Use multi-stage docker build

Author: AllenAnthes

docker/Dockerfile

@@ -1,23 +1,45 @@
-FROM python:3.7-slim
+FROM python:3.7-alpine AS base
 
-# Create and set the working directory to /pybot
-WORKDIR /pybot
+FROM base as builder
+
+ENV PIP_DISABLE_PIP_VERSION_CHECK on
+ENV PYTHONDONTWRITEBYTECODE 1
+ENV PYTHONUNBUFFERED 1
+
+RUN apk update && \
+    apk add --no-cache build-base musl-dev python3-dev
+
+RUN python -m venv /opt/venv
+# Make sure we use the virtualenv:
+ENV PATH="/opt/venv/bin:$PATH"
 
-# Copy the pipfile into the pybot directory
 COPY poetry.lock pyproject.toml ./
 
-# Install anything missing from the slim image, install dependnecies, remove anything only needed for building
-# This is run as one line so docker caches it as a single layer.
-RUN apt-get update \
-    && apt-get install -y gcc  \
-    && rm -rf /var/lib/apt/lists/* \
-    && pip install poetry \
-    && poetry config settings.virtualenvs.create false \
-    && poetry install \
-    && apt-get purge -y --auto-remove gcc
-
-# Copy the rest of our app into the container
-COPY . /pybot
-
-# Run the pybot module
-ENTRYPOINT ["python3", "-m", "pybot"]
+RUN pip install poetry && \
+    poetry config settings.virtualenvs.create false && \
+    poetry install --no-dev --no-interaction --no-ansi
+
+# The `built-image` stage is the base for all remaining images
+# Pulls all of the built dependencies from the builder stage
+FROM base as built-image
+ENV PIP_DISABLE_PIP_VERSION_CHECK on
+ENV PYTHONDONTWRITEBYTECODE 1
+ENV PYTHONUNBUFFERED 1
+
+# copy installed deps from builder image
+COPY --from=builder /opt/venv /opt/venv
+
+# Make sure we use the virtualenv
+ENV PATH="/opt/venv/bin:$PATH"
+
+# The `app` stage is used as the base for images that don't
+# need the development dependencies
+FROM built-image as app
+
+COPY . /src
+WORKDIR /src
+
+# The `Prod` stage creates an image that will run the application using a
+# production webserver and the `environments/production.py` configuration
+FROM app As Prod
+ENTRYPOINT ["python3", "-m", "pybot"]