Difference between pages "OpenStack Architecture" and "The Gentoo.org Redesign, Part 1"

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This page exists to document [http://www.openstack.org OpenStack] configuration.
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{{Article
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|Subtitle=A site reborn
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|Summary=Have you ever woken up one morning and suddenly realized that your cute little personal development Web site isn't really that great? If so, you're in good company. In this series, Daniel Robbins shares his experiences as he redesigns the www.gentoo.org Web site using technologies like XML, XSLT, and Python. Along the way, you may find some excellent approaches to use for your next Web site redesign. In this article, Daniel creates a user-centric action plan and introduces pytext, an embedded Python interpreter.
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|Author=Drobbins
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}}
 +
==  An unruly horde ==
  
Note that the current approach is to use devstack, which is not a good way to learn OpenStack. So much of this document will be about doing a devstack-like configuration for Funtoo.
+
Fellow software developer, may I ask you a question? Why is it that although many of us are intimately familiar with Web technologies such as HTML, CGI, Perl, Python, Java technology, and XML, our very own Web sites -- the ones devoted to our precious development projects -- look like they were thrown together by an unruly horde of hyperactive 12-year-olds? Why, oh why, is this so?
  
This document will split OpenStack configuration into each architectural component, describing configuration steps for each component separately.
+
Could it be because most of the time, we've left our Web site out to rot while we squander our precious time hacking away on our free software projects? The answer, at least in my case, is a most definite "Yes."
  
== SQL Database ==
+
When I'm not writing articles for IBM developerWorks or being a new dad, I'm feverishly working on the next release of Gentoo Linux, along with my skilled team of volunteers. And, yes, Gentoo Linux has its own Web site (see Resources). As of right now (March 2001), our Web site isn't that special; that's because we don't spend much time working on it because we're generally engrossed in improving Gentoo Linux itself. Sure, our site does have several admittedly cute logos that I whipped up using Xara X (see Resources), but when you look past the eye candy, our site leaves a lot to be desired. Maybe yours does too. If so, I have one thing to say to you -- welcome to the club.
  
A number of OpenStack services use a SQL back-end for storing various bits of data.
+
==  www.gentoo.org ==
  
While DevStack uses MySQL for its SQL deployment, multiple database back-ends are actually supported thanks to [http://sqlalchemy.org SQLAlchemy] being used behind the scenes, which is a re-targetable Python database API. Thus, it should be possible to use Postgres, etc, by simply using different connection strings. A list of SQLAlchemy connection types can be found on [http://docs.sqlalchemy.org/en/latest/core/engines.html this SQLAlchemy documentation page.]
+
In our case, our Web site dilemma exists because our project has been growing, and our Web site hasn't. Now that Gentoo Linux is approaching the 1.0 release (when it'll be officially ready for non-developers) and is growing in popularity, we need to start seriously looking at how our Web site can better serve its users. Here's a snapshot of www.gentoo.org:
  
Using a single root database user account for all services is not a good policy for production deployment. Ideally, each service should have its own restricted user account with only the ability to access its own database.
+
<div style="margin: 10px;">[[File:L-redesign-01.gif|frame|class=img-responsive|The current (March 2001) state of affairs at www.gentoo.org]]</div>
  
Let's look at how each service is configured in regards to SQL:
+
As you can see, we have all the bare essentials -- a description of Gentoo Linux, a features list, a daily Changelog (automatically updated thanks to Python), and a bunch of important links (to the download sites, to our mailing list sign-up pages, and to cvsWeb). We also have links to three documentation resources -- the Gentoo Linux Install Guide and Development Guides, and Christian Zander's NVIDIA Troubleshooting Guide.
  
=== nova ===
+
However, while the site seems O.K., we're missing a lot of things. The most obvious is documentation -- our installation and development guides need a lot of work. And then we need to add an FAQ, new links, new user information...the list is endless.
  
Here's how to set up a MySQL database back-end for nova and tell nova to initialize its database tables:
+
== Content vs. display ==
  
<console>
+
And now we come to our second problem. Right now, all of our work is done in raw HTML; I hack away at the index.html file until it looks O.K. Even worse, our Web documentation is written in raw HTML. This isn't a good thing from a development perspective because our raw content (consisting of paragraphs, sections, chapters) is garbled together with a bunch of display-related HTML tags. This, of course, makes it difficult to change both the content and the look of our site. While this approach has worked so far, it is bound to cause problems as our site continues to grow.
mysql> ##i##create database nova character set latin1;
+
Query OK, 1 row affected (0.02 sec)
+
  
mysql> ##i##grant all privileges on nova.* to nova@localhost identified by 'foobar';
+
Clearly, we need to be using better technologies behind the scenes. Instead of using HTML directly, we need to start using things like XML, XSLT, and Python. The goal is to automate as much as possible so that we can add and expand our site with ease. If we do our job well, even major future changes to our site should be relatively painless.
Query OK, 0 rows affected (0.00 sec)
+
</console>
+
  
