NAME

PAR::Tutorial - Cross-Platform Packaging and Deployment with PAR

SYNOPSIS

This is a tutorial on PAR, first appeared at the 7th Perl Conference. The HTML version of this tutorial is available online as http://search.cpan.org/perldoc?PAR::Tutorial

DESCRIPTION

On Deploying Perl Applications

 % sshnuke.pl 10.2.2.2 -rootpw="Z1ON0101"
 Perl v5.6.1 required--this is only v5.6.0, stopped at sshnuke.pl line 1.
 BEGIN failed--compilation aborted at sshnuke.pl line 1.

* Q: "Help! I can't run your program!"

* A1: Install Perl & perl -MCPAN -e'install(...)'

* How do we know which modules are needed?
* New versions of CPAN modules may break sshnuke.pl

* A2: Install Perl & tar zxf my_perllib.tgz

* Possibly overwriting existing modules; not cross-platform at all

* A3: Use the executable generated by perlcc sshnuke.pl

* Impossible to debug; perlcc usually does not work anyway

PAR, the Perl Archive Toolkit

* Do what JAR (Java Archive) does for Perl

* Aggregates modules, scripts and other files into a Zip file
* Easy to generate, update and extract
* Version consistency: solves forward-compatibility problems
* Developed by community: par@perl.org

* PAR files can be packed into self-contained scripts

* Automatically scans perl script for dependencies

* Bundles all necessary 3rd-party modules with it

* Requires only core Perl to run on the target machine

* PAR also comes with pp, the Perl Packager:

 % pp -o sshnuke.exe sshnuke.pl	# stand-alone executable!

Simple Packaging

* PAR files are just Zip files with modules in it

* Any Zip tools can generate them:

 % zip foo.par Hello.pm World.pm	# pack two modules
 % zip -r bar.par lib/		# grab all modules in lib/

* To load modules from PAR files:

 use PAR;
 use lib "foo.par";		# the .par part is optional
 use Hello;

* This also works:

 use PAR "/home/mylibs/*.par";	# put all of them into @INC
 use Hello;

PAR Loaders

* Use par.pl to run files inside a PAR archive:

 % par.pl foo.par		# looks for 'main.pl' by default
 % par.pl foo.par test.pl	# runs script/test.pl in foo.par

* Same thing, with the stand-alone parl or parl.exe:

 % parl foo.par			# no perl or PAR.pm needed!
 % parl foo.par test.pl		# ditto

* The PAR loader can prepend itself to a PAR file:

* -b bundles non-core modules needed by PAR.pm:

 % par.pl -b -O./foo.pl foo.par	# self-contained script

* -B bundles core modules in addition to -b:

 % parl -B -O./foo.exe foo.par	# self-contained binary

Dependency Scanning

* Recursively scan dependencies with scandeps.pl:

 % scandeps.pl sshnuke.pl
 # Legend: [C]ore [X]ternal [S]ubmodule [?]NotOnCPAN
 'Crypt::SSLeay'       => '0', #  X   #
 'Net::HTTP'           => '0', #      #
 'Crypt::SSLeay::X509' => '0', # S    # Crypt::SSLeay
 'Net::HTTP::Methods'  => '0', # S    # Net::HTTP
 'Compress::Zlib'      => '0', #  X   # Net::HTTP::Methods

* Scan an one-liner, list all involved files:

 % scandeps.pl -V -e "use Dynaloader;"
 ...
 # auto/DynaLoader/dl_findfile.al [autoload]
 # auto/DynaLoader/extralibs.ld [autoload]
 # auto/File/Glob/Glob.bs [data]
 # auto/File/Glob/Glob.so [shared]
 ...

Perl Packager: `pp`

* Combines scanning, zipping and loader-embedding:

 % pp -o out.exe src.pl		# self-contained .exe
 % out.exe			# runs anywhere on the same OS

* Bundle additional modules:

 % pp -o out.exe -M CGI src.pl	# pack CGI + its dependencies, too

* Pack one-liners:

 % pp -o out.exe -e 'print "Hi!"'   # turns one-liner into executable

* Generate PAR files instead of executables:

 % pp -p src.pl			# makes 'source.par'
 % pp -B -p src.pl		# include core modules

How it works

* Command-line options are almost identical to perlcc's

* Also supports gcc-style long options:

 % pp --gui --verbose --output=out.exe src.pl

* Small initial overhead; no runtime overhead

* Dependencies are POD-stripped before packing

* Loads modules directly into memory on demand

* Shared libraries (DLLs) are extracted with File::Temp

* Works on Perl 5.6.0 or above

* Tested on Win32 (VC++ and MinGW), FreeBSD, NetBSD, Linux, MacOSX, Cygwin, AIX, Solaris, HP-UX, Tru64...

