Add locking for indexer-based notifications

inc/subscription.php

@@ -9,6 +9,8 @@
  * - subscription_set
  * - get_info_subscribed
  * - subscription_addresslist
+ * - subscription_lock
+ * - subscription_unlock
  *
  * @author  Adrian Lang <lang@cosmocode.de>
  * @license GPL 2 (http://www.gnu.org/licenses/gpl.html)
@@ -36,6 +38,32 @@ function subscription_filename($id) {
     return metaFN($meta_froot, $meta_fname);
 }
 
+/**
+ * Lock subscription info for an ID
+ *
+ * @param string $id The target page or namespace, specified by id; Namespaces
+ *                   are identified by appending a colon.
+ *
+ * @author Adrian Lang <lang@cosmocode.de>
+ */
+function subscription_lock($id) {
+    $lockf = subscription_filename($id) . '.lock';
+    return !file_exists($lockf) && touch($lockf);
+}
+
+/**
+ * Unlock subscription info for an ID
+ *
+ * @param string $id The target page or namespace, specified by id; Namespaces
+ *                   are identified by appending a colon.
+ *
+ * @author Adrian Lang <lang@cosmocode.de>
+ */
+function subscription_unlock($id) {
+    $lockf = subscription_filename($id) . '.lock';
+    return file_exists($lockf) && unlink($lockf);
+}
+
 /**
  * Set subscription information
  *

lib/exe/indexer.php

@@ -353,6 +353,9 @@ function sendDigest() {
     $olduser  = $_SERVER['REMOTE_USER'];
 
     foreach($subscriptions as $id => $users) {
+        if (!subscription_lock($id)) {
+            continue;
+        }
         foreach($users as $data) {
             list($user, $style, $lastupdate) = $data;
             $lastupdate = (int) $lastupdate;
@@ -399,6 +402,7 @@ function sendDigest() {
             // Update notification time.
             subscription_set($user, $id, $style, time(), true);
         }
+        subscription_unlock($id);
     }
 
     // restore current user info