Now set the following connection string in <tt>/etc/nova/nova.conf</tt>:
+
== A strategy! ==
  
<pre>
+
It was clear that we had a lot of work ahead of us. In fact, there was so much to be done that I didn't know where to begin. Just as I was trying to sort out everything in my head, I came across Laura Wonnacott's "Site Savvy" InfoWorld column (see Resources). In it, she explained the concept of "user-centric" design -- how to improve a Web site while keeping the needs of your target audience (in this case, Gentoo Linux users and developers) in focus. Reading the article and taking a look at the "Handbook of User-Centered Design" link from the article helped me to formulate a strategy -- an action plan -- for the redesign:
--sql_connection=mysql://nova:foobar@localhost/nova
+
</pre>
+
  
Note the use of the latin1 character set when we created the tables in MySQL. This is so the following command will not cause an error due to the default UTF-8 character set creating indexes that are too big for MySQL to handle:
+
# First, clearly define the official goal of the Web site -- in writing. What's it there for, and what's it supposed to do?
 +
#  Identify the different categories of users who will be using your site -- your target audience. Rank them in order of priority: Which ones are most important to you?
 +
# Set up a system for getting feedback from your target audience, so they can let you know what you're doing right and wrong.
 +
# Evaluate the feedback, and use it to determine what parts of the site need to be improved or redesigned. Tackle high-priority sections first.
 +
# Once you've selected the part of the site to improve, get to work! During your implementation, make sure that the content and design of the new section caters specifically to the needs of your target audience and fixes all known deficiencies.
 +
# When the section redesign is complete, add it to your live site, even if it has a look that's markedly different from your current site. This way, your users can begin benefitting from the newly redesigned section immediately. If there's a problem with the redesign, you'll get user feedback more quickly. Finally, making incremental improvements to your site (rather than revamping the whole site and then rolling it out all at once -- surprise!) will help prevent your users from feeling alienated by your (possibly dramatic) site changes.
 +
#  After completing step 6, jump to step 4 and repeat.
  
<console>
+
== The mission statement ==
# ##i##nova-manage db sync
+
2012-03-02 21:31:14 DEBUG nova.utils [-] backend <module 'nova.db.sqlalchemy.migration' from '/usr/lib64/python2.7/site-packages/nova/db/sqlalchemy/migration.pyc'> from (pid=17779) __get_b
+
ackend /usr/lib64/python2.7/site-packages/nova/utils.py:602
+
</console>
+
  
After running the command above, you should now have all the relevant database tables created:
+
I was happy to discover that we already had step 3 in place. We had received several e-mail suggestions from visitors to the site, and our developer mailing list also served as a way of exchanging suggestions and comments. However, I had never really completed steps 1 or 2. While the answers may seem obvious, I did find it helpful to actually sit down and write out our mission statement:
  
<console>
+
www.gentoo.org exists to assist those who use and develop for Gentoo Linux by providing relevant, up-to-date information about Gentoo Linux and Linux in general, focusing on topics related to Gentoo Linux installation, use, administration, and development. As the central hub for all things Gentoo, the site should also feature important news relevant to Gentoo Linux users and developers. In addition to catering to Gentoo Linux users and developers, www.gentoo.org has the secondary purpose of meeting the needs of potential Gentoo Linux users, providing the information they need to decide whether Gentoo Linux is right for them.
xdev var # ##i##mysql -u root -p nova
+
Enter password:
+
Reading table information for completion of table and column names
+
You can turn off this feature to get a quicker startup with -A
+
  
Welcome to the MySQL monitor.  Commands end with ; or \g.
+
== The target audience ==
Your MySQL connection id is 16
+
Server version: 5.1.61-log Gentoo Linux mysql-5.1.61
+
  
Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
+
So far, so good. Now for step 2 -- defining our target audience:
  
Oracle is a registered trademark of Oracle Corporation and/or its
+
www.gentoo.org has three target audiences -- Gentoo Linux developers, users, and potential users. While no one group is absolutely a higher priority than another, right now the needs of Gentoo Linux developers are our highest priority, followed by Gentoo Linux users, and then potential users. This is because Gentoo Linux is currently in a prerelease state. When Gentoo Linux reaches version 1.0, Gentoo Linux users and potential users will also become a priority.
affiliates. Other names may be trademarks of their respective
+
owners.
+
  
