I am trying to access a Postgresql database from within a Kubernets cluster with the following configuration (inspired by the documentation from /).

The database that I am trying to use runs on my localhost at address 192.168.1.177 port 54322, outside the cluster (Minikube).

---
# Source: external-postgresql/templates/service-entry.yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: sample-external-postgresql
  namespace: sample
  labels:
    helm.sh/chart: external-postgresql-0.1.0
    app.kubernetes.io/name: external-postgresql
    app.kubernetes.io/instance: sample
    app.kubernetes.io/version: "0.0.1"
    app.kubernetes.io/managed-by: Helm
spec:
  hosts:
    - postgres
  addresses:
    - 192.168.1.177/16
  ports:
    - number: 54322
      name: postgresql
      protocol: TCP
  location: MESH_EXTERNAL
  resolution: STATIC
---
# Source: external-postgresql/templates/virtual-service.yaml
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: sample-external-postgresql
  namespace: sample
  labels:
    helm.sh/chart: external-postgresql-0.1.0
    app.kubernetes.io/name: external-postgresql
    app.kubernetes.io/instance: sample
    app.kubernetes.io/version: "0.0.1"
    app.kubernetes.io/managed-by: Helm
spec:
  hosts:
    - postgres
  http:
    - name: "external-postgresql"
      match:
        - uri:
            prefix: "/"
      route:
        - destination:
            host: postgres

The consuming Java (minimalistic SpringBoot) based Restful application gets configured to open the database connection with 'jdbc:postgresql://postgres:54322/postgres'. I am deploying that container with the following object

# Source: training-restful/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: sample-training-restful
  namespace: sample
  labels:
    helm.sh/chart: training-restful-0.0.2
    app.kubernetes.io/name: training-restful
    app.kubernetes.io/instance: sample
    app.kubernetes.io/namespace: sample
    app.kubernetes.io/version: "0.3"
    app.kubernetes.io/managed-by: Helm
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: training-restful
      app.kubernetes.io/instance: sample
      app.kubernetes.io/namespace: sample
  template:
    metadata:
      labels:
        helm.sh/chart: training-restful-0.0.2
        app.kubernetes.io/name: training-restful
        app.kubernetes.io/instance: sample
        app.kubernetes.io/namespace: sample
        app.kubernetes.io/version: "0.3"
        app.kubernetes.io/managed-by: Helm
    spec:
      serviceAccountName: sample-training-restful
      securityContext:
        {}
      restartPolicy: Always
      containers:
        - name: training-restful
          securityContext:
            {}
          image: "training-app:0.3"
          imagePullPolicy: IfNotPresent
          env:
            - name: DATABASE_USER
              value: postgres
            - name: DATABASE_PASSWORD
              value: ChangeMe$191
            - name: DATABASE_URL
              value: jdbc:postgresql://postgres:54322/postgres
          ports:
            - name: http
              containerPort: 8080
              protocol: TCP
          livenessProbe:
            initialDelaySeconds: 1000
            failureThreshold: 1
            periodSeconds: 60
            terminationGracePeriodSeconds: 60
            httpGet:
              host: 127.0.0.1
              path: /v1/api/index
              port: 8080

When the pod starts-up, it writes the following traces in the log file

2025-02-06 17:53:36,670 INFO o.s.b.StartupInfoLogger [main] Starting SampleApplication v0.0.2-SNAPSHOT using Java 21.0.6 with PID 1 (/opt/app/Sample.jar started by root in /opt/app)
2025-02-06 17:53:36,674 DEBUG o.s.b.StartupInfoLogger [main] Running with Spring Boot v3.4.1, Spring v6.2.1
2025-02-06 17:53:36,674 INFO o.s.b.SpringApplication [main] The following 1 profile is active: "dev"
2025-02-06 17:53:40,975 ERROR o.h.e.j.s.SqlExceptionHelper [main] The connection attempt failed.
2025-02-06 17:53:42,506 DEBUG c.m.w.s.c.SecurityConfiguration [main] Configure the security platform
2025-02-06 17:53:42,866 INFO o.s.b.StartupInfoLogger [main] Started SampleApplication in 6.84 seconds (process running for 7.61) 

After deploying the SE and VS, running 'istioctl analyze -n sample' yields no validation issues in the log.

>istioctl analyze -n sample

✔ No validation issues found when analyzing namespace: sample.

However, the Restful application cannot connect to the external database.

I have an extra hint from Kiali, which analyzing the Virtual Service, it tells me that the host (spec.http.route.destination.host) cannot be resolved.

To test that the actual Postgres database is connectable from the Kubernetes cluster, if I hardcode its IP directly into the environment variable DATABASE_URL (as shown in the code snippet below), the connection is established right, and my sample Restful app can do all needed operation (SELECT, INSERT, UPDATE ...) without restriction

# Source: training-restful/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: sample-training-restful
  namespace: sample
  labels:
    helm.sh/chart: training-restful-0.0.2
    app.kubernetes.io/name: training-restful
    app.kubernetes.io/instance: sample
    app.kubernetes.io/namespace: sample
    app.kubernetes.io/version: "0.3"
    app.kubernetes.io/managed-by: Helm
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: training-restful
      app.kubernetes.io/instance: sample
      app.kubernetes.io/namespace: sample
  template:
    metadata:
      labels:
        helm.sh/chart: training-restful-0.0.2
        app.kubernetes.io/name: training-restful
        app.kubernetes.io/instance: sample
        app.kubernetes.io/namespace: sample
        app.kubernetes.io/version: "0.3"
        app.kubernetes.io/managed-by: Helm
    spec:
      serviceAccountName: sample-training-restful
      securityContext:
        {}
      restartPolicy: Always
      containers:
        - name: training-restful
          securityContext:
            {}
          image: "training-app:0.3"
          imagePullPolicy: IfNotPresent
          env:
            - name: DATABASE_USER
              value: postgres
            - name: DATABASE_PASSWORD
              value: ChangeMe$191
            - name: DATABASE_URL
              value: jdbc:postgresql://192.168.1.177:54322/postgres
          ports:
            - name: http
              containerPort: 8080
              protocol: TCP
          livenessProbe:
            initialDelaySeconds: 1000
            failureThreshold: 1
            periodSeconds: 60
            terminationGracePeriodSeconds: 60
            httpGet:
              host: 127.0.0.1
              path: /v1/api/index
              port: 8080

How can I configure the external database to access so that I can late make use of the goodies from Istio?

Thank you for any useful hit