From 6070312284b85e48cd75ecbf24fd00fa2e77a499 Mon Sep 17 00:00:00 2001
From: Jared Camins-Esakov <jcamins@cpbibliography.com>
Date: Thu, 1 Nov 2012 14:46:57 -0400
Subject: [PATCH] Bug 9005: Allow user to disable syspref cache

Because C4::Context uses an in-memory hash for caching sysprefs,
changing a syspref under a multi-threaded persistent environment
requires a server restart. This patch makes it possible disable
the syspref cache.

To test:
1) If you are using a multi-threaded persistent server (Starman, etc.),
   change a syspref and note that the effects of the syspref change may
   or may not be visible on any given request before applying this patch.
   You will need to choose a syspref with obvious effects that can be
   seen by simply refreshing the page. I recommend enabling or
   disabling additional languages in the OPAC, since you can refresh the
   page a dozen times and reasonably expect to see the new behavior you
   set only 1/n of the time.
2) Apply patch.
3) Add "C4::Context->disable_syspref_cache();" to your koha.psgi file
4) Repeat step 1, noting that you never see the stale behavior.
5) Run test at t/db_dependent/Context.t.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
All tests passed.

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
---
 C4/Context.pm            |   32 ++++++++++++++++++++++++-
 t/db_dependent/Context.t |   60 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/C4/Context.pm b/C4/Context.pm
index e785002..7de3f94 100644
--- a/C4/Context.pm
+++ b/C4/Context.pm
@@ -523,12 +523,13 @@ with this method.
 # flushing the caching mechanism.
 
 my %sysprefs;
+my $use_syspref_cache = 1;
 
 sub preference {
     my $self = shift;
     my $var  = lc(shift);                          # The system preference to return
 
-    if (exists $sysprefs{$var}) {
+    if ($use_syspref_cache && exists $sysprefs{$var}) {
         return $sysprefs{$var};
     }
 
@@ -552,6 +553,35 @@ sub boolean_preference {
     return defined($it)? C4::Boolean::true_p($it): undef;
 }
 
+=head2 enable_syspref_cache
+
+  C4::Context->enable_syspref_cache();
+
+Enable the in-memory syspref cache used by C4::Context. This is the
+default behavior.
+
+=cut
+
+sub enable_syspref_cache {
+    my ($self) = @_;
+    $use_syspref_cache = 1;
+}
+
+=head2 disable_syspref_cache
+
+  C4::Context->disable_syspref_cache();
+
+Disable the in-memory syspref cache used by C4::Context. This should be
+used with Plack and other persistent environments.
+
+=cut
+
+sub disable_syspref_cache {
+    my ($self) = @_;
+    $use_syspref_cache = 0;
+    $self->clear_syspref_cache();
+}
+
 =head2 clear_syspref_cache
 
   C4::Context->clear_syspref_cache();
diff --git a/t/db_dependent/Context.t b/t/db_dependent/Context.t
index eac3265..5105e84 100755
--- a/t/db_dependent/Context.t
+++ b/t/db_dependent/Context.t
@@ -5,6 +5,7 @@ use strict;
 use warnings;
 
 use Test::More;
+use Test::MockModule;
 use vars qw($debug $koha $dbh $config $ret);
 
 BEGIN {
@@ -42,6 +43,65 @@ foreach (grep {defined $koha->{$_}} sort @keys) {
 }
 ok($config = $koha->{config}, 'Getting $koha->{config} ');
 
+diag "Testing syspref caching.";
+
+my $dbh = C4::Context->dbh;
+$dbh->disconnect;
+
+my $module = new Test::MockModule('C4::Context');
+$module->mock(
+    '_new_dbh',
+    sub {
+        my $dbh = DBI->connect( 'DBI:Mock:', '', '' )
+          || die "Cannot create handle: $DBI::errstr\n";
+        return $dbh;
+    }
+);
+
+my $history;
+$dbh = C4::Context->dbh;
+
+$dbh->{mock_add_resultset} = [ ['value'], ['thing1'] ];
+$dbh->{mock_add_resultset} = [ ['value'], ['thing2'] ];
+$dbh->{mock_add_resultset} = [ ['value'], ['thing3'] ];
+$dbh->{mock_add_resultset} = [ ['value'], ['thing4'] ];
+
+is(C4::Context->preference("SillyPreference"), 'thing1', "Retrieved syspref (value='thing1') successfully with default behavior");
+$history = $dbh->{mock_all_history};
+is(scalar(@{$history}), 1, 'Retrieved syspref from database');
+
+$dbh->{mock_clear_history} = 1;
+is(C4::Context->preference("SillyPreference"), 'thing1', "Retrieved syspref (value='thing1') successfully with default behavior");
+$history = $dbh->{mock_all_history};
+is(scalar(@{$history}), 0, 'Did not retrieve syspref from database');
+
+C4::Context->disable_syspref_cache();
+is(C4::Context->preference("SillyPreference"), 'thing2', "Retrieved syspref (value='thing2') successfully with disabled cache");
+$history = $dbh->{mock_all_history};
+is(scalar(@{$history}), 1, 'Retrieved syspref from database');
+
+$dbh->{mock_clear_history} = 1;
+is(C4::Context->preference("SillyPreference"), 'thing3', "Retrieved syspref (value='thing3') successfully with disabled cache");
+$history = $dbh->{mock_all_history};
+is(scalar(@{$history}), 1, 'Retrieved syspref from database');
+
+C4::Context->enable_syspref_cache();
+$dbh->{mock_clear_history} = 1;
+is(C4::Context->preference("SillyPreference"), 'thing3', "Retrieved syspref (value='thing3') successfully from cache");
+$history = $dbh->{mock_all_history};
+is(scalar(@{$history}), 0, 'Did not retrieve syspref from database');
+
+C4::Context->clear_syspref_cache();
+$dbh->{mock_clear_history} = 1;
+is(C4::Context->preference("SillyPreference"), 'thing4', "Retrieved syspref (value='thing4') successfully after clearing cache");
+$history = $dbh->{mock_all_history};
+is(scalar(@{$history}), 1, 'Retrieved syspref from database');
+
+$dbh->{mock_clear_history} = 1;
+is(C4::Context->preference("SillyPreference"), 'thing4', "Retrieved syspref (value='thing4') successfully from cache");
+$history = $dbh->{mock_all_history};
+is(scalar(@{$history}), 0, 'Did not retrieve syspref from database');
+
 done_testing();
 
 1;
-- 
1.7.9.5