Here’s a mail telling how the Config::Model Perl module was used to refactor existing configuration tools in Perl. Some punctuation and blank lines were added to improve the flow of this text. The full name and mail address of gkr is withheld on his request.

I took over a perl script that was responsible to pull data from several sources and push it after validation and re-packaging including some meta data into one of our production systems.

The script was never intended to be used for more then a few month. But as things go, we were still using it after a few years. Only now for a lot more sources. Since all the configuration of sources and meta data were contained as a single hash in this script, it became very unwieldy. Although the configuration seldom changed, once it got added it was not an option to keep it like this especially as we decided to prepare a Debian package for faster installation and version tracking. So I had to re-work it and was looking for some library that was allowing me to define how the configuration has to look like, providing sensible hard coded and computed defaults for some of the values.

This was when I found Config::Model on Cpan. It was, after some digging into the documentation, quite simple to define a rough first version of the complete config, including global default values as ini file and very simple to read in and write out. A more advanced version was not working because the Config::Model in Debian squeeze did not provide needed features.

Switching to yaml as configuration file format not only increased readability but also worked with the standard Squeeze package. Consistency is checked automatically inside the model so broken configurations are more unlikely in the future.

Of course I had some work re-factoring the original source but Config::Model allowed an easy addition of a value-checked and documented configuration file. To access the Config::Model::Instance I added small wrapper packages that allowed an easy access of the config elements by name to make the source easier to understand. The re-factoring needed for creating a Debian package for the Script – which is now a set of modules and a small executable – was simple once I had Config::Model working, since I was able to add new configuration items effortlessly and remove a lot of hard coded parameters.

I don’t use the cli tool yet for configuration editing but that’s going to be the next step.

Many thanks to gkr for this feedback. Let’s hope he will continue to give feedback on his usage of Config::Model.

All the best

Like all kids, my kids really enjoy watching cartoons. Unfortunately, most of them are broadcast during the morning, sometimes very early in the morning. Since I don’t want my kids to wake up (or wake me up…) too early in the morning to watch cartoon, I record the most interesting programs with vdr (I also edit out commercials before my kids watch them)

To limit my carbon (or equivalent radio-active waste) footprint, I do not want to leave the computer on 24/24, so the machine has to power up by itself before a recording time.

So I’ve setup vdr to automatically setup the wake up time of the computer and shutdown the machine once the recording is finished. Note that this machine is also my main home machine, so it must not shutdown while I’m working on it (typing this blog, for instance).

This should have been easy and fairly documented. Well, it was not that easy. A lot of doc mentions nvram-wakeup which is more or less obsolete. Other docs were in German. So, here’s a summary of the setup so other can benefit from my experience.

First, this was done on a Debian/sid machine, this post should be usable on other distros, provided some adaptations. These adaptations are left as an exercise to the reader (which is marketing lingo for “I don’t have a clue”)

First add this line in /etc/default/vdr:

 ENABLE_SHUTDOWN=1

When vdr has nothing to do, it will run some shutdown scripts, including /usr/share/vdr/shutdown-hooks/S90.custom, which is a link to /etc/vdr/shutdown-hooks/S90.custom.

The output of this script will be eval’ed by vdr, so vdr knows what to do next (e.g. abort shutdown, display a message to user, retry later…).

Here are the possible output of a vdr shutdown script (list taken from vdr-wiki):

• To abort the shutdown, exit with an errorlevel != 0.
• If you want a message to be displayed on the OSD when aborting a shutdown,
  then write to stdout:
  ABORT_MESSAGE=<message to display>
• If you want to defer the shutdown, write to stdout:
  TRY_AGAIN=<minutes to wait before next shutdown request>
• To overwrite the command that will be executed to shutdown the machine
  after all shutdown hooks have been processed, write to stdout:
  SHUTDOWNCMD=<new shutdown command>
  i.e.:
  echo "ABORT_MESSAGE=\"I do not want to shutdown now!\"" ; exit 1

This script will mess with /sys/class/rtc/rtc0/wakealarm so it must be run as root. But vdr will launch this script and does not run as root. Instead of setting a suid bit, let’s setup sudo to enable this script to gain root privilege from vdr. Add this line in /etc/sudoers (with visudo):

vdr ALL= NOPASSWD: /etc/vdr/shutdown-hooks/S90.custom *

And here’s a commented Perl script that handle the shutdown test:

