Ruby and the Undead

Posted by Tim Brys on Oct 26, 2007

Xen

Docpublisher is nearing it's first internal release, so a lot of testing has been done this week.

For this, a virtual machine running on Xen was used as environment. Not only was it useful for testing purposes, but later on, we will be able to run this same Xen-image on Amazon's EC2 when DocBook publishing will become a hit and scaling will be necessary.

Zombies

During these testing sessions, a bug was encountered, more specifically : an undead bug. Sometimes, when the xmlparser failed to parse a docbookfile, the childprocess it runs in turned zombie and never quit. Luckily, this was quickly fixed by enclosing the fork in a begin..rescue block and then collecting the process 'death signal':

begin
  pid = fork do
    #...
    xmlparser.parse
    #...
end
  #...
rescue
  puts "#{pid} turned zombie, going to kill #{pid}" 
  Process.wait(pid, Process::WNOHANG)
end

Gems

After weeks of copying the core-files to the various transform- and pub lish-directories, I finally decided to make a gem package so that the "libra ry" code is separated from the application-specific code. The gem includes a logger, temp-file manager, message handler and svn wrapper.

Other

• Wrote a lot of documentation (a nice flowchart of the system can be seen here)
• Made code highlighting possible in html of published docbook files
• Implemented support for external xml entities

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