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Link: http://code.google.com/speed/page-speed/docs/caching.html#LeverageBrowserCaching
This post describes two ways to ensure the javascript and CSS are requested by the browser when a new release is distributed.
The first approach is to prefix the file names with a version-release string, and create symlinks to the files during installation or the first execution. Many systems have a version identification mechanism.
To manage the symlinks, the following could be used:
Code:
#!/bin/bash | |
| |
fclearold() | |
{ | |
echo 'fclearold' | |
for g in $(find *.$1 -maxdepth 1 -type l);do | |
echo $g | |
rm -f $g | |
done | |
} | |
| |
fcreatenew() | |
{ | |
echo 'fcreatenew' | |
for g in $(ls *.$1); do | |
ln -s $g $2.$g | |
done | |
| |
} | |
| |
version=`cat "$BASE/config/version`; | |
for f in 'js' 'css'; do | |
echo $f | |
pushd $f > /dev/null | |
fclearold $f | |
echo $version; | |
fcreatenew $f $version | |
popd > /dev/null | |
done |
fclearold removes the old symlinks, fcreatenew makes new ones. It is assumed the javascript is in the js directory and all javascript files have a .js extension, and the CSS is in the css directory and all CSS files have a .css extension.
httpd.conf (or equivalent)
Code:
# Cache js and CSS files for 6 months - with a timestamp | |
<FilesMatch "\.(js|css)$"> | |
ExpiresActive On | |
ExpiresDefault "access plus 6 months" | |
Header set Cache-Control "max-age=15552000" | |
RewriteEngine On | |
RewriteRule (.*)/[0-9]+\.(.*)$ $1/$2 | |
FileETag MTime | |
</FilesMatch> |
Timestamp Management Code (PHP)
PHP:
function sTimestamp() | |
{ | |
$sTimestampFile = 'cache/timestamp'; | |
if (is_file($sTimestampFile)) | |
$sRetVal = file_get_contents($sTimestampFile); | |
else | |
{ | |
$sRetVal = time(); | |
file_put_contents($sTimestampFile,$sRetVal); | |
} | |
return $sRetVal; | |
} |
Once the timestamp is set, it is cached in the cache/timestamp file. In this system, the cache is cleared when new releases are installed, so the absence of the timestamp file ensures an update and a new set of requested files.
The timestamp can applied to .js and .css file requests like so:
PHP:
<script type="text/javascript" src="js/<?php echo $timestamp ?>.code.js"></script> |
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