#!/usr/bin/perl
use IO::File ;
use 5.10.0 ;
use English;
use Path::Class; 

use Sys::Syslog qw(:standard :macros);  # standard functions & macros
openlog('vdr-shutdown', "", "user");

Here’s the call to sudo to gain root privilege (if not already run as root):

if ($EUID) {
    system('sudo','/etc/vdr/shutdown-hooks/S90.custom', @ARGV) ;
    syslog(info => "vdr-shutdown: sudo myself returned $@") ;
}

Get the next timer info from the command arguments provided by vdr:

my ($next_timer,$interval) = @ARGV ;

Setup the next alarm in the mother board:

if ( $next_timer) {
  my $dev_fh = IO::File->new("> /sys/class/rtc/rtc0/wakealarm");
  die "cannot open $dev_fh: $!" unless $dev_fh ;
  my $newtime = $next_timer - 300  ;  # Start 5 minutes earlier
  $dev_fh->print( "$newtime\n" ) ;
  $dev_fh->close ;

  syslog(info => "vdr-shutdown: set wakeup to $newtime") ;
}

Now, let’s check if someone is logged on the system. Weirdly enough, forking a command from this Perl script does not work when it’s run by vdr. Calling the ‘who’ command always return empty. The trick to find if anyone is logged is to check the content of /dev/pts directory. No files in there means that nobody is logged:

my @pts  = dir('/dev/pts')->children;
syslog(info => "vdr-shutdown:  found pts @pts") ;

if (@pts > 1) {
    syslog(info => "vdr-shutdown: retry later: someone is logged") ;
    say 'ABORT_MESSAGE="someone is logged, shutting down deferred"';
    say 'TRY_AGAIN=30'
}
else {
    syslog(info => "vdr-shutdown: nobody is logged, halting") ;
}

Now some cleanup then exit:

closelog() ;

exit 0;

This script has been working for one month, and not a single programs was missed. My kids are happy.

I’m not so happy because I now have a lot of commercials to edit out

All the best

Last week-end, I’ve participated Perl/QA hackathon in Paris.

Here’s a short summary of the main activities during this week-end. I was not in the best of shape due to a nasty (biological) bug that wore me down before the hackathon.

First of all, I discussed with rjbs about the bunch of debian patches I’ve written for Software::License. These patches (and hacks) are used in Debian to provide licenses summaries in Debian::Dpkg::Copyright model to help write Debian copyright files. License management is boring but necessary. cme and Software::License help in making this task slightly less boring. Ricardo kindly suggested some modifications and agreed to include my patches. I implemented these modifications directly during the hackathon.

The other tasks during this week-end were (not necessarily in that order):

• I discussed with alanhaggai and gave him some ideas to fix his Archive::Zip module
• I did a live demo of Debian packaging to ribasushi: I updated the Debian package libdbix-class-schema-loader-perl from CPAN and uploaded it in Debian.
• I presented how to package Perl modules for Debian. renormalist will package his own module Data::Dpath and its dependencies for Debian. I will sponsor his packages once they are available on Debian perl’s team git repository. Unless gregoa beats me to it
• I discussed with Slaven Rezic some binding weirdness found in Perl/Tk HList. Config::Model’s graphical interface provide a viewer widget and and editor widget for configuration items. As expected, the viewer is invoked by a single left click. One would expect a double click to invoke the editor widget. But the double click bindinngdoes not owrk in HList when the single click is used. Currently the editor widget is invoked with a right-click, which is not user-friendly. According to Slaven, the bug might be hidden quite deep in Perl/Tk guts. Fixing it won’t be easy.
• As a Debian/sid user, I’ve been quite spoiled: I’ve always had a recent Perl available on my system. I’ve neved had to compile Perl since my HPUX days back in last century. However, Config;:Model tests failed with Perl 5.15.9, a development version not available in Debian (sid is not that unstable). Thanks to Xavier Caron, I’ve learned about perlbrew and cpanminus to reproduce this bug and fix the issue. Many apologies to miyagawa for asking dumb questions about cpanm: the disctinction between runtime and build time does not apply to cpan minus. I guess that’s the drawback of wearing 2 hats (Debian dev hat and Perl dev hat): your brain may get confused and you conflate issues. Oops.

Many thanks to FreeSide who sponsored my travel, to the hackathons organisers and to all the participants for their welcome.

All the best

As maintainer of libwx-scintilla-perl, I had to update the package to update a dependency declation to close bug #662427. The dependency was good enough for the package to work but it blocked the linpng15 transition.