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
+
== Comments and suggestions ==
  
mysql> ##i##show tables;
+
O.K., now it's time to evaluate the suggestions and comments we've collected:
+-------------------------------------+
+
| Tables_in_nova                      |
+
+-------------------------------------+
+
| agent_builds                        |
+
| aggregate_hosts                    |
+
| aggregate_metadata                  |
+
| aggregates                          |
+
| auth_tokens                        |
+
| block_device_mapping                |
+
| bw_usage_cache                      |
+
| certificates                        |
+
| compute_nodes                      |
+
| console_pools                      |
+
...
+
</console>
+
  
You have now validated that nova is connecting to your MySQL database correctly.
+
Over the past few months, we've received a number of suggestions from Web site visitors. Overwhelmingly, people are requesting better documentation -- for both developers and users. Several developers have asked if we could create a mailing list that would be devoted exclusively to describing CVS commits.
  
=== glance ===
+
Interestingly, we've also received a couple of e-mails asking whether Gentoo Linux is a commercial or free product. I'm guessing that because our main logo is inscribed with the name "Gentoo Technologies, Inc." (our legal corporation name), people assume that we have a commercial focus. Modifying our logo so that it reads "Gentoo Linux" and adding small opening paragraph to the main page explaining that we are a free software project should help.
  
From glance.openstack.org:
+
== The improvement list ==
  
<blockquote>The Glance project provides services for discovering, registering, and retrieving virtual machine images. Glance has a RESTful API that allows querying of VM image metadata as well as retrieval of the actual image.</blockquote>
+
O.K., now let's turn these suggestions into a list of possible improvements:
  
Glance typically uses a MySQL database called <tt>glance</tt>, although the name is configurable in the connection string.
+
* Revamp main page
 +
** Implementation: update logo and add free software blurb
 +
** Goal: to clearly state that we are a free software project
 +
** Target group: potential users
 +
**  Difficulty: medium
 +
* Improve basic user documentation
 +
**  Implementation: new XML/XSLT system, verbose documentation
 +
** Goal: to make it easier for users to install Gentoo Linux
 +
** Target group: new users
 +
** Difficulty: medium
 +
*Improve/create developer documentation
 +
** Implementation: new XML/XSLT system, CVS guide, dev guide, Portage guide
 +
**  Goal: to help our developers to do a great job
 +
** Target group: developers
 +
** Difficulty: hard
 +
*Add a CVS mailing list
 +
** Implementation: use our existing mailman mailing list manager
 +
** Goal: to better inform our developers
 +
** Target group: developers
 +
** Difficulty: easy
  
SQL connection settings might be stored in a glance configuration file located at <tt>/opt/stack/glance/etc/glance-registry.conf</tt>. In the devstack installation process, <tt>/opt/stack/glance</tt> contains a git checkout of the glance software.
+
== A selection! ==
  
The SQL connection configuration string might look something like this:
+
Two things leap out from the list, for different reasons. The first is the CVS mailing list -- this one is a no-brainer because it's so easy to implement. Often, it makes sense to implement the easiest changes first so that users can benefit from them right away.
  
<pre>
+
The second big thing that leaps out from the list is the need for developer documentation. This is a longer-term project that will require much more work. From my conversations with the other developers, we all appear to be in agreement that some kind of XML/XSL approach is the right solution.
sql_connection = mysql://glance:yourpassword@192.168.206.130/glance
+
</pre>
+
  
More info on glance configuration is available [http://docs.openstack.org/diablo/openstack-compute/install/content/glance-registry-conf-file.html here].
+
== The XML/XSL prototype ==
  
=== keystone ===
+
To help start the process, I developed a prototype XML syntax to be used for all our online documentation. By using this XML syntax (called "guide"), our documentation will be clearly organized into paragraphs, sections, and chapters (using XML tags like <section>, <chapter>, etc.) while remaining free of any display-related tags. To create the HTML for display on our site, I created a prototype set of XSL transforms. By using an XSLT processor such as Sablotron, our guide XML files can be converted into HTML as follows:
  
Keystone, the OpenStack identity service, also uses SQL. <tt>etc/keystone.conf</tt> keystone install/git repo directory is used to store the SQL configuration:
+
devguide.xml + guide.xsl ---XSLT processor---> devguide.html
  