Aggregating multiple programs

* A common question:

 > I have used pp to make several standalone applications which work
 > great, the only problem is that for each executable that I make, I am
 > assuming the parl.exe is somehow bundled into the resulting exe.

* The obvious workaround:

 You can ship parl.exe by itself, along with .par files built
 by "pp -p", and run those PAR files by associating them to parl.exe.

* On platforms that have ln, there is a better solution:

 % pp --output=a.out a.pl b.pl	# two scripts in one!
 % ln a.out b.out		# symlink also works
 % ./a.out			# runs a.pl
 % ./b.out			# runs b.pl

Cross-platform Packages

* Of course, there is no cross-platform binary format

* Pure-perl PAR packages are cross-platform by default

* However, XS modules are specific to Perl version and platform
* Multiple versions of a XS module can co-exist in a PAR file

* Suppose we need out.par on both Win32 and Finix:

 C:\> pp --multiarch --output=out.par src.pl
 ...copy src.pl and out.par to a Finix machine...
 % pp --multiarch --output=out.par src.pl

* Now it works on both platforms:

 % parl out.par			# runs src.pl
 % perl -MPAR=out.par -e '...'	# uses modules inside out.par

The Anatomy of a PAR file

* Modules can reside in several directories:

 /			# casual packaging only
 /lib/			# standard location
 /arch/			# for creating from blib/ 
 /i386-freebsd/		# i.e. $Config{archname}
 /5.8.0/		# i.e. Perl version number
 /5.8.0/i386-freebsd/	# combination of the two above

* Scripts are stored in one of the two locations:

 /			# casual packaging only
 /script/		# standard location

* Shared libraries may be architecture- or perl-version-specific:

 /shlib/(5.8.0/)?(i386-freebsd/)?

* PAR files may recursively contain other PAR files:

 /par/(5.8.0/)?(i386-freebsd/)?

Special files

* MANIFEST

* Index of all files inside PAR
* Can be parsed with ExtUtils::Manifest

* META.yml

* Dependency, license, runtime options
* Can be parsed with YAML

* SIGNATURE

* OpenPGP-signed digital signature
* Can be parsed and verified with Module::Signature

Advantages over perlcc, PerlApp and Perl2exe

* This is not meant to be a flame

* All three maintainers have contributed to PAR directly; I'm grateful

* perlcc

* "The code generated in this way is not guaranteed to work... Use for production purposes is strongly discouraged." (from perldoc perlcc)
* Guaranteed to not work is more like it

* PerlApp / Perl2exe

* Expensive: Need to pay for each upgrade
* Non-portable: Only available for limited platforms
* Proprietary: Cannot extend its features or fix bugs
* Obfuscated: Vendor and black-hats can see your code, but you can't
* Inflexible: Does not work with existing Perl installations

MANIFEST: Best viewed with Mozilla

* The URL of MANIFEST inside /home/autrijus/foo.par:

 jar:file:///home/autrijus/foo.par!/MANIFEST

* Open it in a Gecko browser (e.g. Netscape 6+) with Javascript enabled:

* No needed to unzip anything; just click on files to view them

META.yml: Metadata galore

* Static, machine-readable distribution metadata

* Supported by Module::Build, ExtUtils::MakeMaker, Module::Install

* A typical pp-generated META.yml looks like this:

 build_requires: {}
 conflicts: {}
 dist_name: out.par
 distribution_type: par
 dynamic_config: 0
 generated_by: 'Perl Packager version 0.03'
 license: unknown
 par:
   clean: 0
   signature: ''
   verbatim: 0
   version: 0.68

* The par: settings controls its runtime behavior

SIGNATURE: Signing and verifying packages

* OpenPGP clear-signed manifest with SHA1 digests

* Supported by Module::Signature, CPANPLUS and Module::Build

* A typical SIGNATURE looks like this:

 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA1

 SHA1 8a014cd6d0f6775552a01d1e6354a69eb6826046 AUTHORS
 ...
 -----BEGIN PGP SIGNATURE-----
 ...
 -----END PGP SIGNATURE-----

* Use pp and cpansign to work with signatures:

 % pp -s -o foo.par bar.pl	# make and sign foo.par from bar.pl
 % cpansign -s foo.par	# sign this PAR file
 % cpansign -v foo.par	# verify this PAR file

Perl Servlets with Apache::PAR

* Framework for self-contained Web applications

* Similar to Java's "Web Application Archive" (WAR) files
* Works with mod_perl 1.x or 2.x

* A complete web application inside a .par file

* Apache configuration, static files, Perl modules...
* Supports Static, Registry and PerlRun handlers
* Can also load all PARs under a directory

* One additional special file: web.conf

 Alias /myapp/cgi-perl/ ##PARFILE##/
 <Location /myapp/cgi-perl>
     Options +ExecCGI
     SetHandler perl-script
     PerlHandler Apache::PAR::Registry
 </Location>

Hon Dah, A-par-che!