This is yet another detail to remember when updating package: whether the dependencies are impacted by a transition. As I’m really bad at remembering such details, I’ve added the relevant check in the dpkg control source model used by cme.

Now running ‘cme check dpkg’ will warn you if a dependency impacts a transition. And ‘cme fix dpkg’ will fix you dependency list as resquested by a transition. Well, that holds true for the transition I’m aware of. Feel free to contact me if more transition checks are needed.

For those who are curious (or want to send me a patch for another transition), here’s the actual implementation of these new checks.

All the best

I’ve (finally) released a new version of Config::Model. The main change for users is the deprecation of the config-edit program in favor of cme program. Instead of using options, this cme uses command keywords like git, so users will have more possibilities while typing less. bash completion is provided for cme command and options.

Following Debian annoucement regarding the recommended format of Debian copyright file (aka DEP-5), I’ve also updated the URL in Debian copyright model. If your package is already in a DEP-5 format, you can update the URL with this simple command:

cme fix dpkg-copyright

Check the wiki on github for more example of cme command.

All the best

In Debian package, the debian/control file has a specific syntax where each line must begin with a space and paragraphs are separated by a single ‘.’. If you want to follow DEP-5 syntax for debian/copyright files, you have a similar problem when comes the time to fill the license text for creative-common license: it’s easy to miss a space or a dot.

Let’s say I want to add a new section in the description of my package. Here’s the current description:

Description: module to automate definition of a DBIx::Class::Schema
 DBIx::Class::Schema::Loader is an extension to DBIx::Class that automates the
 definition of a DBIx::Class::Schema by scanning table schemas and setting up
 columns and primary keys appropriately. It supports MySQL, PostgreSQL, SQLite
 and DB2.
 .
 Bare table definitions are fairly straightforward, but relationship creation
 is somewhat heuristic, especially with respect to choosing relationship types
 and names, as well as join types. The relationships generated by this module
 will probably never be as well-defined as hand-generated ones.

I want to add “This package is awesome” but I don’t want to be bothered by leading dots and white spaces.

First, I go in the package directory, then check the syntax with cme:

$ cme check dpkg

Then create a loop directory, where the dpkg content will be mapped to a fuse directory:

$ mkdir loop
$ cme fusefs dpkg -fuse-dir loop/
Mounting config on loop/ in background.
Use command 'fusermount -u loop/' to unmount
$ cat loop/control/binary/libdbix-class-schema-loader-perl/Description 
DBIx::Class::Schema::Loader is an extension to DBIx::Class that automates the
definition of a DBIx::Class::Schema by scanning table schemas and setting up
columns and primary keys appropriately. It supports MySQL, PostgreSQL, SQLite
and DB2.

Bare table definitions are fairly straightforward, but relationship creation
is somewhat heuristic, especially with respect to choosing relationship types
and names, as well as join types. The relationships generated by this module
will probably never be as well-defined as hand-generated ones.

Then edit loop/control/binary/libdbix-class-schema-loader-perl/Description with your favorite editor.

For the sake of this blog, I will use echo to edit this file:

$ echo -e "\nThis module is awesome" >> loop/control/binary/libdbix-class-schema-loader-perl/Description

Now umount the loop (note that the actual debian/control is not changed before this step):

fusermount -u loop

Now the result:

$ cat debian/control 
[...]
Description: module to automate definition of a DBIx::Class::Schema
 DBIx::Class::Schema::Loader is an extension to DBIx::Class that automates the
 definition of a DBIx::Class::Schema by scanning table schemas and setting up
 columns and primary keys appropriately. It supports MySQL, PostgreSQL, SQLite
 and DB2.
 .
 Bare table definitions are fairly straightforward, but relationship creation
 is somewhat heuristic, especially with respect to choosing relationship types
 and names, as well as join types. The relationships generated by this module
 will probably never be as well-defined as hand-generated ones.
 .
 This module is awesome

Here’s another example to fill the license text for a license while respecting DEP-5 syntax, (done after the cme command):

# creating this dir will create a new DEP-5 
# standalone license section with name CC-BY-30
mkdir loop/copyright/License/CC-BY-30
# fill the text part of the  license
wget http://creativecommons.org/licenses/by/3.0/legalcode -O - \
 | html2text -style pretty > loop/copyright/License/CC-BY-30/text
$ fusermount -u loop
$ cat debian/copyright
[...]
License: CC-BY-30
 .
 .
 .
                                Creative_Commons
 .
 .
 Creative Commons Legal Code
 .
 .
 Attribution 3.0 Unported
[...]

