---
date: "2007-10-15T06:16:32Z"
title: 'Brain Dump: Random Migration Notes'
---

<!--img src='http://pablotron.org/gallery/misc/brain_dump.png'
  width='273' height='200' align='right' /-->

<p>I've been using the migration and some recent side projects as sandboxes
to try out new things.  Here's a semi-random list of useful tidbits I've
picked up along the way:</p>

<ul>
<li><p>Better mod_rewrite magic:  Google turns up plenty of <a href="http://httpd.apache.org/docs/2.0/mod/mod_rewrite.html">mod_rewrite</a>
examples on automatically stripping the dreaded "www." prefix from
URLs.  Unfortunately, most of them appear to be incorrect.  Here's the
most common solution:</p>

<p><code><pre>RewriteCond %{HTTP_HOST} ^www.example.com$  [NC]
RewriteRule ^(.*)$  http://example.com/$1   [R=301,L]</code></pre></p>

<p>What it's <em>supposed</em> to do is redirect visitors from
<code>http://www.example.com/whatever</code> to <code>http://example.com/whatever</code>,
but what it <em>actually</em> does is redirect visitors to 
<code>http://example.com//whatever</code>.  It's minor, but it was driving me
nuts (Arrrrrrr).  Anyway, here is the correct solution:</p>

<p><code><pre>RewriteCond %{HTTP_HOST} ^www\.             [NC]
RewriteRule ^/(.*)$  http://example.com/$1  [R=301,L]</pre></code></p></li>
<li><p><a href="http://httpd.apache.org/docs/2.0/mod/mod_deflate.html">mod_deflate</a>: Saves a ton of bandwidth, works great in IE7 and 
Firefox.  The stock settings don't include a couple of common MIME
types; here's the list I'm using: 
text/html text/plain text/xml text/css text/javascript
application/x-javascript text/csv</p></li>
<li><a href="http://xcache.lighttpd.net/">XCache</a>: Fast PHP opcode cacher that actually works with recent
versions of PHP.  I tested several <a href="http://wordpress.org/">Wordpress</a>, <a href="http://gallery.menalto.com/">Gallery</a>, and
custom PHP sites without incident, and my (incredibly rough) benchmarks
showed about a 4-7% increase in mean transfer speed.</li>
<li><p><a href="http://extjs.com/download/build">ExtJS Builder</a>: I decided to test the <a href="http://extjs.com/">ExtJS</a> builder for a
personal project.  The interface is a bit finicky; it took me about 5
tries to get all the dependencies for my project selected.  Here are
the results:</p>

<table style='font-size: 9pt; '>
<tr><td>File</td><td>Minified</td><td>Deflated</td></tr>
<tr><td>ext-all.js</td><td>468k</td><td>125k</td></tr>
<tr><td>ext-mine.js</td><td>276k</td><td>77k</td></tr>
</table>

<p>Note: The "Minified" column is the total file size after being shrunk with <a
href='http://javascript.crockford.com/jsmin.html'>Douglas Crockford's
excellent <code>jsmin</code></a>, and the "Deflated" column is 
the actual transfer size (according to <a
href='https://addons.mozilla.org/en-US/firefox/addon/1843'>Firebug</a>) after being passed through
<code>mod_deflate</code>.
</p>

<p>Not too shabby for 20 minutes of work.  I'm a little bit disappointed
by the stock mod_deflate compression ratio, so that may need a bit of
tweaking.</p></li>
<li><p>Backgrounding Mercurial Hooks: The <a href="http://hgbook.red-bean.com/hgbook.html">Mercurial book</a> has an excellent
chapter on hooks.  What it doesn't mention, unfortunately, is how to
run hooks in the background.  I have a semi-lengthy <code>outgoing</code> hook
(roughly equivalent to a client-side <code>post-commit</code> for you Subversion
weenies) that connects to a web server via <code>ssh</code> and performs some
deployment tasks, and all attempts at backgrounding a shell script
eluded me.  Well, it turns out Mercurial has an extra hidden file
descriptor that has to be closed in order to background a hook.  So
here's my down and dirty client-side background deployment hook:</p>

<p><code><pre>
#
# outgoing hook script that connects to web server and deploys
# the latest site from tip.  It is run in the background after a
# successful 'hg push'.
#

# options
opt = {
  # remote hostname
  'host' =&gt; 'web',

  # remote command (relative to my home directory)
  'cmd'  =&gt; 'bin/update_site.sh',

  # client-side log (set to /dev/null to disable)
  # 'log'  =&gt; '/dev/null',
  'log'  =&gt; '/tmp/site_update.log',

  # delay (in seconds) before update
  'delay' =&gt; 3,
}

# fork and run update in background
pid = fork {
  # close stdin, stdout, and stderr
  $stdin = $stdin.reopen('/dev/null', 'r')
  $stdout = $stdout.reopen(opt['log'], 'a')
  $stderr = $stderr.reopen(opt['log'], 'a')
  $defout = $stdout

  # close all other file descriptors
  # NOTE: mercurial appears to have a hidden fd laying 
  # around somewhere, so this evil is necessary...
  (3..99).each { |fd| IO.new(fd).close rescue nil }

  # wait for push to finish
  # (this should poll the hg server instead, to handle
  # lengthy pushes)
  sleep opt['delay']

  # run update command and exit
  args = ['ssh', opt['host'], opt['cmd']]
  exec(*args)

  # never reached
  exit 0
}

# reap child and exit
flags = Process::WNOHANG | Process::WUNTRACED
Process.waitpid(pid, flags)
</pre></code></p></li>
</ul>

<p>
<b>Update:</b> Markdown really mangled my markup this time around.  Usually it's pretty tolerant, but apparently this post was just a bit too much.  Oh well...
</p>