Access external database from Kubernetes - postgresql

Question

I have a kubernetes (v1.18.6) with 1 service (loadbalancer), 2 pods in a develoment:
apiVersion: v1
kind: Service
metadata:
name: app-service
spec:
selector:
app: app
ports:
- protocol: "TCP"
port: 6000
targetPort: 5000
type: LoadBalancer
A network policy to access Intenert (it is necesary for me):
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: internet-access
spec:
podSelector:
matchLabels:
networking/allow-internet-access: "true"
policyTypes:
- Ingress
- Egress
ingress:
- {}
Deployment config file
apiVersion: apps/v1
kind: Deployment
metadata:
name: app-deployment
spec:
progressDeadlineSeconds: 120
selector:
matchLabels:
app: app
replicas: 2
template:
metadata:
labels:
app: app
spec:
imagePullSecrets:
- name: myregistrykey
containers:
- name: app
image: app
imagePullPolicy: Always
ports:
- containerPort: 5000
It is working correctly. But now, I want to connect this imagen to an external database (in another network only access by internet). For this proposition I use this service:
apiVersion: v1
kind: Service
metadata:
name: postgresql
spec:
clusterIP: None
ports:
- port: 25060
---
apiVersion: v1
kind: Endpoints
metadata:
name: postgresql
subsets:
- addresses:
- ip: 206............
ports:
- port: 25060
name: postgresql
It is all the services:
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
app-service LoadBalancer 10.245.134.137 206........... 6000:31726/TCP 2d4h
kubernetes ClusterIP 10.245.0.1 <none> 443/TCP 3d7h
postgresql ClusterIP None <none> 25060/TCP 19h
But when I try to connect I receive a timeout error of the database, like can't connect to the database.
I have an internet connection in the image.
I find the solution, the problem was the rules of inbound of the database. I must add the IP of Kubernetes.
Thx.

Answer 1

Here is what worked for me:
Define a service , but set clusterIP: None , so no endpooint is created.
And then create an endpoint yourself with the SAME NAME as your service and set the IP and port of your db.
In your example , you have a type in your endpoint: the name of your endpoint is postgresql not postgresSql.
My example:
---
service.yaml
kind: Service
apiVersion: v1
metadata:
name: backend-mobile-db-service
spec:
clusterIP: None
ports:
- port: 5984
---
kind: Endpoints
apiVersion: v1
metadata:
name: backend-mobile-db-service
subsets:
- addresses:
- ip: 192.168.1.50
ports:
- port: 5984
name: backend-mobile-db-service

Answer 2

For better visibility I am placing the answer OP mentioned in question:
I find the solution, the problem was the rules of inbound of the database. I must add the IP of Kubernetes

Answer 3

The service definition should be corrected. Default service type is clusterIP which doesn't work for external database. You need to update the service type as given below
type: ExternalName
also ensure that service name and the endpoint name should match. it is different in your yaml. please check

Answer 4

If I understand correctly, you have your cluster with application on Digital Ocean cloud and your PostgreSQL is outside this cluster.
In your Application Deployment <> application service you have used services with selectors so you didn't need to create Endpoints manually.
In your external database service you have used services without selectors so you had to create Endpoint manually.
As database is external service, using clusterIP: None is pointless as it will try to match pods inside the cluster. I guess you added it as you read in this docs.
Last thing is that in Endpoint you set ip: 206... which is the same as application service LoadBalancer ip?
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
app-service LoadBalancer 10.245.134.137 206........... 6000:31726/TCP 2d4h
subsets:
- addresses:
- ip: 206............
It is only a part of information so I am guessing. However in this part you should provide IP of desired database, not your application Loadbalancer IP.
Now based on scenario you can connect:
Database outside cluster with IP address
Remotely hosted database with URI
Remotely hosted database with URI and port remapping
Detailed information about above scenarios you can find in Kubernetes best practices: mapping external services
Based on your current config I assume you want to use scenario 1.
If this database and cluster are somewhere in cloud you could use internal Database IP. If not you should provide IP of machine where this Database is hosted.
You can also read Kubernetes Access External Services article.
Please let me know if you will still have issue after IP change