Docker pip dependencies installation error

Question

I'm trying to build a Docker image for a Flask app I wrote, but I'm getting a pip related error when it's installing the build dependencies as you can see from the log below.

I'm using pipenv for dependency management, and I'm able to get the app running locally without any error using pipenv run python3 run.py

It seems it's not able to install bcrypt, but I can't figure out why.

Dockerfile:

FROM alpine:3.8

RUN apk add --no-cache python3-dev && pip3 install --upgrade pip
WORKDIR /app
COPY . /app
RUN pip3 --no-cache-dir install -r requirements.txt
EXPOSE 5000
ENTRYPOINT ["python3"]
CMD ["run.py"]

requirements.txt (generated with pipenv shell; pip freeze > requirements.txt)

bcrypt==3.1.6
blinker==1.4
cffi==1.11.5
Click==7.0
Flask==1.0.2
Flask-Bcrypt==0.7.1
Flask-Login==0.4.1
Flask-Mail==0.9.1
Flask-SQLAlchemy==2.3.2
Flask-WTF==0.14.2
itsdangerous==1.1.0
Jinja2==2.10
MarkupSafe==1.1.0
Pillow==5.4.1
pycparser==2.19
six==1.12.0
SQLAlchemy==1.2.17
Werkzeug==0.14.1
WTForms==2.2.1

Docker build image process log:

$ docker build -t flaskapp:latest .
Sending build context to Docker daemon   2.16MB
Step 1/8 : FROM alpine:3.8
 ---> 3f53bb00af94
Step 2/8 : RUN apk add --no-cache python3-dev && pip3 install --upgrade pip
 ---> Using cache
 ---> 3856c6d59bbe
Step 3/8 : WORKDIR /app
 ---> Using cache
 ---> 54ed0e7464e4
Step 4/8 : COPY . /app
 ---> Using cache
 ---> 9e045f4ce91c
Step 5/8 : RUN pip3 --no-cache-dir install -r requirements.txt
 ---> Running in 25909f37b071
Collecting bcrypt==3.1.6 (from -r requirements.txt (line 1))
  Downloading https://files.pythonhosted.org/packages/ce/3a/3d540b9f5ee8d92ce757eebacf167b9deedb8e30aedec69a2a072b2399bb/bcrypt-3.1.6.tar.gz (42kB)
  Installing build dependencies: started
  Installing build dependencies: finished with status 'error'
  Complete output from command /usr/bin/python3.6 /usr/lib/python3.6/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-9iojppec/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- setuptools wheel "cffi>=1.1; python_implementation != 'PyPy'":
  Collecting setuptools
    Downloading https://files.pythonhosted.org/packages/bf/ae/a23db1762646069742cc21393833577d3fa438eecaa59d11fb04fa57fcd5/setuptools-40.7.1-py2.py3-none-any.whl (574kB)
  Collecting wheel
    Downloading https://files.pythonhosted.org/packages/ff/47/1dfa4795e24fd6f93d5d58602dd716c3f101cfd5a77cd9acbe519b44a0a9/wheel-0.32.3-py2.py3-none-any.whl
  Collecting cffi>=1.1
    Downloading https://files.pythonhosted.org/packages/e7/a7/4cd50e57cc6f436f1cc3a7e8fa700ff9b8b4d471620629074913e3735fb2/cffi-1.11.5.tar.gz (438kB)
      Complete output from command python setup.py egg_info:
      Package libffi was not found in the pkg-config search path.
      Perhaps you should add the directory containing `libffi.pc'
      to the PKG_CONFIG_PATH environment variable
      Package 'libffi', required by 'virtual:world', not found
      Package libffi was not found in the pkg-config search path.
      Perhaps you should add the directory containing `libffi.pc'
      to the PKG_CONFIG_PATH environment variable
      Package 'libffi', required by 'virtual:world', not found
      Package libffi was not found in the pkg-config search path.
      Perhaps you should add the directory containing `libffi.pc'
      to the PKG_CONFIG_PATH environment variable
      Package 'libffi', required by 'virtual:world', not found
      Package libffi was not found in the pkg-config search path.
      Perhaps you should add the directory containing `libffi.pc'
      to the PKG_CONFIG_PATH environment variable
      Package 'libffi', required by 'virtual:world', not found
      Package libffi was not found in the pkg-config search path.
      Perhaps you should add the directory containing `libffi.pc'
      to the PKG_CONFIG_PATH environment variable
      Package 'libffi', required by 'virtual:world', not found

          No working compiler found, or bogus compiler options passed to
          the compiler from Python's standard "distutils" module.  See
          the error messages above.  Likely, the problem is not related
          to CFFI but generic to the setup.py of any Python package that
          tries to compile C code.  (Hints: on OS/X 10.8, for errors about
          -mno-fused-madd see http://stackoverflow.com/questions/22313407/
          Otherwise, see https://wiki.python.org/moin/CompLangPython or

EDIT:

After changing the RUN command in Dockerfile to:

RUN apk add --no-cache python3-dev openssl-dev libffi-dev gcc musl-dev && pip3 install --upgrade pip

I now get this error (relevant part posted):

...
Collecting SQLAlchemy==1.2.17 (from -r requirements.txt (line 17))
Downloading https://files.pythonhosted.org/packages/c6/52/73d1c92944cd294a5b165097038418abb6a235f5956d43d06f97254f73bf/SQLAlchemy-1.2.17.tar.gz (5.7MB)
Collecting Werkzeug==0.14.1 (from -r requirements.txt (line 18))
Downloading https://files.pythonhosted.org/packages/20/c4/12e3e56473e52375aa29c4764e70d1b8f3efa6682bef8d0aae04fe335243/Werkzeug-0.14.1-py2.py3-none-any.whl (322kB)
Collecting WTForms==2.2.1 (from -r requirements.txt (line 19))
Downloading https://files.pythonhosted.org/packages/9f/c8/dac5dce9908df1d9d48ec0e26e2a250839fa36ea2c602cc4f85ccfeb5c65/WTForms-2.2.1-py2.py3-none-any.whl (166kB)
Exception:
Traceback (most recent call last):
File "/usr/lib/python3.6/site-packages/pip/_internal/cli/base_command.py", line 176, in main
status = self.run(options, args)
File "/usr/lib/python3.6/site-packages/pip/_internal/commands/install.py", line 346, in run
session=session, autobuilding=True
File "/usr/lib/python3.6/site-packages/pip/_internal/wheel.py", line 886, in build
assert have_directory_for_build
AssertionError
The command '/bin/sh -c pip3 --no-cache-dir install -r requirements.txt' returned a non-zero code: 2

EDIT2:

It seems it's an Alpine Linux known issue. More info here: have_directory_for_build AssertionError when installing with --no-cache-dir (19.0.1)

Answer 1

The problem is that cffi requires a compiler and development libraries to be available on install.

A simple way to get around this is by simply installing the required packages as part of the docker build process.

RUN apk add --no-cache python3-dev openssl-dev libffi-dev gcc && pip3 install --upgrade pip

This might not be the best long term solution and something like multi-stage builds might be better long term.