<pre>
+
The great thing about this XML/XSLT approach is that it separates our raw content (XML) from the display-related information contained in the guide.xsl (XSLT) file. If we ever need to update the look of our Web pages, we simply modify the guide.xsl file and run all our XML through the XSLT processor (Sablotron), creating updated HTML pages. Or, if we need to add a few chapters to the development guide, we can modify devguide.xml. Once we're done, we then run the XML through Sablotron, which then spits out a fully-formatted devguide.html file with several added chapters. Think of XML as the content and XSLT as the display-related formatting macros.
sql_connection = %SQL_CONN%
+
</pre>
+
  
As everything else, the SQL connection string uses SQLAlchemy syntax.
+
While our entire team is convinced that XML/XSLT is the way to go, we haven't yet agreed upon an official XML syntax. Achim, our development lead, suggested that we use docbook instead of rolling our own XML syntax. However, the prototype guide XML format has helped to start the decision-making process. Because we developers are going to be the ones using the XML/XSL on a daily basis, it's important to choose a solution that we're comfortable with and meets all of our needs. By my next article, I should have a working XML/XSL doc system to show off to you.
  
=== Quantum and Open VSwitch ===
+
== Technology demo: pytext ==
  
<blockquote>Quantum is an incubated OpenStack project to provide "network connectivity as a service" between interface devices (e.g., vNICs) managed by other Openstack services (e.g., nova).</blockquote>
+
For the most part, our current Web site isn't using any new or super-cool technologies that are worth mentioning. However, there's one notable exception -- our tiny pytext embedded Python interpreter.
  
[http://openvswitch.org Open VSwitch] is described as:
+
Like many of you, I'm a huge Python fan and much prefer it over other scripting languages, so when it came time to add some dynamic content to our Web site, I naturally wanted to use Python. And, as you probably know, when coding dynamic HTML content, it's usually much more convenient to embed the language commands inside the HTML, rather than the other way around. Thus, the need for an embedded Python interpreter that can take a document like this:
  
<blockquote>Open vSwitch is a production quality, multilayer virtual switch licensed under the open source Apache 2.0 license. It is designed to enable massive network automation through programmatic extension, while still supporting standard management interfaces and protocols (e.g. NetFlow, sFlow, SPAN, RSPAN, CLI, LACP, 802.1ag). In addition, it is designed to support distribution across multiple physical servers similar to VMware's vNetwork distributed vswitch or Cisco's Nexus 1000V. </blockquote>
+
<pre>
 
+
<p>
There is an [http://openvswitch.org/openstack/documentation/ Open VSwitch Plug-in for OpenStack Quantum] which can be set up by DevStack. This plug-in uses SQL storage. The SQLAlchemy connection string is stored in (relative to git/install root) <tt>etc/quantum/plugins/openvswitch/ovs_quantum_plugin.ini</tt>. Similarly to everything but nova, the SQL connection string is stored in <tt>sql_connection =</tt> format.
+
Yeah, sure; I got some questions:<br>
 +
<!--code
 +
names=["bob","jimmy","ralph"]
 +
items=["socks","lunch","accordion"]
 +
for x in items:
 +
for y in names:
 +
print "Anyone seen",y+"'s",x+"?<br>"
 +
-->
 +
See, told you so.
 +
</pre>
  
If the plugin is enabled, the following settings are added to nova.conf:
+
....and transform it into this:
  
 
<pre>
 
<pre>
--libvirt_vif_type=ethernet
+
<p>
--libvirt_vif_driver=nova.virt.libvirt.vif.LibvirtOpenVswitchDriver
+
Yeah, sure; I got some questions:<br>
--linuxnet_interface_driver=nova.network.linux_net.LinuxOVSInterfaceDriver
+
Anyone seen bob's socks?<br>
--quantum_use_dhcp
+
Anyone seen jimmy's socks?<br>
 +
Anyone seen ralph's socks?<br>
 +
Anyone seen bob's lunch?<br>
 +
Anyone seen jimmy's lunch?<br>
 +
Anyone seen ralph's lunch?<br>
 +
Anyone seen bob's accordion?<br>
 +
Anyone seen jimmy's accordion?<br>
 +
Anyone seen ralph's accordion?<br>
 +
See, told you so.
 