And that’s it. (note that cme command is new and is available only from version 2.004 of Config::Model)

Of course, there’s more than a awy to do it: you can also run cme edit dpkg and add or edit license text in the GUI (or in an editor launched by the GUI). cme will take care of the syntax details.

All the best

Thanks to the effort of Felix Geyer (debfx) and Manuel Montecelo (mafm), most of SDL packages in Debian unstable are now up-to-date. These guys did a really great job: most of the time, I could upload the packages they prepared without modification. These guys should become DD, they have the skills. Ok, debfx has started the process (congrats) and mafm is still thinking about it…

Anyway, here the messages for all those who gave up packaging new SDL games for Debian because of stale SDL packages: SDL team is alive, the core SDL packages are now up-to-date, the wait is over.

This is true also for Perl SDL games: I’ve uploaded yesterday the latest Perl bindings to SDL. Unfortunately, this upload broke some games like frozen-bubble, pangzero and dizzy. But new versions compatible with new SDL perl are available upstream so theses games won’t be broken for long.

All the best

Following the suggestions provided after my post “What name for Config::Model’s new command line ? cfg or something else ?“, I’ve considered “cmc” and “cme” as a good candidates. But, “cmc” is used by a “C mol compiler” software (don’t ask me what it is…). “cme” is also a very good name.

So the winner is “cme”

Next version of Config::Model will provide /usr/bin/cme. The old config-edit command will be provided for a few months to preserve backward compatibility.

Thanks to all people who took the time to reply

All the best

As Damyan mentioned last summer in Debconf, the current command interface to Config::Model Perl module is rather cumbersome as it involves quite a lot of typing. First, config-edit command name is too long. Even with the help bash completion, this does not compare well with git or hg command. Then all operation require options. For instance, the -application option is required to specify what you will be working on. A required option is a good example of an oxymoron. Which may be funny but which is not user friendly…

So, here’s the synopsis of the new command I’m working on:

# edit dpkg config with GUI (Tk or curses, or readline)
cfg edit dpkg 
  
# just check the validity of the file, show warnings
# and suggested fixes
# does not modify the file
cfg check dpkg
  
# check the file, remove deprecated parameters,
# migrate data to new parameters and save
cfg migrate dpkg 
  
# like migrate, but also apply all suggested fixes
cfg fix dpkg 

# like migrate and modify configuration 
# with command line argument
cfg modify dpkg source format="quilt (3.0)"
  
# access dpkg parameters through a fuse file
# system. data are saved when fs is unmounted
cfg fusefs dpkg fuse-dir

# dump configuration data in config-model format
cfg dump dpkg   

# list all available applications
cfg list 
  
# more general synopsis
cfg [ global_options ] command application [ options ] arguments

This synopsis use dpkg as an example, but it could be used for any of the available models (e.g. ssh, lcdproc, multistrap …).

The main question I have for you is: Is cfg name good ? I mean it’s short, descriptive enough. But it’s also quite ugly. Does anyone have a better idea ?

And what do you think of the synopsis shown above ? Are the sub-command name descriptive enough ?

All the best

Most SDL packages are outdated, people are complaining in the BTS, and the team is mostly inactive.

That’s bad news for my project. What can I do ?

Well, it’s Debian project, I just have to step up.

Thanks to Sam Hocevar, I’m now admin on Debian Alioth SDL packaging project.

I’d like to revive the team. (Note that I don’t have the bandwidth to be the team all by myself).

Here are the first steps I plan (mostly inspired by the way Debian-perl team is working):

• create a SDL-team page on debian wiki (done)
• setup a SDL packaging git repo so that team members can collaborate more easily on packaging (on-going)
• call for volunteers to help. (this message is the first step)
• review and upload packages from team members

Now, there are some ground rules I wish to push forward:

• any team member can work on any package maintained by the team.
• just tell us on this list about any work you are doing (to avoid duplication)
• send a mail on this list if you need a package to be reviewed for upload.
• you can use SDL subversion repository to work on a package
• you can also use SDL git repo to work on a package (please discuss with us for the migration steps)
• once a package is migrated to git, it cannot go back to subversion.

If you don’t agree with the above points, now is the time to say it.

Feel free to join by:

1. Creating an account on Alioth
2. request to join sdl-team
3. Last but not least, send a short introduction mail to pkg-sdl-maintainers AT lists.alioth.debian.org so we can know each other.

See you soon