[Koha-patches] [PATCH] Bug 8089: Cache sysprefs with Koha::Cache::Object

[Jared Camins-Esakov]

This patch replaces the %sysprefs hash variable with a
Koha::Cache::Object-tied hash that allows the user to cache sysprefs
in memcached, fastmmap, or memory.

To test:
1) Enable the cache as described on bug 9434.
2) Try viewing some pages in the OPAC and staff client. If the syspref
   caching isn't working, you'll be redirected to the web installer
   (in the staff client) or be shown the maintenance page (in the OPAC).
3) Disable the cache by unsetting the CACHING_SYSTEM environment
   variable.
4) Try viewing some pages in the OPAC and staff client. If the syspref
   caching isn't working, you'll be redirected to the web installer
   (in the staff client) or be shown the maintenance page (in the OPAC).

Note that this will not improve performance. It does, however, eliminate
the problem of sysprefs not getting updated in all threads in
multi-threaded environments.
---
 C4/Context.pm |   66 +++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 48 insertions(+), 18 deletions(-)

diff --git a/C4/Context.pm b/C4/Context.pm
index 4e6c5fb..c66b22d 100644
--- a/C4/Context.pm
+++ b/C4/Context.pm
@@ -19,6 +19,8 @@ package C4::Context;
 use strict;
 use warnings;
 use vars qw($VERSION $AUTOLOAD $context @context_stack $servers $memcached $ismemcached);
+use Koha::Cache;
+use Carp;
 
 BEGIN {
 	if ($ENV{'HTTP_USER_AGENT'})	{
@@ -534,28 +536,55 @@ with this method.
 # FIXME: running this under mod_perl will require a means of
 # flushing the caching mechanism.
 
-my %sysprefs;
+my $sysprefs;
 my $use_syspref_cache = 1;
+my $cache;
 
 sub preference {
     my $self = shift;
     my $var  = lc(shift);                          # The system preference to return
 
-    if ($use_syspref_cache && exists $sysprefs{$var}) {
-        return $sysprefs{$var};
+    unless (defined $sysprefs) {
+        unless ($cache) {
+            $cache = Koha::Cache->new();
+        }
+        $sysprefs = $cache->create_hash(
+            {
+                'key'         => 'syspref',
+                'allowupdate' => 1,
+                'cache_type' => $use_syspref_cache ? '' : 'null',
+                'preload'     => sub {
+                    my $dbh      = C4::Context->dbh or return {};
+                    my $vars = $dbh->selectall_arrayref("SELECT variable, value FROM systempreferences");
+                    my %sysprefs = ();
+                    foreach my $row (@$vars) {
+                        $sysprefs{$row->[0]} = $row->[1];
+                    }
+                    return \%sysprefs;
+                },
+                'constructor' => sub {
+
+                    # Look up systempreferences.variable==$var
+                    my $var      = pop;
+                    my $sysprefs = pop || {};
+                    my $dbh      = C4::Context->dbh or return 0;
+                    my $sql =
+"SELECT value FROM systempreferences WHERE variable=? LIMIT 1";
+                    $ENV{DEBUG} && carp "Retrieving syspref $var from database";
+                    my $sth = $dbh->prepare_cached($sql);
+                    $sth->execute($var);
+                    my $res = $sth->fetchrow_hashref;
+                    if ($res && $res->{'value'}) {
+                        $sysprefs->{$var} = $res->{'value'};
+                    } else {
+                        $sysprefs->{$var} = '';
+                    }
+                    return $sysprefs;
+                },
+            }
+        );
     }
-
-    my $dbh  = C4::Context->dbh or return 0;
-
-    # Look up systempreferences.variable==$var
-    my $sql = <<'END_SQL';
-        SELECT    value
-        FROM    systempreferences
-        WHERE    variable=?
-        LIMIT    1
-END_SQL
-    $sysprefs{$var} = $dbh->selectrow_array( $sql, {}, $var );
-    return $sysprefs{$var};
+    return $sysprefs->{$var};
 }
 
 sub boolean_preference {
@@ -591,7 +620,7 @@ used with Plack and other persistent environments.
 sub disable_syspref_cache {
     my ($self) = @_;
     $use_syspref_cache = 0;
-    $self->clear_syspref_cache();
+    $self->clear_syspref_cache() if defined($sysprefs);
 }
 
 =head2 clear_syspref_cache
@@ -605,7 +634,8 @@ will not be seen by this process.
 =cut
 
 sub clear_syspref_cache {
-    %sysprefs = ();
+    %{$sysprefs} = ();
+    return;
 }
 
 =head2 set_preference
@@ -636,7 +666,7 @@ sub set_preference {
     " );
 
     if($sth->execute( $var, $value )) {
-        $sysprefs{$var} = $value;
+        $sysprefs->{$var} = $value;
     }
     $sth->finish;
 }
-- 
1.7.9.5