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 <warthog9@xxxxxxxxxx>
Signed-off-by: Jakub Narebski <jnareb@xxxxxxxxx>
---
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
--
To unsubscribe from this list: send the line "unsubscribe git" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html