How can I prevent docker compile a library every time I deploy to bitbucket? Is there any bitbucket pipeline cache? - docker

Question

We have our Flask API in a docker image, we push this docker to a bitbucket repository, then a bitbucket pipeline start deploying.
Everything works as expected, but the compilation of OpenCV is taking in average 15 min.
I would like to know if is there any way to avoid this compilation every time we push to bitbucket. Something like caching.
I have read about cache on bitbucket pipelines but it did not work as I expected.
This is part of my Dockerfile I would like to improve:
RUN mkdir /opt && cd /opt && \
wget -q https://github.com/opencv/opencv/archive/${OPENCV_VERSION}.zip && \
unzip ${OPENCV_VERSION}.zip && \
rm -rf ${OPENCV_VERSION}.zip && \
mkdir -p /opt/opencv-${OPENCV_VERSION}/build && \
cd /opt/opencv-${OPENCV_VERSION}/build && \
CXX=/usr/bin/clang++ CC=/usr/bin/clang cmake \
-D CMAKE_BUILD_TYPE=RELEASE \
-D CMAKE_INSTALL_PREFIX=/usr/local \
-D WITH_FFMPEG=NO \
-D WITH_IPP=NO \
-D WITH_OPENEXR=NO \
-D WITH_TBB=YES \
-D BUILD_EXAMPLES=NO \
-D BUILD_ANDROID_EXAMPLES=NO \
-D INSTALL_PYTHON_EXAMPLES=NO \
-D BUILD_DOCS=NO \
-D BUILD_opencv_python2=NO \
-D BUILD_opencv_python3=ON \
-D ENABLE_PYTHON3=ON \
-D PYTHON3_EXECUTABLE=/usr/bin/python3 \
.. && \
make VERBOSE=1 -j8 && \
make && \
make install && \
rm -rf /opt/opencv-${OPENCV_VERSION}
I expect some solution like just pointing a pre-compiled version of the OpenCV Api.

Answer 1

I have recently faced this problem and agree that cache doesn't seem to work as expected. However without looking at your entire Dockerfile, it's hard to say. ADD's and COPY's will invalidate the cache so i'd suggest you move this section up to the top if you can before adding any files.
A better solution (if there is no pre-compiled version), is to use the concept of a base image which is what I have done to cut my build time down in half. Basically you build a base image flask-api-base which will install all your packages and compile OpenCV and then your actual final image will pull FROM flask-api-base:latest and build your application specific code. Just remember if the base image changes, you may need to wipe your Bitbucket cache.

Answer 2

I'm unfamiliar with OpenCV but assume that, if there is a binary that you can use, that would be the ideal option.
I'm curious as to why this layer (RUN ...) isn't being cached between builds. It appears that you're cleanly separating the make of OpenCV from other statements in your Dockerfile and so, this RUN should generate a distinct layer that's stable and thus reused across builds.
Does this statement occur after earlier e.g. RUN statements that do change? If so, you may want to reorder this statement and place it earlier in the Dockerfile so that this layer becomes constant. See best practices for the Dockerfile statements that generate layers.
Alternatively, you could make a separate image containing OpenCV and then FROM this image in your code builds. You may do this either using distinct Dockerfiles or multi-stage builds. This way, this image containing the OpenCV build would only be built on (your) demand and reused across subsequent builds.

Answer 3

The solution I used was to create my own image, upload it to Docker hub, and create a new one based on that.
So the first docker image should contain all the basic libraries my system uses.
The second has the environmental variables and the api itself.