Odds and ends

If you live in or near The Netherlands, don't miss out on The Dutch Open Source Event (T-DOSE) that will be held on 13 and 14 October in Eindhoven. There's an interesting schedule, various projects have booths, and of course, there will be a social event.

Thanks to the tireless effort of Dag and other volunteers almost no West-European event goes by without CentOS presence. T-DOSE is no exception: there will be a booth and talks about dstat (Dag) and CentOS Virtualization (me). We could use additional help at the booth, so if you are interested, please visit the CentOS page for this event and let us know through the CentOS-promo list.

See you this weekend!

As of today, the first CentOS special interest group is active, the Virtualization SIG. A SIG is a smaller group within the CentOS project that focuses on a certain topic, and does promotion, support, and/or development in that area. Besides the creation of the Virtualization SIG, planning for some other SIGs is underway, e.g. an Artwork SIG.

The Virtualization SIG has various technical and support goals. As a part of the latter, the CentOS-virt list was created to discuss virtualization on CentOS and matters related to the virtualization SIG. For more information about the SIG and its goals, please read the announcement message to the CentOS-announce list.

Yay, I am finally moving from a "student room" (studentenkamer) to a more spacious apartment. Fortunately, it's just across a little square that separates two buildings, so I can move all my stuff by foot. Though, my ADSL connection has to be switched over too, so I may drop off the net for a short while ;).

A while ago I switched from DocBook 4.x DTDs to the DocBook 5 RELAX NG schema. RELAX NG supports XML namespaces, I like the compact RELAX NG syntax for its readability, and it is arguably easier to extend than DTDs. While I agree that XML can be painful to edit by hand without a proper editor, XML with proper schemas and stylesheets certainly make writing content easier, especially due to its extensibility. E.g., for a book I am working on, I wanted to extend DocBook to be able to add platform testing information to be able to see in hindsight if I tested a piece of content on every system I want to cover. E.g.:

<sect1 xml:id="somesection">
  <title>Some section</title>

  <platformtests>
      <platform os="Debian GNU/Linux" version="4.0" arch="i386" />
      <platform os="FreeBSD" version="6.2" arch="i386" />
  </platformtests>

  <!-- ... -->
</sect1>

Of course, adding the "platformtests" blocks will be invalid, because they are not described in the schema. This is easily solved by writing a small scheme on top of the DocBook schema:

default namespace db = "http://docbook.org/ns/docbook"

include "docbook.rnc"

dbx.platformtests = element platformtests {
        element platform {
                attribute os { text },
                attribute version { text },
                attribute arch { text }
        }+
}

db.extension.blocks |= dbx.platformtests

This piece of scheme includes the DocBook schema, and defines "platformtests" blocks that can be used at places where normal content blocks can be used (e.g. section bodies). With these schema you can validate DocBook documents with platform tests. Of course, platform tests are not known by the stylesheets, so you will want to modify them to handle "platformtests" elements. In this case, is just a piece of help for me, and I do not want it to show up in HTML or FO documents, so an empty XSL template for this element will handle it fine.

Of course, you can do a lot of other fun stuff with the RELAX NG schemas for DocBook. E.g. Norman Walsh has a nice recipe for making a minimal DocBook variant with relatively little work.

Some CentOS 5 (or Fedora) users may have tried the new C metadata parser for yum, which is significantly faster than the Python-based parser for metadata. Yesterday, I have backported the C metadata parser to yum 2.4 for CentOS 4. It requires a relatively unintrusive patch against yum and a patch against yum-metadata-parser 1.1.0.

Of course, we all want benchmarks :). This is yum on CentOS 4 with the default repositories:

# yum clean all
# time yum whatprovides /bin/ls
[...]
real    0m45.158s
user    0m34.600s
sys     0m0.540s

and with the C metadata parser:

# yum clean all
# time yum whatprovides /bin/ls
[...]
real    0m15.580s
user    0m3.950s
sys     0m0.620s

Looking at the user/sys values, the actual CPU time spent on yum is 35.1 seconds versus 4.6 seconds.

Update: there's a patch for CentOS 3 too. Testing packages are now available through the CentOS Testing repository.