use --no-cache-dir flag to pip in dockerfiles to save space

using the "--no-cache-dir" flag in pip install, make sure downloaded packages
by pip don't cache on the system. This is a best practice that makes sure
to fetch from a repo instead of using a local cached one. Further, in the case
of Docker Containers, by restricting caching, we can reduce image size.
In terms of stats, it depends upon the number of python packages
multiplied by their respective size. e.g for heavy packages with a lot
of dependencies it reduces a lot by don't cache pip packages.

Further, more detailed information can be found at

https://medium.com/sciforce/strategies-of-docker-images-optimization-2ca9cc5719b6

Signed-off-by: Pratik Raj <[email protected]>

Author: rajpratik71

Dockerfile

@@ -1,6 +1,6 @@
 FROM fedora:33
 RUN dnf install -y git podman buildah python3-libselinux python3-pip
-RUN pip3 install ansible==2.10.5 jmespath
+RUN pip3 install --no-cache-dir ansible==2.10.5 jmespath
 RUN mkdir -p /playbooks
 COPY roles/ /playbooks/roles/
 COPY filter_plugins/ /playbooks/filter_plugins/

Dockerfiles/ci/Dockerfile

@@ -13,6 +13,6 @@ RUN export ARCH=$(case $(arch) in x86_64) echo -n amd64 ;; aarch64) echo -n arm6
     mkdir /project/output && \
     dnf install --setopt=install_weak_deps=False -y git-core ansible python3-pip mlocate jq skopeo && \
     dnf clean all && \
-    pip3 install operator-courier
+    pip3 install --no-cache-dir operator-courier
 ADD ./run_tests.py /run_tests.py
 CMD ["/run_tests.py"]

upstream/roles/install_iib/templates/Dockerfile-workers.j2

@@ -75,6 +75,6 @@ RUN sed -i -e 's|^#mount_program|mount_program|g' /etc/containers/storage.conf
 COPY docker/libpod.conf /usr/share/containers/libpod.conf
 
 COPY . .
-RUN pip3 install -r requirements.txt --no-deps --require-hashes
-RUN pip3 install . --no-deps
+RUN pip3 install --no-cache-dir -r requirements.txt --no-deps --require-hashes && \
+    pip3 install --no-cache-dir . --no-deps
 CMD ["/bin/celery-3", "-A", "iib.workers.tasks", "worker", "--loglevel=info"]