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://aut.dyndns.org/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?

SEE ALSO

http://www.autrijus.org/par-tutorial/

http://www.autrijus.org/par-intro/ (English version)

http://www.autrijus.org/par-intro.zh/ (Chinese version)

PAR, pp, par.pl, parl

ex::lib::zip, Acme::use::strict::with::pride

App::Packer, Apache::PAR, CPANPLUS, Module::Install

AUTHORS

Autrijus Tang <autrijus@autrijus.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

Copyright 2003, 2004, 2005 by Autrijus Tang <autrijus@autrijus.org>.

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