Merge pull request #839 from readthedocs/davidfischer/docker-pip-cache

Use a docker pip cache

docker-compose/django/Dockerfile

@@ -29,17 +29,18 @@ RUN apt-get -y install \
         lsb-release
 
 # Requirements are installed here to ensure they will be cached.
+# https://docs.docker.com/build/cache/#use-the-dedicated-run-cache
 COPY ./requirements /requirements
 RUN pip install --upgrade pip
-RUN pip install -r /requirements/development.txt
-RUN pip install -r /requirements/production.txt
+RUN --mount=type=cache,target=/root/.cache/pip pip install -r /requirements/development.txt
+RUN --mount=type=cache,target=/root/.cache/pip pip install -r /requirements/production.txt
 
 # Comment this if you don't need the page/topic analyzer.
 # The analyzer is used to target ads better based on page content.
 # Its requirements are huge and include PyTorch and other ML tools.
 # If not needed, make sure to set `ADSERVER_ANALYZER_BACKEND=` (empty string)
 # in your environment file `./envs/local/django`.
-RUN pip install -r /requirements/analyzer.txt
+RUN --mount=type=cache,target=/root/.cache/pip pip install -r /requirements/analyzer.txt
 
 COPY ./docker-compose/django/start /start
 RUN chmod +x /start