From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jakub Narebski Subject: [RFC PATCHv2 05/10] gitweb/cache.pm - Adaptive cache expiration time Date: Tue, 9 Feb 2010 11:30:22 +0100 Message-ID: <1265711427-15193-6-git-send-email-jnareb@gmail.com> References: <1265711427-15193-1-git-send-email-jnareb@gmail.com> Cc: John 'Warthog9' Hawley , John 'Warthog9' Hawley , Petr Baudis , Jakub Narebski To: git@vger.kernel.org X-From: git-owner@vger.kernel.org Tue Feb 09 11:31:12 2010 Return-path: Envelope-to: gcvg-git-2@lo.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1NenN9-0003mJ-Qi for gcvg-git-2@lo.gmane.org; Tue, 09 Feb 2010 11:31:12 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753799Ab0BIKa5 (ORCPT ); Tue, 9 Feb 2010 05:30:57 -0500 Received: from fg-out-1718.google.com ([72.14.220.157]:35227 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753868Ab0BIKau (ORCPT ); Tue, 9 Feb 2010 05:30:50 -0500 Received: by fg-out-1718.google.com with SMTP id 19so19836fgg.1 for ; Tue, 09 Feb 2010 02:30:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:from:to:cc:subject:date :message-id:x-mailer:in-reply-to:references; bh=BOlLJju6lb75+ZTmU0Z02D1JTUF9x81xNS36ptSFNKU=; b=TmPDk82Ml5NeKJbURsqta2AGxtjMgjkxzXQyQnjK6Q16Oo3qwjqFCzJa6aTzQItosJ 8B+7IctsAI1q4mA7SJuMzrXibv6maiVn0ZIfwPvCOhKaXhO2+xpoO/xeg7nzFAS3cUtZ JXS9cCCoFCD0F02epfn9afNLlCEf2dWedZt7E= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=jQhh6NQzmy0fX/dNUhqrAAUwZ1Nps3ZgLW8FWbGA8SMnArPJ32KALJoy4YRjJXwjTy 3tNqgW+NY6UV4trtI8m7NjZrMv2M7JBPTo3SjO7MMqcY3h1owwCv/D9xvEIdTAJO++xs 0Ue4vkCYZT9zAVuWE8xbUXWf73oAYVLKAoj+M= Received: by 10.87.69.33 with SMTP id w33mr11080076fgk.29.1265711447778; Tue, 09 Feb 2010 02:30:47 -0800 (PST) Received: from localhost.localdomain (abvg140.neoplus.adsl.tpnet.pl [83.8.204.140]) by mx.google.com with ESMTPS id 16sm2344332fxm.8.2010.02.09.02.30.46 (version=SSLv3 cipher=RC4-MD5); Tue, 09 Feb 2010 02:30:47 -0800 (PST) X-Mailer: git-send-email 1.6.6.1 In-Reply-To: <1265711427-15193-1-git-send-email-jnareb@gmail.com> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Add to GitwebCache::SimpleFileCache support for adaptive lifetime (cache expiration) control. Cache lifetime can be increased or decreased by any factor, e.g. load average, through the definition of the 'check_load' callback. Note that using ->set_expires_in, or unsetting 'check_load' via ->set_check_load(undef) turns off adaptive caching. Make gitweb automatically adjust cache lifetime by load, using get_loadavg() function. Define and describe default parameters for dynamic (adaptive) cache expiration time control. There are some very basic tests of dynamic expiration time in t9503, namely checking if dynamic expire time is within given upper and lower bounds. To be implemented (from original patch by J.H.): * optional locking interface, where only one process can update cache (using flock) * server-side progress indicator when waiting for filling cache, which in turn requires separating situations (like snapshots and other non-HTML responses) where we should not show 'please wait' message Inspired-by-code-by: John 'Warthog9' Hawley Signed-off-by: Jakub Narebski --- Differences from v1: * Proper commit message * Adaptive cache expiration can be configured in gitweb config file by changing 'expires_min', 'expires_max', 'increase_factor' in %cache_options. Those parameters are described in detail. * You can turn adaptive cache expiration by setting 'check_load' to undef. * By default adaptive cache expiration is turned off; there are extra check when to run 'check_load' subroutine. * Instead