* First, make a hondah.par from an one-liner:

 # use the "web.conf" from the previous slide
 % pp -p -o hondah.par -e 'print "Hon Dah!\n"' \
      --add web.conf
 % chmod a+x hondah.par

* Add this to httpd.conf, then restart apache:

 <IfDefine MODPERL2>
 PerlModule Apache2
 </IfDefine>
 PerlAddVar PARInclude /home/autrijus/hondah.par
 PerlModule Apache::PAR

* Test it out:

 % GET http://localhost/myapp/cgi-perl/main.pl
 Hon Dah!

* Instant one-liner web application that works!

On-demand library fetching

* With LWP installed, your can use remote PAR files:

 use PAR;
 use lib 'http://aut.dyndns.org/par/DBI-latest.par';
 use DBI;    # always up to date!

* Modules are now cached under $ENV{PAR_GLOBAL_TEMP}

* Auto-updates with LWP::Simple::mirror

* Download only if modified
* Safe for offline use after the first time
* May use SIGNATURE to prevent DNS-spoofing

* Makes large-scale deployment a breeze

* Upgrades from a central location
* No installers needed

Code Obfuscation

* Also known as source-hiding techniques

* It is not encryption
* Offered by PerlApp, Perl2Exe, Stunnix...

* Usually easy to defeat

* Take optree dump from memory, feed to B::Deparse
* If you just want to stop a casual grep, "deflate" already works

* PAR now supports pluggable input filters with pp -f

* Bundled examples: Bleach, PodStrip and PatchContent
* True encryption using Crypt::*
* Or even _product activation_ over the internet

* Alternatively, just keep core logic in your server and use RPC

Accessing packed files

* To get the host archive from a packed program:

 my $zip = PAR::par_handle($0);	# an Archive::Zip object
 my $content = $zip->contents('MANIFEST');

* Same thing, but with read_file():

 my $content = PAR::read_file('MANIFEST');

* Loaded PAR files are stored in %PAR::LibCache:

 use PAR '/home/mylibs/*.par';
 while (my ($filename, $zip) = each %PAR::LibCache) {
     print "[$filename - MANIFEST]\n";
     print $zip->contents('MANIFEST');
 }

Packing GUI applications

* GUI toolkits often need to link with shared libraries:

 # search for libncurses under library paths and pack it
 % pp -l ncurses curses_app.pl	# same for Tk, Wx, Gtk, Qt...

* Use pp --gui on Win32 to eliminate the console window:

 # pack 'src.pl' into a console-less 'out.exe' (Win32 only)
 % pp --gui -o out.exe src.pl

* "Can't locate Foo/Widget/Bar.pm in @INC"?

* Some toolkits (notably Tk) autoloads modules without use or require
* Hence pp and Module::ScanDeps may fail to detect them
* Tk problems mostly fixed by now, but other toolkits may still break
* You can work around it with pp -M or an explicit require
* Or better, send a short test-case to par@perl.org so we can fix it

Precompiled CPAN distributions

* Installing XS extensions from CPAN was difficult

* Some platforms do not come with a compiler (Win32, MacOSX...)
* Some headers or libraries may be missing
* PAR.pm itself used to suffer from both problems

* ...but not anymore -- Module::Install to the rescue!

 # same old Makefile.PL, with a few changes
 use inc::Module::Install;	# was "use ExtUtils::MakeMaker;"
 WriteMakefile( ... );		# same as the original
 check_nmake();			# make sure the user have nmake
 par_base('AUTRIJUS');		# your CPAN ID or a URL
 fetch_par() unless can_cc();	# use precompiled PAR only if necessary

* Users will not notice anything, except now it works

* Of course, you still need to type make par and upload the precompiled package
* PAR users can also install it directly with parl -i

Platform-specific Tips

* Win32 and other icon-savvy platforms

* Needs 3rd-party tools to add icons to pp-generated executables
* PE Header manipulation in Perl -- volunteers wanted!

* Linux and other libc-based platforms

* Try to avoid running pp on a bleeding-edge version of the OS
* Older versions with an earlier libc won't work with new ones

* Solaris and other zlib-lacking platforms (but not Win32)

* You need a static-linked Compress::Zlib before installing PAR
* In the future, PAR may depend on Compress::Zlib::Static instead

* Any platform with limited bandwidth or disk space

* Use UPX to minimize the executable size

Thank you!

* Additional resources

* Mailing list: par@perl.org
* Subscribe: Send a blank email to par-subscribe@perl.org
* List archive: http://nntp.x.perl.org/group/perl.par
* PAR::Intro: http://search.cpan.org/dist/PAR/lib/PAR/Intro.pod
* Apache::PAR: http://search.cpan.org/dist/Apache-PAR/
* Module::Install: http://search.cpan.org/dist/Module-Install/

* Any questions?

