From: John Napiorkowski <jjn1056@yahoo.com>
Date: Mon, 15 Dec 2008 22:02:19 +0000 (+0000)
Subject: changes to replication so that if a replicant is offline when we do the initial conne... 
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=f15afa13598dd767ba9547328a31d4b98313a896;p=dbsrgits%2FDBIx-Class-Historic.git

changes to replication so that if a replicant is offline when we do the initial connection (or if we need to globally reconnect later) the connection does not die.  This is different from when a replicant is available just not listening, or if the replicant is too laggy.  Thanks David Steinbrunner for the patch suggestions.
---

diff --git a/lib/DBIx/Class/Storage/DBI/Replicated/Pool.pm b/lib/DBIx/Class/Storage/DBI/Replicated/Pool.pm
index b1cdc82..a3db265 100644
--- a/lib/DBIx/Class/Storage/DBI/Replicated/Pool.pm
+++ b/lib/DBIx/Class/Storage/DBI/Replicated/Pool.pm
@@ -168,14 +168,31 @@ and return it.
 sub connect_replicant {
   my ($self, $schema, $connect_info) = @_;
   my $replicant = $self->create_replicant($schema);
-    
-  $replicant->connect_info($connect_info);    
-  $replicant->ensure_connected;
-  DBIx::Class::Storage::DBI::Replicated::Replicant->meta->apply($replicant);
-    
+  $replicant->connect_info($connect_info);
+  $self->_safely_ensure_connected($replicant);
+  DBIx::Class::Storage::DBI::Replicated::Replicant->meta->apply($replicant);  
   return $replicant;
 }
 
+=head2 _safely_ensure_connected ($replicant)
+
+The standard ensure_connected method with throw an exception should it fail to
+connect.  For the master database this is desirable, but since replicants are
+allowed to fail, this behavior is not desirable.  This method wraps the call
+to ensure_connected in an eval in order to catch any generated errors.  That
+way a slave to go completely offline (ie, the box itself can die) without
+bringing down your entire pool of databases.
+
+=cut
+
+sub _safely_ensure_connected {
+  my ($self, $replicant, @args) = @_;
+  my $return; eval {
+    $return = $replicant->ensure_connected(@args);
+  };  
+  return $return;
+}
+
 =head2 connected_replicants
 
 Returns true if there are connected replicants.  Actually is overloaded to
@@ -248,9 +265,9 @@ sub validate_replicants {
   my $self = shift @_;
   foreach my $replicant($self->all_replicants) {
     if(
+      $self->_safely_ensure_connected($replicant) &&  
       $replicant->is_replicating &&
-      $replicant->lag_behind_master <= $self->maximum_lag &&
-      $replicant->ensure_connected
+      $replicant->lag_behind_master <= $self->maximum_lag
     ) {
       $replicant->active(1)
     } else {
diff --git a/lib/DBIx/Class/Storage/DBI/Replicated/Replicant.pm b/lib/DBIx/Class/Storage/DBI/Replicated/Replicant.pm
index d97120b..e9612f3 100644
--- a/lib/DBIx/Class/Storage/DBI/Replicated/Replicant.pm
+++ b/lib/DBIx/Class/Storage/DBI/Replicated/Replicant.pm
@@ -52,7 +52,7 @@ has 'active' => (
 
 This class defines the following methods.
 
-=head2 after: _query_start
+=head2 around: _query_start
 
 advice iof the _query_start method to add more debuggin
 
diff --git a/t/93storage_replication.t b/t/93storage_replication.t
index ab2ffe4..161013b 100644
--- a/t/93storage_replication.t
+++ b/t/93storage_replication.t
@@ -249,6 +249,7 @@ $replicated
 $replicated->replicate;
 $replicated->schema->storage->replicants->{$replicant_names[0]}->active(1);
 $replicated->schema->storage->replicants->{$replicant_names[1]}->active(1);
+$replicated->schema->storage->pool->validate_replicants;
 
 ## Make sure we can read the data.
 
@@ -355,6 +356,7 @@ ok $replicated->schema->resultset('Artist')->find(2)
 
 $replicated->schema->storage->replicants->{$replicant_names[0]}->active(1);
 $replicated->schema->storage->replicants->{$replicant_names[1]}->active(1);
+$replicated->schema->storage->pool->validate_replicants;
 
 ok $replicated->schema->resultset('Artist')->find(2)
     => 'Returned to replicates';