Drupal's existing caching mechanism doesn't perform well on highly dynamic websites in which the cache is flushed frequently. One example is a site that is under attack by a spambot that is posting spam comments every few seconds, causing all cached pages to be flushed every few seconds. Loose caching immediately flushes the cache only for specific users who have modified cached data (whether or not they are logged in), delaying the flushing of data for other users by several minutes.
(I rewrote the help text a bit and made minor changes to the code comments.)
Per TDobes' comments:
* INSTALL.txt corrected to use 4.3.3, not 4.33.
* .htaccess: removed allow_call_time_pass_reference. two confirmations that a) the setting was wrong in the first place, b) there were no adverse affects for the incorrect setting, c) the PHP docs say it is deprecated.
* .htaccess: removed short_open_tag. Running grep -r "<? " * across the entire directory tree of both core and contributions only brought up contributions and no core. I agree that the fuller form is better. The following contributions will need to be updated: modules/edit_template/edit_template.module, sandbox/garym/themes/marvin_2k/templates/page.tpl.php, sandbox/killes/compare.php, sandbox/paolino/import/click.php, themes/spreadfirefox/block.tpl.php. For error's sake, I also did a manual verification for "<?" (no space) across core and came up against nothing in addition to the above contribs.
Per Goba's comments:
* .htaccess: Moved session.auto_start back.
* sites/default/settings.php: Removed track_vars.
Per mailing list comments:
* INSTALL.txt: Added text about the files/ directory, creating it, and permissions.
* INSTALL.txt: Added an example of why Drupal requires cron (the search.module) in an attempt to justify why a crontab is a good, nay, required step.
And my own further analities:
* .htaccess: cleaned up some whitespace valleys (i hate 'em, hate 'em!) and fixed a few stray colons.
* settings.php: minor whitespace error.
# The INSTALL.txt no longer contains the SERVER CONFIGURATION block. These settings are now hardcoded into sites/default/settings.php, and are merely scary technical junk here.
# The INSTALL.txt has been updated with the latest system requirements. A whole sentence was struck regarding differing versions of PHP for the OSs.
# The INSTALL.txt contains URLs to MySQL and PostgreSQL. If we're including the URL for PHP in the same sentence, then there's no reason why we wouldn't include them for the database engines. What are the minimal requirements for the RDBMS? Those should be included here too.
# The INSTALL.txt's OPTIONAL COMPONENTS has renamed to OPTIONAL REQUIREMENTS. The only difference between the meaning is the amount of user confusion.
# The INSTALL.txt has a new CONTENTS OF THIS FILE, in hopes that people will more immediately notice that there are upgrade instructions at the bottom.
# The INSTALL.txt had some potentially confusing lines adjusted, including further clarifications, standarding to "userid" (instead of using both userid and username interchangebly) and so on.
# I've moved most of .htaccess php_value's to the ini_set system for /sites/. There are a few reasons for this, chiefly that it is centralizing all the PHP setting modifications to one place. But, this also clears up a few initial configuration issues: first, the user doesn't have to worry about whether they have Apache 1 or 2, and whether they need to change an IfModule line. Also, the running assumption is that these php_value's are /going to work by default anyways/, when the INSTALL.txt suggests otherwise (under OPTIONAL REQUIREMENTS, it talks about "the ability to use local .htaccess files", which suggests that "local .htaccess files" INCLUDING "mod_rewrite" are entirely optional.) Some variables, however, had to remain in .htaccess because they can't be overridden at runtime, but the amount was so small that duplicating them for both Apache 1 and Apache 2 possibilities is no longer a prohibitive concern.
# There are two variables in .htaccess that I'm concerned about: track_vars, and allow_call_time_pass_reference. track_vars appears to be no longer necessary (as of 4.0.3, track_vars is always on, and my setting it here had no impact on the results of a phpinfo), and allow_call_time_pass_reference seems, at least here, to ONLY WORK if the .htaccess value is set to "1", and not "On" - meaning that Drupal installations are currently working correctly with its default value (off). According to the PHP docs, this feature is now deprecated. However, since both of these variables require further investigation, track_vars has been moved to settings.php, and allow_call_time_pass_reference has been "fixed" to a 1 (not 'On').
# Along with the changes above for sites/default/settings.php, I've also removed the spacing indent in the documentation, as well as many a few grammatical/punctuation changes here and there. I don't think the leading spacing is "right" according to the style guidelines, but maybe there's a special need for it. Correct me if I'm wrong.
Dries Buytaert
Steven Wittens