We have a python project, and the current docker build takes 350s. Here is the current Dockerfile FROM python:3.9 RUN apt-get update && \ apt-get install -y python2.7 WORKDIR /var/app COPY . . RUN pip install ENTRYPOINT ["python3", "/var/app/src/main.py"] This took 350s on every docker build There was obvious room for improvement here so, I changed it to this FROM python:3.9 RUN apt-get update && \ apt-get install -y python2.7 WORKDIR /var/app COPY requirements.txt . RUN pip install -r requirements.txt COPY . . RUN pip install ENTRYPOINT ["python3", "/var/app/src/main.py"] This brings subsequent build down to 1s I also came across the following after a bit of searching, FROM python:3.9 RUN apt-get update && \ apt-get install -y python2.7 WORKDIR /var/app COPY requirements.txt . RUN --mount=type=cache,target=/root/.cache/pip pip install -r requirements.txt COPY . . RUN pip install ENTRYPOINT ["python3", "/var/app/src/main.py"] This takes a bit longer around 80s but better than the 1st one What I don't understand is what are the caveats with #2 (to be safe). When should I use #3 I have no experience with pip/docker fyi With #2, as a side effect of docker caching layers, if any of my dependencies dependency version changes, because of using range operators, then I still won't rebuild anything. Is that what #3 is trying to solve? i.e. it will reuse cache as much as it can but also makes sure to update anything necessary If not, I have no idea what's going on with #3. Is the /root/.cache/pip a pip specific directory or it can be anything? Continue reading...
