Add HAproxy example

Author: valentinab25

docs/install/containers/examples/haproxy-plone-zeo.md

@@ -0,0 +1,76 @@
+---
+html_meta:
+  "description": "Simple Plone 6 setup with scalable backend and data being persisted in a Zeo volume."
+  "property=og:description": "Simple Plone 6 setup with scalable backend and data being persisted in a Zeo volume."
+  "property=og:title": "HAproxy, Backend, ZEO container example"
+  "keywords": "Plone 6, Container, Docker, HAproxy, Zeo"
+---
+
+# Haproxy, Backend, ZEO container example
+
+Very simple setup with only one or more backend instances accessing a ZEO server and data being persisted in a Docker volume.
+
+## Setup
+
+Create a directory for your project, and inside it create a `docker-compose.yml` file that starts your Plone instance and the ZEO instance with volume mounts for data persistence.
+HAProxy is used for load balancing in this example.
+
+```yaml
+version: "3"
+services:
+
+  lb:
+    image: plone/plone-haproxy
+    depends_on:
+    - backend
+    ports:
+    - "8080:8080"
+    - "1936:1936"
+    environment:
+      FRONTEND_PORT: "8080"
+      BACKENDS: "backend"
+      BACKENDS_PORT: "8080"
+      DNS_ENABLED: "True"
+      HTTPCHK: "GET /"
+      INTER: "5s"
+      LOG_LEVEL: "info"
+
+  backend:
+    image: plone/plone-backend:6.0.0a4
+    restart: always
+    environment:
+      ZEO_ADDRESS: zeo:8100
+    ports:
+    - "8080"
+    depends_on:
+      - zeo
+
+  zeo:
+    image: plone/plone-zeo:latest
+    restart: always
+    volumes:
+      - data:/data
+    ports:
+    - "8100"
+
+volumes:
+  data: {}
+```
+
+## Build the project with multiple backends
+
+Run `docker-compose up -d --scale backend=4` from your project directory.
+
+## Access Plone via Browser
+
+Point your browser at `http://localhost:8080`, using the username and password combination of `admin` and `admin`, and you should see the default Plone site creation page.
+
+## Access HAProxy Stats Page via Browser
+
+Point your browser at `http://localhost:1936`, using the username and password combination of `admin` and `admin`, and you should see HAProxy statistics for your Plone cluster.
+
+## Shutdown and cleanup
+
+The command `docker-compose down` removes the containers and default network, but preserves the Plone database.
+
+The command `docker-compose down --volumes` removes the containers, default network, and the Plone database.