adding dockerfile

Author: Y4rd13

Dockerfile

@@ -0,0 +1,47 @@
+# The dockerfile uses multi-stage builds to build the application
+# and then copy the build artifacts to the final image. This helps for the layer optimization.
+# https://docs.docker.com/develop/develop-images/multistage-build/
+#
+# Environment replacement
+#   - "PYTHONDONTWRITEBYTECODE 1": Python won’t try to write .pyc files on the import of source modules
+#     It make sense in a container, since the process runs just once.
+#   
+#   - "PYTHONUNBUFFERED 1": Force the stdout and stderr streams to be unbuffered. This option has no effect on the stdin stream.
+#   - "PIP_NO_CACHE_DIR 1": Disable pip cache, used to shrink the image size by disabling the cache.
+#   
+#   - PATH: defining virtual enviroment in /opt, since is used to reserved for the installation of add-on application software packages.
+#     This can help with with minimizing docker image size when doing multi-staged builds.
+#   
+# WORKDIR: https://docs.docker.com/engine/reference/builder/
+#   - WORKDIR /app: set the working directory for any RUN, CMD, ENTRYPOINT, COPY and ADD instructions that follow it in the Dockerfile.
+#   - we don't even need to run mkdir /app since WORKDIR will make it for us.
+#   - good practice because we can set a directory as the main directory
+# "COPY . .": the contents of the build context directory will be copied to the /myapp dir inside your docker image.
+# (COPY <src: "relative to the build context directory"> (TO) <dest: "relative to the WORKDIR directory">)
+
+### build stage ###
+FROM python:3.9 AS builder
+
+WORKDIR /app
+
+ENV PYTHONDONTWRITEBYTECODE 1
+ENV PYTHONUNBUFFERED 1
+ENV PIP_NO_CACHE_DIR 1
+ENV PATH="/opt/venv/bin:$PATH"
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends gcc && \
+    python -m venv /opt/venv
+
+COPY requirements.txt .
+RUN pip install -r requirements.txt
+
+### final stage ###
+FROM python:3.9-slim
+
+WORKDIR /app
+
+ENV PATH="/opt/venv/bin:$PATH"
+
+COPY --from=builder /opt/venv /opt/venv
+COPY . .