Subject: Re: [PATCH] gitweb: Support caching projects list

From: Jakub Narebski <[email-masked]>
Date: Sat, 15 Mar 2008 14:44:42 -0700 (PDT)

Petr Baudis <[email-masked]> writes:

> On repo.or.cz (permanently I/O overloaded and hosting 1050 project +
> forks), 

It looks like repo.or.cz is overwhelmed by its success. I hope that
now that there are other software hosting sites with git hosting
(Savannah, GitHub, Gitorious,...) the number of projects wouldn't grow
as rapidly.

> the projects list (the default gitweb page) can take more than
> a minute to generate. This naive patch adds simple support for caching
> the projects list data structure so that all the projects do not need
> to get rescanned at every page access.

Another solution would be to divide projects list page into pages,
perhaps adding search box for searching for a project (by name, by
description and by owner).

Nevertheless even with pagination, if we want to have "sort by last
update" we do need caching.

[...]
> +# projects list cache for busy sites with many projects;
> +# if you set this to non-zero, it will be used as the cached
> +# index lifetime in minutes
> +# the cached list version is stored in /tmp and can be tweaked
> +# by other scripts running with the same uid as gitweb - use this
> +# only at secure installations; only single gitweb project root per
> +# system is supported!
> +our $projlist_cache_lifetime = 0;

[...]
> +sub git_project_list_body {
[...]
> +	my $cache_file = '/tmp/gitweb.index.cache';
> +	use File::stat;
> +
> +	my @projects;
> +	my $stale = 0;
> +	if ($cache_lifetime and -f $cache_file
> +	    and stat($cache_file)->mtime + $cache_lifetime * 60 > time()
> +	    and open (my $fd, $cache_file)) {
> +		$stale = time() - stat($cache_file)->mtime;
> +		my @dump = <$fd>;
> +		close $fd;
> +		# Hack zone start
> +		my $VAR1;
> +		eval join("\n", @dump);
> +		@projects = @$VAR1;
> +		# Hack zone end
> +	} else {
> +		if ($cache_lifetime and -f $cache_file) {
> +			# Postpone timeout by two minutes so that we get
> +			# enough time to do our job.
> +			my $time = time() - $cache_lifetime + 120;
> +			utime $time, $time, $cache_file;
> +		}
> +		@projects = git_get_projects_details($projlist, $check_forks);
> +		if ($cache_lifetime and open (my $fd, '>'.$cache_file)) {
> +			use Data::Dumper;
> +			print $fd Dumper(\@projects);
> +			close $fd;
> +		}
> +	}

This could be much simplified with perl-cache (perl-Cache-Cache).
Unfortunately this is non-standard module, not distributed (yet?)
with Perl.

Warning: not tested in gitweb!

+	use Cache::FileCache;
+
+	my $cache;
+	my $projects;
+	
+	if ($cache_lifetime) {
+		$cache = new Cache::FileCache(
+			{ namespace => 'gitweb',
+			  default_expires_in => $cache_lifetime
+			});
+		$projects = $cache->get('projects_list');
+	}
+	if (!defined $projects) {
+		$projects = [ git_get_projects_details($projlist, $check_forks); ];
+		$cache->set('projects_list', $projects)
+			if defined $cache;
+	}

-- 
Jakub Narebski
Poland
ShadeHawk on #git