`pip install cyrptography ` not able to install on python3.7-alpine docker - docker

Question

I'm trying to install crypotography using the below dockerfile for alpine3.7 python base.
However, I'm getting error like this:
#7 17.27 Failed to build cryptography cffi
#7 17.37 Installing collected packages: pycparser, six, idna, cffi, asn1crypto, pymysql, cryptography
#7 17.68 Running setup.py install for cffi: started
#7 18.04 Running setup.py install for cffi: finished with status 'error'
#7 18.04 ERROR: Command errored out with exit status 1:
#7 18.04 command: /usr/local/bin/python -u -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-twxf8fj_/cffi_1f087e9b9e8c4af8b4e6bf3deb3a5bf9/setup.py'"'"'; __file__='"'"'/tmp/pip-install-twxf8fj_/cffi_1f087e9b9e8c4af8b4e6bf3deb3a5bf9/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-j8mkceyt/install-record.txt --single-version-externally-managed --compile --install-headers /usr/local/include/python3.7m/cffi
#7 18.04 cwd: /tmp/pip-install-twxf8fj_/cffi_1f087e9b9e8c4af8b4e6bf3deb3a5bf9/
#7 18.04 Complete output (48 lines):
#7 18.04 unable to execute 'gcc': No such file or directory
#7 18.04 unable to execute 'gcc': No such file or directory
As per cryptography document I'm installing all necessary packages but still it's throwing me the same error.
Dockerfile:
FROM python:3.7-alpine
WORKDIR /project
RUN apk add --no-cache --virtual gcc musl-dev python3-dev libffi-dev openssl-dev cargo mariadb-dev
RUN pip install pymysql cryptography
Can you anyone point me what is i'm doing wrong?

Answer 1

-t, --virtual NAME Instead of adding all the packages to 'world', create a new
virtual package with the listed dependencies and add that
to 'world'; the actions of the command are easily reverted
by deleting the virtual package
What that means is when you install packages, those packages are not added to global packages. And this change can be easily reverted. So if I need gcc to compile a program, but once the program is compiled I no more need gcc.
I can install gcc, and other required packages in a virtual package and all of its dependencies and everything can be removed this virtual package name. Below is an example usage:
apk add --virtual .dep gcc
apk del .dep
So, for you, in apk add --no-cache --virtual gcc, the gcc was wrongly treat as virtual package name, which means you in fact did not install gcc.
To fix this, try to add a virtual package name before all packages as next:
/ # apk add --no-cache --virtual .dep gcc
fetch https://mirrors.ustc.edu.cn/alpine/v3.14/main/x86_64/APKINDEX.tar.gz
fetch https://mirrors.ustc.edu.cn/alpine/v3.14/community/x86_64/APKINDEX.tar.gz
(1/12) Installing libgcc (10.3.1_git20210424-r2)
(2/12) Installing libstdc++ (10.3.1_git20210424-r2)
(3/12) Installing binutils (2.35.2-r2)
(4/12) Installing libgomp (10.3.1_git20210424-r2)
(5/12) Installing libatomic (10.3.1_git20210424-r2)
(6/12) Installing libgphobos (10.3.1_git20210424-r2)
(7/12) Installing gmp (6.2.1-r0)
(8/12) Installing isl22 (0.22-r0)
(9/12) Installing mpfr4 (4.1.0-r0)
(10/12) Installing mpc1 (1.2.1-r0)
(11/12) Installing gcc (10.3.1_git20210424-r2)
(12/12) Installing .dep (20210629.140945)
Executing busybox-1.33.1-r2.trigger
OK: 122 MiB in 47 packages
/ # gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-alpine-linux-musl/10.3.1/lto-wrapper
Target: x86_64-alpine-linux-musl
Configured with: /home/buildozer/aports/main/gcc/src/gcc-10.3.1_git20210424/configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --build=x86_64-alpine-linux-musl --host=x86_64-alpine-linux-musl --target=x86_64-alpine-linux-musl --with-pkgversion='Alpine 10.3.1_git20210424' --enable-checking=release --disable-fixed-point --disable-libstdcxx-pch --disable-multilib --disable-nls --disable-werror --disable-symvers --enable-__cxa_atexit --enable-default-pie --enable-default-ssp --enable-cloog-backend --enable-languages=c,c++,d,objc,go,fortran,ada --disable-libssp --disable-libmpx --disable-libmudflap --disable-libsanitizer --enable-shared --enable-threads --enable-tls --with-system-zlib --with-linker-hash-style=gnu
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.3.1 20210424 (Alpine 10.3.1_git20210424)
Or directly as document said, remove --virtual:
apk add gcc