</pre>
 
</pre>
  
=== Melange ===
+
Here's the source code for pytext:
  
From the Melange site:
+
Code Listing 2.4:  
 +
{{file|name=pytext|lang=python|desc=The pytext embedded Python interpreter|body=
 +
#!/usr/bin/env python2
  
<blockquote>
+
# pytext 2.1
Melange is intended to provide network information services for use across OpenStack services. The initial focus will be on IP address management (IPAM) and address discovery (DHCP/dnsmasq) functionality. Melange is intended to be a standalone service with it's own API. However, the initial use case will be to decouple existing IP management and VM address discovery from Nova and support the existing Nova networking capabilities.
+
# Copyright 1999-2001 Daniel Robbins
</blockquote>
+
# Distributed under the GPL
  
Melange also uses a <tt>sql_connection =</tt> string stored in its <tt>etc/melange/melange.conf</tt> (relative to install/git root).
+
import sys
  
== RabbitMQ ==
+
def runfile(myarg):
 +
  "interprets a text file with embedded elements"
 +
  mylocals={}
 +
  try:
 +
      a=open(myarg,'r')
 +
  except IOError:
 +
      sys.stderr.write("!!! Error opening "+myarg+"!\n")
 +
      return
 +
  mylines=a.readlines()
 +
  a.close()
 +
  pos=0
 +
  while pos<len(mylines):
 +
      if mylines[pos][0:8]=="<!--code":
 +
  mycode=""
 +
  pos=pos+1
 +
  while (pos<len(mylines)) and (mylines[pos][0:3]!="-->"):
 +
      mycode=mycode+mylines[pos]
 +
      pos=pos+1
 +
  exec(mycode,globals(),mylocals)
 +
      else:
 +
  sys.stdout.write(mylines[pos])
 +
      pos=pos+1
  
RabbitMQ  is a reliable messaging framework used by OpenStack. Currently, it looks like only nova uses it. Nova is configured to connect to rabbitmq by setting the following lines in <tt>/etc/nova/nova.conf</tt>:
+
if len(sys.argv)>1:
 +
  for x in sys.argv[1:]:
 +
      runfile(x)
 +
  sys.exit(0)
 +
else:
 +
  sys.stderr.write
 +
    ("pytext 2.1 -- Copyright 1999-2001 Daniel Robbins. ")
 +
  sys.stderr.write
 +
    ("Distributed under the\nGNU Public License\n\n")
 +
  sys.stderr.write
 +
    ("Usage: "+sys.argv[0]+" file0 [file1]...\n")
 +
  sys.exit(1)
 +
}}
 +
 
 +
== How pytext works ==
 +
 
 +
Here's how it works. It scans each input line, and most of the time, each input line is simply echoed to stdout. However, if pytext encounters a line beginning with <!--code, then the contents of every line up to the first line beginning with --> are appended to a string called mycode. Pytext then executes the mycode string using the built-in exec() function, effectively creating an embedded Python interpreter.
 +
 
 +
There's something really beautiful about this particular implementation -- we call exec() in such a way that all modifications to the global and local namespaces are saved. This makes it possible to import a module or define a variable in one embedded block, and then access this previously-created object in a later block, as this example clearly demonstrates:
  
 
<pre>
 
<pre>
--rabbit_host=$RABBIT_HOST
+
<!--code
--rabbit_password=$RABBIT_PASSWORD
+
import os
 +
foo=23
 +
-->
 +
 
 +
Hello
 +
 
 +
<!--code
 +
print foo
 +
if os.path.exists("/tmp/mytmpfile"):
 +
print "it exists"
 +
else:
 +
print "I don't see it"
 +
-->
 
</pre>
 
</pre>
  
Rabbit's password is configured using the following command, as root:
+
Handy, eh? pytext serves is an excellent demonstration of the power of Python, and is an extremely useful tool for Python fans. For our current site, we call pytext from a cron job, using it to periodically generate the HTML code for our main page Changelog:
  
 
<console>
 
<console>
# ##i##rabbitmqctl change_password guest $RABBIT_PASSWORD
+
$ ##i##pytext index.ehtml > index.html
 
</console>
 
</console>
  
I am not yet completely sure how RabbitMQ fits into the OpenStack architecture. It may be that the supporting services expect it to be running locally, and that Nova compute nodes need to hook into a Nova instance, which would typically be running remotely. (Thus the ability for DevStack to target a remote RabbitMQ host.)
+
That's it for now; I'll see you next time when we'll take a look at the first stage of the www.gentoo.org redesign!
 
+
{{ArticleFooter}}
== Virtualization Technology ==
+
 
+
DevStack defaults to configuring OpenStack to use libvirt with [[KVM]], and will fall back to basic [[QEMU]] support if the <tt>kvm</tt> kernel module is not available. It also has support for using libvirt with [[LXC]], in addition to using [[Xen]] Server directly (bypassing libvirt.)
+
 
+
 
+
[[Category:Virtualization]]
+
[[Category:OpenStack]]
+

Revision as of 08:21, December 31, 2014

A site reborn

Have you ever woken up one morning and suddenly realized that your cute little personal development Web site isn't really that great? If so, you're in good company. In this series, Daniel Robbins shares his experiences as he redesigns the www.gentoo.org Web site using technologies like XML, XSLT, and Python. Along the way, you may find some excellent approaches to use for your next Web site redesign. In this article, Daniel creates a user-centric action plan and introduces pytext, an embedded Python interpreter.