Bonus Slides: PAR Internals

Overview of PAR.pm's Implementation

* Here begins the scary part

* Grues, Dragons and Jabberwocks abound...
* You are going to learn weird things about Perl internals

* PAR invokes four areas of Perl arcana:

* @INC code references
* On-the-fly source filtering
* Overriding DynaLoader::bootstrap() to handle XS modules
* Making self-bootstrapping binary executables

* The first two only works on 5.6 or later

* DynaLoader and %INC are there since Perl 5 was born
* PAR currently needs 5.6, but a 5.005 port is possible

Code References in @INC

* On 1999-07-19, Ken Fox submitted a patch to P5P

* To _enable using remote modules_ by putting hooks in @INC
* It's accepted to come in Perl 5.6, but undocumented until 5.8
* Type perldoc -f require to read the nitty-gritty details

* Coderefs in @INC may return a fh, or undef to 'pass':

 push @INC, sub {
     my ($coderef, $filename) = @_;  # $coderef is \&my_sub
     open my $fh, "wget ftp://example.com/$filename |";
     return $fh;	# using remote modules, indeed!
 };

* Perl 5.8 let you open a file handle to a string, so we just use that:

        open my $fh, '<', \($zip->memberNamed($filename)->contents);
        return $fh;

* But Perl 5.6 does not have that, and I don't want to use temp files...

Source Filtering without Filter::* Modules

* ... Undocumented features to the rescue!

* It turns out that @INC hooks can return two values
* The first is still the file handle
* The second is a code reference for line-by-line source filtering!

* This is how Acme::use::strict::with::pride works:

 # Force all modules used to use strict and warnings
 open my $fh, "<", $filename or return;
 my @lines = ("use strict; use warnings;\n", "#line 1 \"$full\"\n");
 return ($fh, sub {
     return 0 unless @lines;	
     push @lines, $_; $_ = shift @lines; return length $_;
 });

Source Filtering without Filter::* Modules (cont.)

* But we don't really have a filehandle for anything

* Another undocumented feature saves the day!

* We can actually omit the first return value altogether:

 # Return all contents line-by-line from the file inside PAR
 my @lines = split(
     /(?<=\n)/,
     $zip->memberNamed($filename)->contents
 );
 return (sub {
     $_ = shift(@lines);
     return length $_;
 });

Overriding DynaLoader::bootstrap

* XS modules have dynamically loaded libraries

* They cannot be loaded as part of a zip file, so we extract them out
* Must intercept DynaLoader's library-finding process

* Module names are passed to bootstrap for XS loading

* During the process, it calls dl_findfile to locate the file
* So we install pre-hooks around both functions

* Our _bootstrap just checks if the library is in PARs

* If yes, extract it to a File::Temp temp file

* The file will be automatically cleaned up when the program ends

* It then pass the arguments to the original bootstrap

* Finally, our dl_findfile intercepts known filenames and return it

Anatomy of a Self-Contained PAR executable

* The par script ($0) itself

* May be in plain-text or native executable format

* Any number of embedded files

* Typically used to bootstrap PAR's various dependencies
* Each section begins with the magic string "FILE"
* Length of filename in pack('N') format and the filename (auto/.../)
* File length in pack('N') and the file's content (not compressed)

* One PAR file

* Just a regular zip file with the magic string "PK\003\004"

* Ending section

* A pack('N') number of the total length of FILE and PAR sections
* Finally, there must be a 8-bytes magic string: "\012PAR.pm\012"

Self-Bootstrapping Tricks

* All we can expect is a working perl interpreter

* The self-contained script *must not* use any modules at all
* But to process PAR files, we need XS modules like Compress::Zlib

* Answer: bundle all modules + libraries used by PAR.pm

* That's what the FILE section in the previous slide is for
* Load modules to memory, and write object files to disk
* Then use a local @INC hook to load them on demand

* Minimizing the amount of temporary files

* First, try to load PerlIO::scalar and File::Temp
* Set up an END hook to unlink all temp files up to this point
* Load other bundled files, and look in the compressed PAR section
* This can be much easier with a pure-perl inflate(); patches welcome!

Thank you (again)!

* Any questions, please?

AUTHORS

Audrey Tang <cpan@audreyt.org>

http://par.perl.org/ is the official PAR website. You can write to the mailing list at <par@perl.org>, or send an empty mail to <par-subscribe@perl.org> to participate in the discussion.

Please submit bug reports to <bug-par@rt.cpan.org>.

COPYRIGHT

This document is free documentation; you can redistribute it and/or modify it under the same terms as Perl itself.

See http://www.perl.com/perl/misc/Artistic.html