- Patch #314358 by wonder95, Crell, killes, et al: add option to ignore slave servers. Finally.

4 files changed, 48 insertions, 0 deletions

diff --git a/includes/database/database.inc b/includes/database/database.inc
index 44a90c1ee..45f4d748c 100644
--- a/includes/database/database.inc
+++ b/includes/database/database.inc
@@ -2687,6 +2687,19 @@ function db_rewrite_sql($query, $primary_table = 'n', $primary_field = 'nid',  $
   return $query;
 }
 
+/**
+ * Helper function to get duration lag from variable
+ * and set the session variable that contains the lag.
+ */
+function db_ignore_slave() {
+  // Five minutes is long enough to allow the slave to break and resume
+  // interrupted replication without causing problems on the Drupal site
+  // from the old data.
+  $duration = variable_get('maximum_replication_lag', 300);
+  
+  // Set session variable with amount of time to delay  before using slave.
+  $_SESSION['ignore_slave_server'] = REQUEST_TIME + $duration;
+}
 
 /**
  * @} End of "ingroup database-legacy".
diff --git a/modules/comment/comment.module b/modules/comment/comment.module
index 7b6180f20..bc578e350 100644
--- a/modules/comment/comment.module
+++ b/modules/comment/comment.module
@@ -962,12 +962,19 @@ function comment_save(&$comment) {
         'homepage' => $comment['homepage'],
       ))
       ->execute();
+      
+    // Ignore slave server temporarily to give time for the
+    // saved node to be propagated to the slave.
+    db_ignore_slave();
+   
     // Tell the other modules a new comment has been submitted.
     comment_invoke_comment($comment, 'insert');
+    
     // Add an entry to the watchdog log.
     watchdog('content', 'Comment: added %subject.', array('%subject' => $comment['subject']), WATCHDOG_NOTICE, l(t('view'), 'comment/' . $comment['cid'], array('fragment' => 'comment-' . $comment['cid'])));
   }
   _comment_update_node_statistics($comment['nid']);
+  
   // Clear the cache so an anonymous user can see his comment being added.
   cache_clear_all();
 
diff --git a/modules/node/node.module b/modules/node/node.module
index 6692a20de..9eec39e11 100644
--- a/modules/node/node.module
+++ b/modules/node/node.module
@@ -1003,6 +1003,10 @@ function node_save($node) {
 
   // Clear the page and block caches.
   cache_clear_all();
+
+  // Ignore slave server temporarily to give time for the
+  // saved node to be propagated to the slave.
+  db_ignore_slave();
 }
 
 /**
diff --git a/modules/system/system.module b/modules/system/system.module
index 7a2667457..567cf8989 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -872,8 +872,32 @@ function system_init() {
   drupal_add_css(drupal_get_path('module', 'system') . '/defaults.css');
   drupal_add_css(drupal_get_path('module', 'system') . '/system.css');
   drupal_add_css(drupal_get_path('module', 'system') . '/system-menus.css');
+
+
+  // Ignore slave database servers for this request.
+  //
+  // In Drupal's distributed database structure, new data is written to the master
+  // and then propagated to the slave servers.  This means there is a lag
+  // between when data is written to the master and when it is available on the slave.
+  // At these times, we will want to avoid using a slave server temporarily.
+  // For example, if a user posts a new node then we want to disable the slave
+  // server for that user temporarily to allow the slave server to catch up.
+  // That way, that user will see their changes immediately while for other
+  // users we still get the benefits of having a slave server, just with slightly
+  // stale data.  Code that wants to disable the slave server should use the 
+  // db_set_ignore_slave() function to set $_SESSION['ignore_slave_server'] to 
+  // the timestamp after which the slave can be re-enabled.
+  if (isset($_SESSION['ignore_slave_server'])) {
+    if ($_SESSION['ignore_slave_server'] >= REQUEST_TIME) {
+      Database::ignoreTarget('default', 'slave');
+    }
+    else {
+      unset($_SESSION['ignore_slave_server']);
+    }
+  }
 }
 
+
 /**
  * Implement MODULE_preprocess_HOOK().
  */