Minikube Kubernetes, Postgres, Spring Boot Cluster - Postgres connection refused - postgresql

Question

so I have a basic minikube cluster configuration for K8s cluster with only 2 pods for Postgres DB and my Spring app. However, I can't get my app to connect to my DB. I know that in Docker such issue could be solved with networking but after a lot of research I can't seem to find the problem and the solution to my issue.
Currently, given my configuration I get a Connection refused error by postgres whenever my Spring App tries to start:
Caused by: org.postgresql.util.PSQLException: Connection to postgres-service:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
So my spring-app is a basic REST API with some open endpoints where I query for some data. The app works completely fine and here is my application.properties:
spring.datasource.driverClassName=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://${POSTGRES_HOST}:${POSTGRES_PORT}/${POSTGRES_DB}
spring.datasource.username=${POSTGRES_USER}
spring.datasource.password=${POSTGRES_PASSWORD}
spring.jpa.database-platform=org.hibernate.dialect.PostgreSQLDialect
spring.jpa.hibernate.ddl-auto=update
The way I create my Postgres component is by creating a ConfigMap, a Secret and finally a Deployment with it's Service inside. They look like so:
postgres-config.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: postgres-config
data:
postgres-url: postgres-service
postgres-port: "5432"
postgres-db: "test"
postgres-secret.yaml
apiVersion: v1
kind: Secret
metadata:
name: postgres-secret
type: Opaque
data:
postgres_user: cm9vdA== #already encoded in base64
postgres_password: cm9vdA== #already encoded in base64
postgres.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: postgres-deployment
labels:
app: postgres
spec:
replicas: 1
selector:
matchLabels:
app: postgres
template:
metadata:
labels:
app: postgres
spec:
containers:
- name: postgresdb
image: postgres
ports:
- containerPort: 5432
env:
- name: POSTGRES_USER
valueFrom:
secretKeyRef:
name: postgres-secret
key: postgres_user
- name: POSTGRES_PASSWORD
valueFrom:
secretKeyRef:
name: postgres-secret
key: postgres_password
- name: POSTGRES_DB
valueFrom:
configMapKeyRef:
name: postgres-config
key: postgres-db
---
apiVersion: v1
kind: Service
metadata:
name: postgres-service
spec:
selector:
app.kubernetes.io/name: postgres
ports:
- protocol: TCP
port: 5432
targetPort: 5432
and finally here's my Deployment with it's Service for my spring app
spring-app.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: spring-app-deployment
labels:
app: spring-app
spec:
replicas: 1
selector:
matchLabels:
app: spring-app
template:
metadata:
labels:
app: spring-app
spec:
containers:
- name: spring-app
image: app #image is pulled from my docker hub
ports:
- containerPort: 8080
env:
- name: POSTGRES_USER
valueFrom:
secretKeyRef:
name: postgres-secret
key: postgres_user
- name: POSTGRES_PASSWORD
valueFrom:
secretKeyRef:
name: postgres-secret
key: postgres_password
- name: POSTGRES_HOST
valueFrom:
configMapKeyRef:
name: postgres-config
key: postgres-url
- name: POSTGRES_PORT
valueFrom:
configMapKeyRef:
name: postgres-config
key: postgres-port
- name: POSTGRES_DB
valueFrom:
configMapKeyRef:
name: postgres-config
key: postgres-db
---
apiVersion: v1
kind: Service
metadata:
name: spring-app-service
spec:
type: NodePort
selector:
app.kubernetes.io/name: spring-app
ports:
- protocol: TCP
port: 8080
targetPort: 8080
nodePort: 30001

Answer 1

A connection refused means that the host you are connecting to, does not have the port you mentioned opened.
This leads me to think that the postgres pod isnt running correctly, or the service is not pointing to those pods correctly.
By checking the Yamls I can see that the service's pod selector isnt configured correctly:
The service is selecting pods with label: app.kubernetes.io/name: postgres
The deployment is configured with pods with label: app: postgres
The correct service manifest should look like:
apiVersion: v1
kind: Service
metadata:
name: postgres-service
spec:
selector:
app: postgres
ports:
- protocol: TCP
port: 5432
targetPort: 5432
You can double check that by describing the service using kubectl describe service postgres-service.
The output should contain the postgres pods IPs for Endpoints.