Django, Docker, Python - Unable to install Pillow on python-alpine

Question

I have a dockerized django app that I want to put in production. But ever since I added an Imagefield Pillow is required and I struggle to install Pillow in the Docker container.

As far as I understand it, adding the dependencies jpeg-dev ibjpeg & zlib-dev should be enough for django (?). With the configuration below I receive the error:

Error on runserver:

product.Product.image: (fields.E210) Cannot use ImageField because Pillow is not installed.
    HINT: Get Pillow at https://pypi.org/project/Pillow/ or run command "pip install Pillow".
product.Product.thumbnail: (fields.E210) Cannot use ImageField because Pillow is not installed.
    HINT: Get Pillow at https://pypi.org/project/Pillow/ or run command "pip install Pillow".

If I add Pillow to requirements.txt (or putting pip install Pillow in the Dockerfile) I get an even longer error message while trying to build the container.

Without putting pip install Pillow in Dockerfile or requirements.txt - this is my configuration.

Dockerfile:

# pull official base image
FROM python:3.7-alpine

# set environment varibles
ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1

# set work directory
WORKDIR /usr/src/kitschoen-dj

RUN pip install --upgrade pip

# install psycopg2
RUN apk update \
    && apk add --virtual build-deps gcc python3-dev musl-dev \
    && apk add postgresql \
    && apk add postgresql-dev \
    && pip install psycopg2 \
    && apk del build-deps
    && apk add jpeg-dev \
    && apk add libjpeg \
    && apk add zlib-dev

# install dependencies
RUN pip install --upgrade pip
COPY ./requirements.txt /usr/src/kitschoen-dj/requirements.txt
RUN pip install -r requirements.txt

# copy entrypoint.sh
COPY ./entrypoint.sh /usr/src/kitschoen-dj/entrypoint.sh

# copy project
COPY . /usr/src/kitschoen-dj/

# run entrypoint.sh
ENTRYPOINT ["/usr/src/kitschoen-dj/entrypoint.sh"]

Requirements.txt

astroid==2.1.0
certifi==2018.11.29
chardet==3.0.4
Django==2.1.7
django-cors-headers==2.4.0
django-filter==2.1.0
djangorestframework==3.9.1
djangorestframework-simplejwt==3.3
gunicorn==19.9.0
httpie==1.0.2
httpie-jwt-auth==0.3.0
idna==2.8
isort==4.3.4
lazy-object-proxy==1.3.1
Markdown==3.0.1
mccabe==0.6.1
PyJWT==1.7.1
requests==2.21.0
six==1.12.0
urllib3==1.24.1
wrapt==1.11.1

I have been stuck with this for a while. Can someone help?

Answer 1

For anyone who is interested in what worked for me (+ some background on why I ran into this):

Installing Pillow will require several dependencies. As far as I can tell, you need: gcc python3-dev jpeg-dev zlib-dev

To prevent these dependencies from ending up in the final image (keeping the image-size small) you can install some (not all!) of them in a virtual package.

After Pillow is installed successfully you can delete the dependencies that are only required for Pillow's installation.

Dependencies that are only needed during the build are called build dependencies.

So this is the code that worked for me:

RUN apk update \
    && apk add --virtual build-deps gcc python3-dev musl-dev \
    && apk add postgresql \
    && apk add postgresql-dev \
    && pip install psycopg2 \
    && apk add jpeg-dev zlib-dev libjpeg \
    && pip install Pillow \
    && apk del build-deps

(Some of the stuff is not required for Pillow, e. g. postgressql, postgresql-dev). As you can see, I installed my build dependencies in a virtual package called build-deps. AFTER installing the build dependencies, I am installing Pillow. At the end, I am removing the build dependencies.

I think, this is the solution that @LinPy proposed: I just wanted to explain this in a very verbose way to help others.

What is .build-deps for apk add --virtual command?

Answer 2

add this to your Dockerfile:

RUN apk add --no-cache jpeg-dev zlib-dev
RUN apk add --no-cache --virtual .build-deps build-base linux-headers \
    && pip install Pillow

source: Github

Answer 3

I just added these lines to my Dockerfile and it worked

RUN apk add --update --no-cache --virtual .tmp gcc libc-dev linux-headers
RUN apk add --no-cache jpeg-dev zlib-dev
RUN apk del .tmp

---

My Dockerfile (using python:3.8-alpine):

COPY ./requirements.txt /requirements.txt
RUN apk add --update --no-cache --virtual .tmp gcc libc-dev linux-headers
RUN apk add --no-cache jpeg-dev zlib-dev
RUN pip install -r /requirements.txt
RUN apk del .tmp