Use NGINX as database proxy

#watercooler

In our everyday life as dev, we can lose temporary an access to a database from our workstation and it's still available from our Kubernetes cluster. So, in this kind of situation, we can use a proxy to access the database to resolve this network issue.

So today, we will see how to do it with Nginx.

What is NGINX ?

For the ones who didn't already know what is Nginx, it's an opensource software which can be used as web server, load balancer or proxy.

Configurate NGINX

For our case, the Nginx configuration should look like this.

user  nginx;
worker_processes  auto;
error_log /dev/stdout info;
pid        /var/run/nginx.pid;
events {
  worker_connections  1024;  ## Default: 1024
}
http {
  access_log /dev/stdout combined;
  log_format logger-json escape=json '{"source": "nginx", "time": $msec, "resp_body_size": $body_bytes_sent, "host": "$http_host", "address": "$remote_addr", "request_length": $request_length, "method": "$request_method", "uri": "$request_uri", "status": $status,  "user_agent": "$http_user_agent", "resp_time": $request_time, "upstream_addr": "$upstream_addr"}';
    server {
         listen 8080 so_keepalive=on;
        location = /health {
          auth_basic off;
          return 200;
        }
    }
}
stream {
    upstream database {
        server [database endpoint]:[database port];
    }
    server {
        listen [database port] so_keepalive=on;
            proxy_connect_timeout 60s;
            proxy_socket_keepalive on;
            proxy_pass database;
    }
}

Before to use it, some elements must be replaced:

[database endpoint] : The url to access the database
[database port] : The port to access the database

Detail of the configuration

http

This part is only to expose a /health endpoint to use it for the readiness and liveness probes.

stream

This part is the major one in our case.

upstream is here to create a server group. (We don't have multiple instances here, but it makes easier the configuration to read)

The server part will define :

on which port Nginx must listen -> listen
where the traffic will be redirected -> proxy_pass And other configurations like so_keepalive=on and proxy_socket_keepalive on; which are really importante to keep the connection alive.

Deploy on Kubernetes

Once the Nginx configuration is ready, we can now deploy a Nginx instance in our cluster.

Here is a template to create the configmap, deployment & service.

apiVersion: v1
data:
  nginx.conf: "user  nginx;\r\nworker_processes  auto;\r\nerror_log /dev/stdout info;\r\npid
    \ /var/run/nginx.pid;\r\nevents {\r\n  worker_connections  1024;  ## Default:
    1024\r\n}\r\n\r\nhttp {\r\n  access_log /dev/stdout combined;\r\n  log_format
    logger-json escape=json '{\"source\": \"nginx\", \"time\": $msec, \"resp_body_size\":
    $body_bytes_sent, \"host\": \"$http_host\", \"address\": \"$remote_addr\", \"request_length\":
    $request_length, \"method\": \"$request_method\", \"uri\": \"$request_uri\", \"status\":
    $status,  \"user_agent\": \"$http_user_agent\", \"resp_time\": $request_time,
    \"upstream_addr\": \"$upstream_addr\"}';\r\n\r\n\r\n    server {\r\n         listen
    8080 so_keepalive=on;\r\n\r\n        location = /health {\r\n          auth_basic
    off;\r\n          return 200;\r\n        }\r\n    }\r\n}\r\nstream {\r\n    upstream
    postgres {\r\n        server database:port;\r\n
    \ }\r\n\r\n    server {\r\n        listen port so_keepalive=on;\r\n            proxy_connect_timeout
    60s;\r\n            proxy_socket_keepalive on;\r\n            proxy_pass postgres;\r\n
    \ }\r\n}"
kind: ConfigMap
metadata:
  name: nginx-config
---
apiVersion: v1
kind: Service
metadata:
  name: nginx
spec:
  ports:
    - port: 8080
      protocol: TCP
      targetPort: 8080
      name: http
    - port: port
      protocol: TCP
      targetPort: port
      name: database
  selector:
    app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
      name: nginx
    spec:
      containers:
        - args:
            - nginx
            - -g
            - daemon off;
            - -c
            - /nginx/etc/config/nginx.conf
          image: nginx:1.23.3
          imagePullPolicy: IfNotPresent
          livenessProbe:
            httpGet:
              path: /health
              port: nginx
              scheme: HTTP
            initialDelaySeconds: 10
          name: nginx
          ports:
            - containerPort: 8080
              name: nginx
              protocol: TCP
            - containerPort: port
              name: database
              protocol: TCP
          readinessProbe:
            httpGet:
              path: /health
              port: nginx
              scheme: HTTP
            initialDelaySeconds: 10
          resources:
            limits:
              memory: 200Mi
            requests:
              cpu: 50m
              memory: 200Mi
          volumeMounts:
            - mountPath: /nginx/etc/config
              name: nginx-config-volume
      volumes:
        - configMap:
            name: nginx-config
          name: nginx-config-volume

Before to use it, be sure to put the correct informations in the confimap and to define correctly the port in the service & deployment definition!

Usage

Once deployed, you can expose the deployment with an Ingress or simply do a port forward from your workstation to be able to do locally all the manipulations you want!

I hope it will help you! 🍺