CPAN

Hans Dieter Pearcey (hdp@cpan.org)

needs

• don't reinvent wheels
• keep code fresh
• be pragmatic

meta

• some complete solutions
• some toolkit pieces
• some flying cars

human factors

• sysadmins
• managers
• yourself

sysadmins

• shouldn't have to learn Perl
• don't want to deal with install failures
• want to use tools they know
• like consistency

managers

• politics are sometimes incomprehensible
• they're still your problem

yourself

• finite amount of time & energy
• not an expert on everything

lowest common denominator

$ cpan Foo::Bar

• universal
• core
• simple

problems

• requires root
• few management tools
• missing information:
  • file list (sometimes)
  • dist version
• runs tests each time

vendor packages

• "can't you just?"
• often stale
• often nonexistant
• wrong priorities
  • vendor/sysadmin vs. developer

Pull from a newer version

• e.g. Debian apt preferences
• apt-get install -t unstable libmoose-perl
• may pull in too much
  • the 5.8 -> 5.10 change
  • (re)build from source packages?
• may not be available for your OS
  • Gentoo
  • any others?

build vendor packages

• dh-make-perl
  • or something else vendor-specific
• cpan2dist
  • backends for Debian, RPM, Gentoo, etc.

cpan2dist --format CPANPLUS::Dist::Gentoo Foo::Bar

caveats

• upgrading dual-life modules
• vendor versions vs. CPAN versions
  • version.pm 0.74 is libversion-perl 1:0.7400
  • 0.33 <=> 0.2802?

wrap site_perl (Debian)

cpan2dist --format CPANPLUS::Dist::Deb
  --defaults --dist-opts distdir=`pwd`/debs
  Foo::Bar

• install into site_perl
• named cpan-libfoo-bar-perl
• provides
  • cpan-libfoo-bar-perl
  • libfoo-bar-perl
• automatically prefers Debian's packages

caveats

• silent conflicts with vendor packages
  • site_perl > vendor in @INC
  • /usr/local/bin > /usr/bin in $PATH
• miss out on vendor QA

bonus: PAR

• PAR::Dist packs up dists

Foo-Bar-1.23$ make && perl -MPAR::Dist -e blib_to_par

• PAR::Dist::install_par -- unpack and make install
  • /path/to/file.par
  • http://my.dist.host/file.par
  • cpan://AUTHOR/file.par
• keeps (but does not install) META.yml
• glue potential

flying cars

• seamless use of vendor vs. auto-built packages
  • cpan2pkg
• richer dependencies
  • external libraries
  • Alien::

unsolved problems

• requires root
• per-machine, not per-application
• metaphor shear

local::lib

~$ eval $(perl -Mlocal::lib)

• gives you a private library directory
  • install without root
• API / glue for
  • prereqs (consistancy)
  • installation
  • use lib
  • $PATH

default

• ~/perl5
• shared webhost
• shared developer machine

echo 'eval $(perl -I$HOME/perl5/lib/perl5 -Mlocal::lib)'
  >> ~/.bashrc

per-application libraries

in your shell

~/code/MyApp$ eval $(perl -Mlocal::lib=./local)

in scripts/*

use FindBin ();
use local::lib "$FindBin::Bin/../local";

per-application libraries

• bundle dependencies
• rsync, tarball, etc.
• useful for:
  • multiple disparate programmers or teams
  • large applications with independent lifecycles
  • stability / mission-criticality
  • standalone applications

generate MyApp::local

make-local-lib.pl

• use MyApp::local in scripts or MyApp.pm
  • just like use lib ...

# script/myapp_runstuff.pl
use MyApp::local;

• or, like Catalyst scripts

# script/myapp_runstuff.pl
use FindBin;
use lib "$FindBin::Bin/../lib";
use MyApp::local;

self-contained

~/code/MyApp$ perl
  -Mlocal::lib=--self-contained,./local
  -MCPAN -e 'install q(.)'

• all non-core dependencies
• note: --self-contained affects only that process + children
  • no affect on the environment
  • cannot be transmitted by the shell

ups and downs

• bugfixes applied per-application
  • only break one application at a time
• repeated installing and testing

bonus: distroprefs

• YAML, Data::Dumper, Storable
• automate installs via CPAN.pm
• match: dist filename, module, perl version, %Config, %ENV
• change: commandlines, environment, CPAN config
• apply patches, drive Expect

example

HDP.Perl-Version.yml

example

FDALY.Test-Deep.yml

distroprefs rock

• capture a dist's build process
• make it repeatable
• local::lib + distroprefs = win

flying cars

• tools for per-application local::lib
  • Platypus (remedie)
  • installer integration
• bundle dependencies with your dist
  • push @INC, File::ShareDir::dist_dir('My-Dist');

client vs. server

• so far all client-side
• seize the means of production

client vs. server

• so far all client-side
• seize the means of production distribution
  • CPAN itself

mirror CPAN

• cpan CPAN::Mini
• minicpan -l ~/cpan -r http://www.perl.org/CPAN
• repeat as needed to update
• latest non-development release of every module
  • what CPAN clients see

benefits

• speed
• network connectivity
• upgrades fit your schedule
• consistency between installs

still lacking

• fine control over upgrades
  • manual review
  • testing
• changelog

filter / augment

• CPAN::Mini::Inject
• CPAN::Mini::Devel
• CPAN::Mini::Tested / CPxxxAN
• all of the above

flying cars

• CPAN mirror filtering tools
  • test vs. internal code
  • test reverse dependents
  • external criteria (RT bugs, CPAN ratings, etc.)
• create CPAN mirror from Debian perl sources

bonus ideas

• vendor packages + local::lib
• automate local::lib for upgrade testing
• distribute your own perl

the end

thank you!