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An unruly horde

Fellow software developer, may I ask you a question? Why is it that although many of us are intimately familiar with Web technologies such as HTML, CGI, Perl, Python, Java technology, and XML, our very own Web sites -- the ones devoted to our precious development projects -- look like they were thrown together by an unruly horde of hyperactive 12-year-olds? Why, oh why, is this so?

Could it be because most of the time, we've left our Web site out to rot while we squander our precious time hacking away on our free software projects? The answer, at least in my case, is a most definite "Yes."

When I'm not writing articles for IBM developerWorks or being a new dad, I'm feverishly working on the next release of Gentoo Linux, along with my skilled team of volunteers. And, yes, Gentoo Linux has its own Web site (see Resources). As of right now (March 2001), our Web site isn't that special; that's because we don't spend much time working on it because we're generally engrossed in improving Gentoo Linux itself. Sure, our site does have several admittedly cute logos that I whipped up using Xara X (see Resources), but when you look past the eye candy, our site leaves a lot to be desired. Maybe yours does too. If so, I have one thing to say to you -- welcome to the club.

www.gentoo.org

In our case, our Web site dilemma exists because our project has been growing, and our Web site hasn't. Now that Gentoo Linux is approaching the 1.0 release (when it'll be officially ready for non-developers) and is growing in popularity, we need to start seriously looking at how our Web site can better serve its users. Here's a snapshot of www.gentoo.org:

The current (March 2001) state of affairs at www.gentoo.org

As you can see, we have all the bare essentials -- a description of Gentoo Linux, a features list, a daily Changelog (automatically updated thanks to Python), and a bunch of important links (to the download sites, to our mailing list sign-up pages, and to cvsWeb). We also have links to three documentation resources -- the Gentoo Linux Install Guide and Development Guides, and Christian Zander's NVIDIA Troubleshooting Guide.

However, while the site seems O.K., we're missing a lot of things. The most obvious is documentation -- our installation and development guides need a lot of work. And then we need to add an FAQ, new links, new user information...the list is endless.

Content vs. display

And now we come to our second problem. Right now, all of our work is done in raw HTML; I hack away at the index.html file until it looks O.K. Even worse, our Web documentation is written in raw HTML. This isn't a good thing from a development perspective because our raw content (consisting of paragraphs, sections, chapters) is garbled together with a bunch of display-related HTML tags. This, of course, makes it difficult to change both the content and the look of our site. While this approach has worked so far, it is bound to cause problems as our site continues to grow.

Clearly, we need to be using better technologies behind the scenes. Instead of using HTML directly, we need to start using things like XML, XSLT, and Python. The goal is to automate as much as possible so that we can add and expand our site with ease. If we do our job well, even major future changes to our site should be relatively painless.

A strategy!

It was clear that we had a lot of work ahead of us. In fact, there was so much to be done that I didn't know where to begin. Just as I was trying to sort out everything in my head, I came across Laura Wonnacott's "Site Savvy" InfoWorld column (see Resources). In it, she explained the concept of "user-centric" design -- how to improve a Web site while keeping the needs of your target audience (in this case, Gentoo Linux users and developers) in focus. Reading the article and taking a look at the "Handbook of User-Centered Design" link from the article helped me to formulate a strategy -- an action plan -- for the redesign:

  1. First, clearly define the official goal of the Web site -- in writing. What's it there for, and what's it supposed to do?
  2. Identify the different categories of users who will be using your site -- your target audience. Rank them in order of priority: Which ones are most important to you?
  3. Set up a system for getting feedback from your target audience, so they can let you know what you're doing right and wrong.
  4. Evaluate the feedback, and use it to determine what parts of the site need to be improved or redesigned. Tackle high-priority sections first.
  5. Once you've selected the part of the site to improve, get to work! During your implementation, make sure that the content and design of the new section caters specifically to the needs of your target audience and fixes all known deficiencies.
  6. When the section redesign is complete, add it to your live site, even if it has a look that's markedly different from your current site. This way, your users can begin benefitting from the newly redesigned section immediately. If there's a problem with the redesign, you'll get user feedback more quickly. Finally, making incremental improvements to your site (rather than revamping the whole site and then rolling it out all at once -- surprise!) will help prevent your users from feeling alienated by your (possibly dramatic) site changes.
  7. After completing step 6, jump to step 4 and repeat.

