Connect to PSQL through K8s Ingress - postgresql

Question

I got my own cluster which has a control-plane and worker. i trying to connect to PostgreSQL in the cluster using psql -h <ingress-url> -p 5432 -U postgres -W, but it occur an error:
psql: error: server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
But curl <ingress-url> response like this:
2022-05-27 04:00:50.406 UTC [208] LOG: invalid length of startup packet
That response mean my request have reached to PostgreSQL Server, but why i cannot connect to my PostgreSQL Server?
Here are my resources:
Ingress:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: preflight
labels:
helm.sh/chart: "preflight"
helm.sh/version: "0.1.0"
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /
nginx.ingress.kubernetes.io/ssl-redirect: "false"
spec:
ingressClassName: nginx
rules:
- http:
paths:
- path: /
pathType: Exact
backend:
service:
name: preflight
port:
number: 5432
Deployment:
apiVersion: apps/v1
kind: Deployment
metadata:
name: preflight
labels:
helm.sh/chart: "preflight"
helm.sh/version: "0.1.0"
spec:
replicas: 1
selector:
matchLabels:
helm.sh/chart: "preflight"
helm.sh/version: "0.1.0"
template:
metadata:
labels:
helm.sh/chart: "preflight"
helm.sh/version: "0.1.0"
spec:
containers:
- name: preflight
image: postgres:14
env:
- name: POSTGRES_PASSWORD
valueFrom:
configMapKeyRef:
name: preflight
key: postgresPassword
ports:
- containerPort: 5432
Service:
apiVersion: v1
kind: Service
metadata:
name: preflight
labels:
helm.sh/chart: "preflight"
helm.sh/version: "0.1.0"
spec:
type: ClusterIP
selector:
helm.sh/chart: "preflight"
helm.sh/version: "0.1.0"
ports:
- port: 5432
targetPort: 5432
ConfigMap values is a POSTGRES_PASSWORD=postgres.

Answer 1

Nginx ingress controller is an HTTP proxy. You are trying to route PGSQL traffic over HTTP, and that simply can't work.
What you need to do is expose a TCP service through nginx ingress controller. See this page.
In a nutshell, you need to create a configmap like this:
apiVersion: v1
kind: ConfigMap
metadata:
name: tcp-services
namespace: <namespace where you deployed ingress controller>
data:
5432: "default/preflight:5432"
then ensure your nginx ingress controller starts with the --tcp-services-configmap=tcp-services flag.
Finally, ensure the nginx ingress controller Service (the one with type == LoadBalancer) exposes port 5432:
apiVersion: v1
kind: Service
metadata:
name: ingress-nginx
...
spec:
type: LoadBalancer
ports:
...
- name: pgsql
port: 5432
targetPort: 5432
protocol: TCP
...
Please note that your provider's Load Balancer should support TCP backends (most should do, but worth mentioning).