How to use Skaffold with kubernetes volumes?

Question

I have an python application whose docker build takes about 15-20 minutes. Here is how my Dockerfile looks like more or less

FROM ubuntu:18.04
...
COPY . /usr/local/app
RUN pip install -r /usr/local/app/requirements.txt
...
CMD ...

Now if I use skaffold, any code change triggers a rebuild and it is going to do a reinstall of all requirements(as from the COPY step everything else is going to be rebuild) regardless of whether they were already installed. iIn docker-compose this issue would be solved using volumes. In kubernetes, if we use volumes in the following way:

apiVersion: v1
kind: Pod
metadata:
name: test
spec:
containers:
- image: test:test
name: test-container
volumeMounts:
- mountPath: /usr/local/venv # this is the directory of the 
# virtualenv of python
    name: test-volume
volumes:
- name: test-volume
  awsElasticBlockStore:
    volumeID: <volume-id>
    fsType: ext4

will this extra requirements build be resolved with skaffold?

Answer 1

I can't speak for skaffold specifically but the container image build can be improved. If there is layer caching available then only reinstall the dependencies when your requirements.txt changes. This is documented in the "ADD or COPY" Best Practices.

FROM ubuntu:18.04
...
COPY requirements.txt /usr/local/app/
RUN pip install -r /usr/local/app/requirements.txt
COPY . /usr/local/app
...
CMD ...

You may need to trigger updates some times if the module versions are loosely defined and say you want a new patch version. I've found requirements should be specific so versions don't slide underneath your application without your knowledge/testing.

Kaniko in-cluster builds

For kaniko builds to make use of a cache in a cluster where there is no persistent storage by default, kaniko needs either a persistent volume mounted (--cache-dir) or a container image repo (--cache-repo) with the layers available.