The mission statement

I was happy to discover that we already had step 3 in place. We had received several e-mail suggestions from visitors to the site, and our developer mailing list also served as a way of exchanging suggestions and comments. However, I had never really completed steps 1 or 2. While the answers may seem obvious, I did find it helpful to actually sit down and write out our mission statement:

www.gentoo.org exists to assist those who use and develop for Gentoo Linux by providing relevant, up-to-date information about Gentoo Linux and Linux in general, focusing on topics related to Gentoo Linux installation, use, administration, and development. As the central hub for all things Gentoo, the site should also feature important news relevant to Gentoo Linux users and developers. In addition to catering to Gentoo Linux users and developers, www.gentoo.org has the secondary purpose of meeting the needs of potential Gentoo Linux users, providing the information they need to decide whether Gentoo Linux is right for them.

The target audience

So far, so good. Now for step 2 -- defining our target audience:

www.gentoo.org has three target audiences -- Gentoo Linux developers, users, and potential users. While no one group is absolutely a higher priority than another, right now the needs of Gentoo Linux developers are our highest priority, followed by Gentoo Linux users, and then potential users. This is because Gentoo Linux is currently in a prerelease state. When Gentoo Linux reaches version 1.0, Gentoo Linux users and potential users will also become a priority.

Comments and suggestions

O.K., now it's time to evaluate the suggestions and comments we've collected:

Over the past few months, we've received a number of suggestions from Web site visitors. Overwhelmingly, people are requesting better documentation -- for both developers and users. Several developers have asked if we could create a mailing list that would be devoted exclusively to describing CVS commits.

Interestingly, we've also received a couple of e-mails asking whether Gentoo Linux is a commercial or free product. I'm guessing that because our main logo is inscribed with the name "Gentoo Technologies, Inc." (our legal corporation name), people assume that we have a commercial focus. Modifying our logo so that it reads "Gentoo Linux" and adding small opening paragraph to the main page explaining that we are a free software project should help.

The improvement list

O.K., now let's turn these suggestions into a list of possible improvements:

  • Revamp main page
    • Implementation: update logo and add free software blurb
    • Goal: to clearly state that we are a free software project
    • Target group: potential users
    • Difficulty: medium
  • Improve basic user documentation
    • Implementation: new XML/XSLT system, verbose documentation
    • Goal: to make it easier for users to install Gentoo Linux
    • Target group: new users
    • Difficulty: medium
  • Improve/create developer documentation
    • Implementation: new XML/XSLT system, CVS guide, dev guide, Portage guide
    • Goal: to help our developers to do a great job
    • Target group: developers
    • Difficulty: hard
  • Add a CVS mailing list
    • Implementation: use our existing mailman mailing list manager
    • Goal: to better inform our developers
    • Target group: developers
    • Difficulty: easy

A selection!

Two things leap out from the list, for different reasons. The first is the CVS mailing list -- this one is a no-brainer because it's so easy to implement. Often, it makes sense to implement the easiest changes first so that users can benefit from them right away.

The second big thing that leaps out from the list is the need for developer documentation. This is a longer-term project that will require much more work. From my conversations with the other developers, we all appear to be in agreement that some kind of XML/XSL approach is the right solution.

The XML/XSL prototype

To help start the process, I developed a prototype XML syntax to be used for all our online documentation. By using this XML syntax (called "guide"), our documentation will be clearly organized into paragraphs, sections, and chapters (using XML tags like <section>, <chapter>, etc.) while remaining free of any display-related tags. To create the HTML for display on our site, I created a prototype set of XSL transforms. By using an XSLT processor such as Sablotron, our guide XML files can be converted into HTML as follows:

devguide.xml + guide.xsl ---XSLT processor---> devguide.html

The great thing about this XML/XSLT approach is that it separates our raw content (XML) from the display-related information contained in the guide.xsl (XSLT) file. If we ever need to update the look of our Web pages, we simply modify the guide.xsl file and run all our XML through the XSLT processor (Sablotron), creating updated HTML pages. Or, if we need to add a few chapters to the development guide, we can modify devguide.xml. Once we're done, we then run the XML through Sablotron, which then spits out a fully-formatted devguide.html file with several added chapters. Think of XML as the content and XSLT as the display-related formatting macros.

