dfcpp - Dockerfile post-processing by cpanfile.

Automatically creates separate docker layer for each Perl module, mentioned in cpanfile

Simple console utility for Perl developers. Saves time when debugging what is wrong during docker container build.

Problem

It's not possible to run container from layer corresponding to last failed module.

Sometimes you are getting module install error, like Installing WWW::Telegram::BotAPI failed.

It's bit of complicated to define the reason because cpanm puts info about error in a separate file, like /root/.cpanm/work/1517580036.144/build.log, but you can't access this file in case of Docker container build since Docker doesn't save result of failed build.

dfcpp auto-rewrites Dockerfile so that each module is installing by separate command (like RUN cpanm WWW::Telegram::BotAPI), so in new layer (each Dockerfile command = separate layer), instead of installing modules batch way (like cpanm --installdeps .) in a single layer.

This approach saves much time if you have a lot of modules.

To troubleshot you just need to run stopped container, which is the result of last successfully executed command in Dockerfile ( = last successfully installed module).

Example

Dockerfile:

RUN apk update && \
...
cpanm --installdeps . && \
...

cpanfile:

requires 'List::MoreUtils';
requires 'Mojolicious::Lite';
requires 'MongoDB';
requires 'WWW::Telegram::BotAPI';

resulted Dockerfile:

RUN cpanm List::MoreUtils
RUN cpanm Mojolicious::Lite
RUN cpanm MongoDB
RUN cpanm WWW::Telegram::BotAPI

Installing

From Github directly using wget, without git clone

wget https://raw.githubusercontent.com/pavelsr/dfcpp/master/dfcpp.pl -O /usr/bin/dfcpp
chmod +x /usr/bin/dfcpp

For local testing and developing after git clone

sudo ln -s ${PWD}/dfcpp.pl /usr/bin/dfcpp
chmod +x /usr/bin/dfcpp

TO DO

• --help or man
• undo changes
• Python (requirements.txt), Nodejs (package.json) and other languages
• Show latest stopped docker container