Update README.md with docker using celery and redis

deployment_tools/docker/README.md

@@ -64,3 +64,119 @@ You'll still need to set the dashboard password:
 - Using a modern IDE, you can also directly edit the files inside the containers - and even debug them!
 
 
+## Combining py4web with Celery and Redis
+
+Celery can be used for handling long running background tasks. 
+Celery uses Redis as broker. Redis will be run in a seperate container. 
+
+At the end of the docker-compose file add:
+
+    redis:
+        restart: always
+        image: redis
+        ports:
+          - "6379:6379"
+
+In the app (based on _scaffold) settings.py:
+
+    #Celery settings
+    USE_CELERY = True
+    CELERY_BROKER = "redis://redis:6379/0"
+    CELERY_BACKEND = "redis://redis:6379/0"
+
+In common.py:
+
+    # #######################################################
+    # Optionally configure celery
+    # #######################################################
+    if settings.USE_CELERY:
+        from celery import Celery
+
+        # to use "from .common import scheduler" and then use it according
+        # to celery docs, examples in tasks.py
+        scheduler = Celery(
+            "apps.%s.tasks" % settings.APP_NAME, broker=settings.CELERY_BROKER,  backend=settings.CELERY_BACKEND)      
+        scheduler.conf.broker_connection_retry_on_startup = True
+
+In the docker file use entrypoint.sh to get the scheduler going and start py4web.
+
+    entrypoint.sh:
+
+    #!/bin/bash
+    . /home/py4web/.venv/bin/activate
+    exec .venv/bin/celery -A apps.myapp.tasks beat &
+    exec .venv/bin/celery -A apps.myapp.tasks worker --loglevel=info &
+    exec py4web run --password_file password.txt --host 0.0.0.0 --port 8000 apps
+
+complete Dockerfile:
+
+    FROM ubuntu:latest
+
+    ARG user=py4web
+    ENV PY4WEB_ROOT=/home/$user
+
+    RUN apt update && \
+        apt install -y git locales locales-all python3.12 python3-pip python3.12-venv memcached && \
+        service memcached restart && \
+        groupadd -r $user && \
+        useradd -m -r -g $user $user && \
+        python3 -m venv  $PY4WEB_ROOT/.venv && \
+        . $PY4WEB_ROOT/.venv/bin/activate && \
+        python3 -m pip install -U py4web  psycopg2-binary && \
+        python3 -m pip install -U "celery[redis]"
+
+    ENV LC_ALL en_US.UTF-8
+    ENV LANG en_US.UTF-8
+    ENV LANGUAGE en_US.UTF-8  
+
+    USER $user
+
+    RUN . $PY4WEB_ROOT/.venv/bin/activate && \
+        cd $PY4WEB_ROOT/ && py4web setup --yes apps
+    # use   ./venv/bin/py4web set_password
+    COPY password.txt $PY4WEB_ROOT/.
+
+    EXPOSE 8000
+
+    WORKDIR $PY4WEB_ROOT/
+    COPY entrypoint.sh /usr/local/bin/
+    ENTRYPOINT [ "entrypoint.sh" ]
+
+docker-compose.yml
+
+    services:
+
+      web:
+        build: .
+        ports:
+          - "8000:8000"
+        environment:
+         - PYDAL_URI=postgres://foo:bar@postgres:5432/baz
+         - PYDAL_URI2=mysql://root:secret@localhost/ursadina_gtd
+        volumes:
+         - ./apps:/home/py4web/apps
+        stdin_open: true
+        tty: true
+        depends_on:
+          - postgres
+          - redis
+
+      postgres:
+        restart: always
+        image: postgres
+        environment:
+          - POSTGRES_USER=foo
+          - POSTGRES_PASSWORD=bar
+          - POSTGRES_DB=baz
+          - POSTGRES_PORT=5432
+        ports:
+          - "5432:5432"
+        volumes:
+           - ./data/postgres:/var/lib/postgresql/data
+      redis:
+        restart: always
+        image: redis
+        ports:
+          - "6379:6379"
+
+