While our entire team is convinced that XML/XSLT is the way to go, we haven't yet agreed upon an official XML syntax. Achim, our development lead, suggested that we use docbook instead of rolling our own XML syntax. However, the prototype guide XML format has helped to start the decision-making process. Because we developers are going to be the ones using the XML/XSL on a daily basis, it's important to choose a solution that we're comfortable with and meets all of our needs. By my next article, I should have a working XML/XSL doc system to show off to you.

Technology demo: pytext

For the most part, our current Web site isn't using any new or super-cool technologies that are worth mentioning. However, there's one notable exception -- our tiny pytext embedded Python interpreter.

Like many of you, I'm a huge Python fan and much prefer it over other scripting languages, so when it came time to add some dynamic content to our Web site, I naturally wanted to use Python. And, as you probably know, when coding dynamic HTML content, it's usually much more convenient to embed the language commands inside the HTML, rather than the other way around. Thus, the need for an embedded Python interpreter that can take a document like this:

<p>
Yeah, sure; I got some questions:<br>
<!--code
names=["bob","jimmy","ralph"]
items=["socks","lunch","accordion"]
for x in items:
for y in names:
print "Anyone seen",y+"'s",x+"?<br>"
-->
See, told you so.

....and transform it into this:

<p>
Yeah, sure; I got some questions:<br>
Anyone seen bob's socks?<br>
Anyone seen jimmy's socks?<br>
Anyone seen ralph's socks?<br>
Anyone seen bob's lunch?<br>
Anyone seen jimmy's lunch?<br>
Anyone seen ralph's lunch?<br>
Anyone seen bob's accordion?<br>
Anyone seen jimmy's accordion?<br>
Anyone seen ralph's accordion?<br>
See, told you so.

Here's the source code for pytext:

Code Listing 2.4:

pytext (python source code) - The pytext embedded Python interpreter
#!/usr/bin/env python2
 
# pytext 2.1
# Copyright 1999-2001 Daniel Robbins
# Distributed under the GPL
 
import sys
 
def runfile(myarg):
   "interprets a text file with embedded elements"
   mylocals={}
   try:
      a=open(myarg,'r')
   except IOError:
      sys.stderr.write("!!! Error opening "+myarg+"!\n")
      return
   mylines=a.readlines()
   a.close()
   pos=0
   while pos<len(mylines):
      if mylines[pos][0:8]==""):
       mycode=mycode+mylines[pos]
       pos=pos+1
  exec(mycode,globals(),mylocals)
       else:
  sys.stdout.write(mylines[pos])
       pos=pos+1
 
if len(sys.argv)>1:
   for x in sys.argv[1:]:
       runfile(x)
   sys.exit(0)
else:
   sys.stderr.write
     ("pytext 2.1 -- Copyright 1999-2001 Daniel Robbins. ")
   sys.stderr.write
     ("Distributed under the\nGNU Public License\n\n")
   sys.stderr.write
     ("Usage: "+sys.argv[0]+" file0 [file1]...\n")
   sys.exit(1)

How pytext works

Here's how it works. It scans each input line, and most of the time, each input line is simply echoed to stdout. However, if pytext encounters a line beginning with are appended to a string called mycode. Pytext then executes the mycode string using the built-in exec() function, effectively creating an embedded Python interpreter.

There's something really beautiful about this particular implementation -- we call exec() in such a way that all modifications to the global and local namespaces are saved. This makes it possible to import a module or define a variable in one embedded block, and then access this previously-created object in a later block, as this example clearly demonstrates:

<!--code
import os
foo=23
-->

Hello

<!--code
print foo
if os.path.exists("/tmp/mytmpfile"):
print "it exists"
else:
print "I don't see it"
-->

Handy, eh? pytext serves is an excellent demonstration of the power of Python, and is an extremely useful tool for Python fans. For our current site, we call pytext from a cron job, using it to periodically generate the HTML code for our main page Changelog:

$ pytext index.ehtml > index.html

That's it for now; I'll see you next time when we'll take a look at the first stage of the www.gentoo.org redesign!


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Have you ever woken up one morning and suddenly realized that your cute little personal development Web site isn't really that great? If so, you're in good company. In this series, Daniel Robbins shares his experiences as he redesigns the www.gentoo.org Web site using technologies like XML, XSLT, and Python. Along the way, you may find some excellent approaches to use for your next Web site redesign. In this article, Daniel creates a user-centric action plan and introduces pytext, an embedded Python interpreter.
About the Author

Daniel Robbins is best known as the creator of Gentoo Linux and author of many IBM developerWorks articles about Linux. Daniel currently serves as Benevolent Dictator for Life (BDFL) of Funtoo Linux. Funtoo Linux is a Gentoo-based distribution and continuation of Daniel's original Gentoo vision.

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