of removing ->set_expires_in(), it just sets 'expires_min' and 'expires_max' to the same value, which turns off adaptive expiration. * Test assertions for adaptive cache expiration: 'expires_min' <= $cache->get_expires_in() <= 'expires_max' Differences from relevant parts of J.H. patch: * 'increase_factor' is configurable rather than hardcoded * 'check_load' is passed via conctructor parameter; gitweb by default sets it to \&get_loadavg. This means that cache.pm is not entangled with gitweb, at least for this feature. * options are stored in %cache_options, e.g. as 'expires_max' (compatible with Cache::Adaptive), and not as global variables with un-Perlish camelCase names like $maxCacheTime. * API tests Possible improvements: * Turn off adaptive cache lifetime by unsetting check_load, and not only by using ->set_expires_in() gitweb/cache.pm | 55 +++++++++++++++++++++++++++++++++++--- gitweb/gitweb.perl | 27 +++++++++++++++++- t/t9503/test_cache_interface.pl | 22 +++++++++++++++ 3 files changed, 97 insertions(+), 7 deletions(-) diff --git a/gitweb/cache.pm b/gitweb/cache.pm index 64c333b..d81f6e8 100644 --- a/gitweb/cache.pm +++ b/gitweb/cache.pm @@ -63,7 +63,8 @@ sub new { my $self = {}; $self = bless($self, $class); - my ($root, $depth, $ns, $expires_in); + my ($root, $depth, $ns); + my ($expires_min, $expires_max, $increase_factor, $check_load); if (defined $p_options_hash_ref) { $root = $p_options_hash_ref->{'cache_root'} || @@ -72,19 +73,31 @@ sub new { $p_options_hash_ref->{'cache_depth'} || $p_options_hash_ref->{'depth'}; $ns = $p_options_hash_ref->{'namespace'}; - $expires_in = + $expires_min = + $p_options_hash_ref->{'expires_min'} || $p_options_hash_ref->{'default_expires_in'} || $p_options_hash_ref->{'expires_in'}; + $expires_max = + $p_options_hash_ref->{'expires_max'}; + $increase_factor = $p_options_hash_ref->{'expires_factor'}; + $check_load = $p_options_hash_ref->{'check_load'}; } $root = $DEFAULT_CACHE_ROOT unless defined($root); $depth = $DEFAULT_CACHE_DEPTH unless defined($depth); $ns = '' unless defined($ns); - $expires_in = -1 unless defined($expires_in); # <0 means never + $expires_min = 20 unless defined($expires_min); + $expires_max = $expires_min + if (!defined($expires_max) && exists $p_options_hash_ref->{'expires_in'}); + $expires_max = 1200 unless (defined($expires_max)); + $increase_factor = 60 unless defined($increase_factor); $self->set_root($root); $self->set_depth($depth); $self->set_namespace($ns); - $self->set_expires_in($expires_in); + $self->set_expires_min($expires_min); + $self->set_expires_max($expires_max); + $self->set_increase_factor($increase_factor); + $self->set_check_load($check_load); return $self; } @@ -94,7 +107,7 @@ sub new { # http://perldesignpatterns.com/perldesignpatterns.html#AccessorPattern -foreach my $i (qw(depth root namespace expires_in)) { +foreach my $i (qw(depth root namespace expires_min expires_max increase_factor check_load)) { my $field = $i; no strict 'refs'; *{"get_$field"} = sub { @@ -107,6 +120,38 @@ foreach my $i (qw(depth root namespace expires_in)) { }; } +# ...................................................................... +# pseudo-accessors + +sub get_expires_in { + my ($self) = @_; + + # short-circuit + if (!defined $self->get_check_load() || + $self->get_expires_max() <= $self->get_expires_min()) { + return $self->get_expires_min(); + } + + my $expires_in = + #$self->get_expires_min() + + $self->get_increase_factor() * $self->get_check_load()->(); + + if ($expires_in < $self->get_expires_min()) { + return $self->get_expires_min(); + } elsif ($expires_in > $self->get_expires_max()) { + return $self->get_expires_max(); + } + + return $expires_in; +} + +sub set_expires_in { + my ($self, $duration) = @_; + + $self->set_expires_min($duration); + $self->set_expires_max($duration); +} + # ---------------------------------------------------------------------- # utility functions and methods diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl index f02ead9..aabed72 100755 --- a/gitweb/gitweb.perl +++ b/gitweb/gitweb.perl @@ -255,13 +255,36 @@ our %cache_options = ( # * File::Spec->catdir(File::Spec->tmpdir(), 'gitweb-cache'), # * '/var/cache/gitweb' (FHS compliant, requires being set up), 'cache_root' => 'cache', + # The number of subdirectories deep to cache object item. This should be # large enough that no cache directory has more than a few hundred # objects. Each non-leaf directory contains up to 256 subdirectories # (00-ff). Must be larger than 0. 'cache_depth' => 1, - # The (global) expiration time for objects placed in the cache, in seconds. - 'expires_in' => 20, + + # The (global) minimum expiration time for objects placed in the cache, + # in seconds. If the dynamic adaptive cache exporation time is lower + # than this number, we set cache timeout to this minimum. + 'expires_min' => 20, # 20 seconds + + # The (global) maximum expiration time for dynamic (adaptive) caching + # algorithm, in seconds. If the adaptive cache lifetime exceeds this + # number, we set cache timeout to this maximum. + # (If 'expires_min' >= 'expires_max', there is no adaptive cache timeout, + # and 'expires_min' is used as expiration time for objects in cache.) + 'expires_max' => 1200, # 20 minutes + + # Cache lifetime will be increased by applying this factor to the result + # from 'check_load' callback (see below). + 'expires_factor' => 60, # expire time in seconds for 1.0 (100% CPU) load + + # User supplied callback for deciding the cache policy, usually system + # load. Multiplied by 'expires_factor' gives adaptive expiration time, + # in seconds, subject to the limits imposed by 'expires_min' and + # 'expires_max' bounds. Set to undef (or delete) to turn off dynamic + # lifetime control. + # (Compatibile with Cache::Adaptive.) + 'check_load' => \&get_loadavg, ); diff --git a/t/t9503/test_cache_interface.pl b/t/t9503/test_cache_interface.pl index 42c49e9..3945adc 100755 --- a/t/t9503/test_cache_interface.pl +++ b/t/t9503/test_cache_interface.pl @@ -118,6 +118,28 @@ $cache->set($key, $value); ok(!defined($cache->get($key)), 'cache is expired'); $cache->set_expires_in(-1); +# Test assertions for adaptive cache expiration +# +my $load = 0.0; +sub load { return $load; } +my $expires_min = 10; +my $expires_max = 30; +$cache->set_expires_min($expires_min); +$cache->set_expires_max($expires_max); +$cache->set_check_load(\&load); +cmp_ok($cache->get_expires_min(), '==', $expires_min, '"expires min" set correctly'); +cmp_ok($cache->get_expires_max(), '==', $expires_max, '"expires max" set correctly'); +cmp_ok($cache->get_expires_in(), '>=', $expires_min, + '"expires in" bound from down for load=0'); +cmp_ok($cache->get_expires_in(), '<=', $expires_max, + '"expires in" bound from up for load=0'); +$load = 1_000; +cmp_ok($cache->get_expires_in(), '>=', $expires_min, + '"expires in" bound from down for heavy load'); +cmp_ok($cache->get_expires_in(), '<=', $expires_max, + '"expires in" bound from up for heavy load'); +$cache->set_expires_in(-1); + # ...................................................................... # Prepare for testing cache_fetch from $cache_pm -- 1.6.6.1