATABASE_HOST
          value: "<<serverName>>.mysql.database.azure.com"
        - name: DATABASE_USERNAME
          value: "<<dbName>>"
        - name: DATABASE_PASSWORD
          value: "<<dbPassword>>"
        - name: DATABASE_NAME
          value: "<<dbName>>"
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
                - key: "app"
                  operator: In
                  value: wordpressb
            topologyKey: "kubernetes.io/hostname"

apiVersion: v1
kind: Service
metadata:
  name: php-svc
spec:
  type: LoadBalancer
  ports:
    - port: 80
  selector:
    app: wordpressb

1. nothing shows up when i try to access the external IP address of service - my best guess is it's not working as there is no end point in the service - below shows when i execute kubectl describe service php-svc

Name:                     php-svc
Namespace:                default
Labels:                   <none>
Annotations:              <none>
Selector:                 app=wordpressb
Type:                     LoadBalancer
IP Family Policy:         SingleStack
IP Families:              IPv4
IP:                       10.0.74.48
IPs:                      10.0.74.48
LoadBalancer Ingress:     52.140.2.45
Port:                     <unset>  80/TCP
TargetPort:               80/TCP
NodePort:                 <unset>  30580/TCP
Endpoints:                <none>
Session Affinity:         None
External Traffic Policy:  Cluster
Events:
  Type    Reason                Age   From                Message
  ----    ------                ----  ----                -------
  Normal  EnsuringLoadBalancer  44s   service-controller  Ensuring load balancer
  Normal  EnsuredLoadBalancer   34s   service-controller  Ensured load balancer

2. base on my understanding this issue is due to label-selector mismatch. it is matching in the YAML code (mentioned above) - but mismatched when executing it - below shows when i execute kubectl describe pod wordpress-blog

Name:             wordpress-blog
Namespace:        default
Priority:         0
Service Account:  default
Node:             aks-nodepool1-41875026-vmss000000/10.224.0.5
Start Time:       Sun, 19 May 2024 21:48:19 +0530
Labels:           run=wordpress-blog
Annotations:      <none>
Status:           Running
IP:               10.244.1.17
IPs:
  IP:  10.244.1.17
Containers:
  wordpress-blog:
    Container ID:   containerd://758ad6ebc7cb0603e0bfed305070a3c990b6cc318069c73fb1649ec1555183a7
    Image:          wordpress
    Image ID:       docker.io/library/wordpress@sha256:f468bab53528df6f87dfe11a80de26eff57e0f515e243d9dec73a02c80c273a7
    Port:           <none>
    Host Port:      <none>
    State:          Running
      Started:      Sun, 19 May 2024 21:48:22 +0530
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-jfb56 (ro)
Conditions:
  Type              Status
  Initialized       True
  Ready             True
  ContainersReady   True
  PodScheduled      True
Volumes:
  kube-api-access-jfb56:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:                      <none>

ideally i should see wordpress page when i try to hit external IP address of the service (php-svc)

Answer 1

As already discussed, your deployment YAML had a typo in the selector field. matchlabels should be matchLabels (note the capitalization of 'L'). As you have fixed that and still not getting the external IP, I am sharing you the yaml files for your ease of setup.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
      - image: mysql:5.7
        name: mysql
        env:
        - name: MYSQL_ROOT_PASSWORD
          value: rootpassword
        - name: MYSQL_DATABASE
          value: wordpress
        - name: MYSQL_USER
          value: wordpress
        - name: MYSQL_PASSWORD
          value: wordpresspassword
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim
---
apiVersion: v1
kind: Service
metadata:
  name: mysql
spec:
  ports:
    - port: 3306
  selector:
    app: mysql

Create WordPress Deployment and Service YAML

apiVersion: apps/v1
kind: Deployment
metadata:
  name: wordpressb
spec:
  replicas: 1
  selector:
    matchLabels:
      app: wordpressb
  template:
    metadata:
      labels:
        app: wordpressb
    spec:
      containers:
      - name: wordpressb
        image: arkoacr.azurecr.io/wordpress:v1
        ports:
        - containerPort: 80
        env:
        - name: WORDPRESS_DB_HOST
          value: mysql.default.svc.cluster.local:3306
        - name: WORDPRESS_DB_USER
          value: wordpress
        - name: WORDPRESS_DB_PASSWORD
          value: wordpresspassword
        - name: WORDPRESS_DB_NAME
          value: wordpress

service

apiVersion: v1
kind: Service
metadata:
  name: php-svc
spec:
  type: LoadBalancer
  ports:
    - port: 80
      targetPort: 80
  selector:
    app: wordpressb

apply them

kubectl apply -f mysql-deployment.yaml
kubectl apply -f wordpress-deployment.yaml
kubectl apply -f service.yaml

it should work.

Check service

kubectl get svc| grep php

By ensuring the correct labels and selectors match between the Deployment and Service, your Service should properly route traffic to the correct Pods.

References:

• Troubleshoot network problems in AKS clusters
• Creating a Service