Perl Development Environment Tooling

Perl Development
Environment Tooling
Jason Crome
Technical Lead, All Around the World
August 25, 2016 Copyright 2016, Jason A. Crome

Who’s this for?
• Devs who need to work with multiple versions of Perl
(module authors, large enterprises, masochists, etc.)
• Devs who have been through dependency hell
• Devs who need a speciﬁc Perl setup but system restrictions
interfere
• Devs looking to make deployment easier
• People frustrated with bugs in system Perl
• People who want to use/test the latest Perl features
Copyright 2016, Jason A. CromeAugust 25, 2016

What We’ll Cover
• local::lib
• perlbrew
• plenv
• Carton
• Carmel and Pinto (very minimally)

local::lib
• Helps work with system Perl
• Helps avoid sysadmins
• Makes deployments easier
• Installs Perl modules to home (or another) directory,
rather than updating the system lib/ directory.

local::lib… But why?
• Sometimes you can’t install the Perl you need
• Sometimes you install from packages (Debian,
FreeBSD, etc.) that don’t update often.
• Sometimes your sysadmin is cautious and prevents
you from installing what you need

About local::lib
• Your local modules take precedence
• Your local modules have no effect on other users
• System Perl doesn’t even need local::lib
installed for you to use it! (to do this, look at the
bootstrapping technique)

Using local::lib
# Initialize local::lib (.bashrc, etc.)
eval $( perl -Mlocal::lib );
# Install a module
cpanm Dancer2
# In your code:
# Nothing, you already set this up in your shell :)

perlbrew and plenv
• Helps avoid system Perl
• Helps avoid system admins
• Makes deployments easier
• Useful for testing an app against other Perl versions
• Install one or more Perl versions to your home directory
• More ﬂexible than local::lib

perlbrew and plenv
jason@darwin PerlDancer/Dancer2-official (master)
7:22:47 git » plenv versions
system
aaw-5.22.0
bump-5.24.0
crome-plated
dancer-5.10.1
* dancer-5.22.0 (set by ~/Projects/PerlDancer/.perl-version)
fifo-5.22.0
pearlbee-5.18.4
vetminder-5.22.0
vetminder-5.24.0
veure-5.18.4
veure-5.22.1
veure-5.24.0
waste-classic
waste-tng

perlbrew and plenv
• Not compatible with each other
• If you want to switch after you have installed one of
these, you must completely uninstall the other

perlbrew - Pros and Cons
• It’s easy
• Don’t need sudo to install Perl modules
• Onus is placed on dev to change Perl versions
when it is appropriate to do so
• When you switch Perl versions, you stay on that
version until you switch to another

How perlbrew Works
• By abusing your $PATH, that’s how.
• When you switch versions of Perl, perlbrew changes
your path to point to the desired version of Perl
• Does this by exporting some shell functions that
switches $PATH when needed
• Easy to understand
• Written in Perl

Installing perlbrew
# From the shell (all you should really need)
curl -L https://install.perlbrew.pl | bash
perlbrew init
# Or, from CPAN
sudo cpan App::perlbrew

Using perlbrew
# What versions can be installed?
perlbrew available
# Install a version
perlbrew install perl-5.24.0
# List installed versions
perlbrew list
# Change versions
perlbrew switch perl-5.18.4
# Test against all installed versions
perlbrew exec dzil test

plenv - Pros and Cons
• Lets you set local and global Perl conﬁgs
• This leaves .perl-version ﬁles in its wake. Add
to .gitignore
• No $PATH munging to work
• Less functionality than perlbrew out of the box

How plenv works
• Installs to one location and adds it to your path
• Creates a shim for each executable (base Perl plus
those added through CPAN)
• Implemented in bash (no global shell functions)
• Shim looks at the appropriate .perl-version ﬁle
to determine which Perl version to use

What’s in .perl-version?
jason@darwin Projects/veure (master*)
10:57:21 git » cat .perl-version
veure-5.24.0

Installing plenv
# On mac?
brew install plenv
brew install perlbuild

Installing plenv
# Otherwise
git clone https://github.com/tokuhirom/plenv.git ~/.plenv
echo 'export PATH="$HOME/.plenv/bin:$PATH"' >>
~/.bash_profile
echo 'eval "$(plenv init -)"' >> ~/.bash_profile
exec $SHELL -l
git clone https://github.com/tokuhirom/Perl-Build.git
~/.plenv/plugins/perl-build/

Using plenv
# What versions can be installed?
plenv install --list
# Install a version
plenv install 5.24.0
plenv install 5.24.0 --as dancer2-5.24.0
# List installed versions
plenv versions
# Change versions
plenv local dancer2-5.24.0
plenv global system
# Test against all installed versions (need plenv-contrib)
plenv exec-all dzil test

Carton
• Top-notch dependency management
• Can specify a speciﬁc range of allowed versions,
or a speciﬁc one. This is huge!
• Runs your app with only the modules you specify
• Super-easy to deploy and distribute your app with
no module/dependency hell

Why’s this useful?
• Consider Veure (Tau Station, our game)
• Developer stymied by test failures
• Only one on team using Test::Class::Moose 0.77
• Spend inordinate amount of time tracking down to ﬁnd
it was a version issue
• Better dependency/module management would have
made this a non-issue

How Carton works
• Uses cpanfile to specify versions
• Can create a cpanfile.snapshot to pin speciﬁc
versions that are currently installed
• Distribute these to other machines with your
application to deploy/run your app

What’s in .cpanfile?
# This version and any after
requires “Dancer2", ">= 0.163000”;
# No specific version needed
requires "Dancer2::Plugin::Database" => 0;
on "test" => sub {
requires “Test::More" => "0";
requires “Test::Class::Moose”, ”>= 0.73, < 0.77”;
};

Installing Carton
# From CPAN
cpanm Carton

Using Carton
# Install module version listed in cpanfile from CPAN
carton install
# Modules are installed to local/
# Version info captured to cpanfile.snapshot
# Commit to github
git add cpanfile.snapshot
git commit -m”Capture module version snapshot.”
git push
# Clone to other machine, then
carton install --deployment
# Now, run your app
carton exec plackup sbin/app.psgi

Bundling with Carton
• carton bundle bundles the tarballs for your
modules and their dependencies into a directory
• Easy to distribute across a local network
• Deploy via carton install --cached
• Can install without CPAN or an internet connection

A ﬁnal note
• Carton creates two things in your project directory:
local/ and .carton
• These should not be distributed with your app
• Make it easy: add to .gitignore

Carmel and Pinto
Honestly, I have little experience here
Both are marked experimental.
USE AT YOUR OWN RISK

Carmel
• Set up your own CPAN-like repositories of modules
• Carmel keeps a repo of all modules you build with
it
• When you need a module, uses cpanfile to
determine what it needs from that repo and builds
@INC appropriately.
• Carmel and Carton are made to work together

Pinto
• Pinto works like a self-curated PAUSE/CPAN
• Unlike CPAN, lets you keep different module versions
for dev, prod, test, etc.
• Has version control. Easy to rollback if you add a
broken module release
• Allows you to use only modules and versions you want
• Works when you are ofﬂine/CPAN is down

Thank you!

Resources
• local::lib - https://metacpan.org/pod/local::lib
• perlbrew - https://perlbrew.pl/
• plenv - https://github.com/tokuhirom/plenv
• Carton - https://metacpan.org/pod/Carton
• Carmel - https://metacpan.org/pod/Carmel
• Pinto - https://metacpan.org/pod/Pinto

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