Change Docker image to multi-stage build for Django

{{cookiecutter.project_slug}}/compose/local/django/Dockerfile

@@ -1,22 +1,57 @@
-FROM python:3.8-slim-buster
+ARG PYTHON_VERSION=3.8-slim-buster
+
+# define an alias for the specfic python version used in this file.
+FROM python:${PYTHON_VERSION} as python
+
+# Python build stage
+FROM python as python-build-stage
+
+ARG BUILD_ENVIRONMENT=local
+
+# Install apt packages
+RUN apt-get update && apt-get install --no-install-recommends -y \
+  # dependencies for building Python packages
+  build-essential \
+  # psycopg2 dependencies
+  libpq-dev
+
+# Requirements are installed here to ensure they will be cached.
+COPY ./requirements .
+
+# Create Python Dependency and Sub-Dependency Wheels.
+RUN pip wheel --wheel-dir /usr/src/app/wheels  \
+  -r ${BUILD_ENVIRONMENT}.txt
+
+
+# Python 'run' stage
+FROM python as python-run-stage
+
+ARG BUILD_ENVIRONMENT=local
+ARG APP_HOME=/app
 
 ENV PYTHONUNBUFFERED 1
 ENV PYTHONDONTWRITEBYTECODE 1
+ENV BUILD_ENV ${BUILD_ENVIRONMENT}
 
-RUN apt-get update \
-  # dependencies for building Python packages
-  && apt-get install -y build-essential \
+WORKDIR ${APP_HOME}
+
+# Install required system dependencies
+RUN apt-get update && apt-get install --no-install-recommends -y \
   # psycopg2 dependencies
-  && apt-get install -y libpq-dev \
+  libpq-dev \
   # Translations dependencies
-  && apt-get install -y gettext \
+  gettext \
   # cleaning up unused files
   && apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false \
   && rm -rf /var/lib/apt/lists/*
 
-# Requirements are installed here to ensure they will be cached.
-COPY ./requirements /requirements
-RUN pip install -r /requirements/local.txt
+# All absolute dir copies ignore workdir instruction. All relative dir copies are wrt to the workdir instruction
+# copy python dependency wheels from python-build-stage
+COPY --from=python-build-stage /usr/src/app/wheels  /wheels/
+
+# use wheels to install python dependencies
+RUN pip install --no-cache-dir --no-index --find-links=/wheels/ /wheels/* \
+	&& rm -rf /wheels/
 
 COPY ./compose/production/django/entrypoint /entrypoint
 RUN sed -i 's/\r$//g' /entrypoint
@@ -25,6 +60,7 @@ RUN chmod +x /entrypoint
 COPY ./compose/local/django/start /start
 RUN sed -i 's/\r$//g' /start
 RUN chmod +x /start
+
 {% if cookiecutter.use_celery == "y" %}
 COPY ./compose/local/django/celery/worker/start /start-celeryworker
 RUN sed -i 's/\r$//g' /start-celeryworker
@@ -38,6 +74,8 @@ COPY ./compose/local/django/celery/flower/start /start-flower
 RUN sed -i 's/\r$//g' /start-flower
 RUN chmod +x /start-flower
 {% endif %}
-WORKDIR /app
 
-ENTRYPOINT ["/entrypoint"]
+# copy application code to WORKDIR
+COPY . ${APP_HOME}
+
+ENTRYPOINT ["/entrypoint"]

{{cookiecutter.project_slug}}/compose/production/django/Dockerfile

@@ -1,36 +1,75 @@
 {% if cookiecutter.js_task_runner == 'Gulp' -%}
 FROM node:10-stretch-slim as client-builder
 
-WORKDIR /app
-COPY ./package.json /app
+ARG APP_HOME=/app
+WORKDIR ${APP_HOME}
+
+COPY ./package.json ${APP_HOME}
 RUN npm install && npm cache clean --force
-COPY . /app
+COPY . ${APP_HOME}
 RUN npm run build
 
-# Python build stage
 {%- endif %}
-FROM python:3.8-slim-buster
 
-ENV PYTHONUNBUFFERED 1
+ARG PYTHON_VERSION=3.8-slim-buster
+
+# define an alias for the specfic python version used in this file.
+FROM python:${PYTHON_VERSION} as python
 
-RUN apt-get update \
+# Python build stage
+FROM python as python-build-stage
+
+ARG BUILD_ENVIRONMENT=production
+
+# Install apt packages
+RUN apt-get update && apt-get install --no-install-recommends -y \
   # dependencies for building Python packages
-  && apt-get install -y build-essential \
+  build-essential \
   # psycopg2 dependencies
-  && apt-get install -y libpq-dev \
+  libpq-dev
+
+# Requirements are installed here to ensure they will be cached.
+COPY ./requirements .
+
+# Create Python Dependency and Sub-Dependency Wheels.
+RUN pip wheel --wheel-dir /usr/src/app/wheels  \
+  -r ${BUILD_ENVIRONMENT}.txt
+
+
+# Python 'run' stage
+FROM python as python-run-stage
+
+ARG BUILD_ENVIRONMENT=production
+ARG APP_HOME=/app
+
+ENV PYTHONUNBUFFERED 1
+ENV PYTHONDONTWRITEBYTECODE 1
+ENV BUILD_ENV ${BUILD_ENVIRONMENT}
+
+WORKDIR ${APP_HOME}
+
+RUN addgroup --system django \
+    && adduser --system --ingroup django django
+
+
+# Install required system dependencies
+RUN apt-get update && apt-get install --no-install-recommends -y \
+  # psycopg2 dependencies
+  libpq-dev \
   # Translations dependencies
-  && apt-get install -y gettext \
+  gettext \
   # cleaning up unused files
   && apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false \
   && rm -rf /var/lib/apt/lists/*
 
-RUN addgroup --system django \
-    && adduser --system --ingroup django django
+# All absolute dir copies ignore workdir instruction. All relative dir copies are wrt to the workdir instruction
+# copy python dependency wheels from python-build-stage
+COPY --from=python-build-stage /usr/src/app/wheels  /wheels/
+
+# use wheels to install python dependencies
+RUN pip install --no-cache-dir --no-index --find-links=/wheels/ /wheels/* \
+	&& rm -rf /wheels/
 
-# Requirements are installed here to ensure they will be cached.
-COPY ./requirements /requirements
-RUN pip install --no-cache-dir -r /requirements/production.txt \
-    && rm -rf /requirements
 
 COPY --chown=django:django ./compose/production/django/entrypoint /entrypoint
 RUN sed -i 's/\r$//g' /entrypoint
@@ -58,14 +97,17 @@ RUN sed -i 's/\r$//g' /start-flower
 RUN chmod +x /start-flower
 {%- endif %}
 
+
+# copy application code to WORKDIR
 {%- if cookiecutter.js_task_runner == 'Gulp' %}
-COPY --from=client-builder --chown=django:django /app /app
+COPY --from=client-builder --chown=django:django ${APP_HOME} ${APP_HOME}
 {% else %}
-COPY --chown=django:django . /app
+COPY --chown=django:django . ${APP_HOME}
 {%- endif %}
 
-USER django
+# make django owner of the WORKDIR directory as well.
+RUN chown django:django ${APP_HOME}
 
-WORKDIR /app
+USER django
 
-ENTRYPOINT ["/entrypoint"]
+ENTRYPOINT ["/entrypoint"]