#58: added lock for cron triggers

CRM/Civirules/Trigger/Cron.php

@@ -2,6 +2,11 @@
 
 abstract class CRM_Civirules_Trigger_Cron extends CRM_Civirules_Trigger {
 
+  /**
+   * @var \CRM_Core_Lock
+   */
+  private $lock;
+
   /**
    * This function returns a CRM_Civirules_TriggerData_TriggerData this entity is used for triggering the rule
    *
@@ -12,11 +17,19 @@ abstract class CRM_Civirules_Trigger_Cron extends CRM_Civirules_Trigger {
   abstract protected function getNextEntityTriggerData();
 
   /**
-   * @return int
+   * @return array
    */
   public function process() {
     $count = 0;
     $isValidCount = 0;
+
+    if (!$this->acquireLock()) {
+      return array(
+        'count' => $count,
+        'is_valid_count' => $isValidCount,
+      );
+    }
+
     while($triggerData = $this->getNextEntityTriggerData()) {
       $this->alterTriggerData($triggerData);
       $isValid = CRM_Civirules_Engine::triggerRule($this, $triggerData);
@@ -25,11 +38,57 @@ abstract class CRM_Civirules_Trigger_Cron extends CRM_Civirules_Trigger {
       }
       $count ++;
     }
+
+    $this->acquireLock();
+
     return array(
       'count' => $count,
       'is_valid_count' => $isValidCount,
     );
   }
 
+  /**
+   * Acquires a lock. Returns true when the lock was free and is acquired
+   * Returns false when the lock was not free or could not be acquired.
+   *
+   * @return bool
+   */
+  protected function acquireLock() {
+    try {
+      $name = 'civirules_cron_rule_' . $this->getRuleId();
+      if ($this->lock == NULL) {
+        $this->lock = new CRM_Core_Lock($name, $this->getLockTimeout());
+        if ($this->lock->isFree()) {
+          $this->lock->acquire();
+          if ($this->lock->isAcquired()) {
+            return TRUE;
+          }
+        }
+      }
+    } catch (\CRM_Core_Exception $e) {
+      // Do nothing.
+    }
+    return FALSE;
+  }
+
+  /**
+   * Releases the lock
+   *
+   */
+  protected function releaseLock() {
+    if ($this->lock) {
+      $this->lock->release();
+    }
+  }
+
+  /**
+   * Returns the lock timeout for this trigger in seconds
+   *
+   * @return int
+   */
+  protected function getLockTimeout() {
+    return 900; //900 seconds = 15 minutes
+  }
+
 
-}
\ No newline at end of file
+}