diff --git a/admin/include/functions.php b/admin/include/functions.php
index dee2a9a69..0c7813e97 100644
--- a/admin/include/functions.php
+++ b/admin/include/functions.php
@@ -2228,7 +2228,9 @@ function pwg_URL()
  */
 function invalidate_user_cache($full = true)
 {
-  global $persistent_cache;
+  global $persistent_cache, $logger;
+
+  $logger->info(__FUNCTION__.' starts');
 
   if ($full)
   {
@@ -2249,6 +2251,7 @@ UPDATE '.USER_CACHE_TABLE.'
   $persistent_cache->purge(true);
   conf_delete_param('count_orphans');
   trigger_notify('invalidate_user_cache', $full);
+  $logger->info(__FUNCTION__.' ends');
 }
 
 /**
diff --git a/include/Logger.class.php b/include/Logger.class.php
index 4c3785d2a..e2afa80ff 100644
--- a/include/Logger.class.php
+++ b/include/Logger.class.php
@@ -340,11 +340,13 @@ class Logger
    */
   private function formatMessage($level, $message, $cat, $context)
   {
+    global $page;
+
     if (!empty($context))
     {
       $message.= "\n" . $this->indent($this->contextToString($context));
     }
-    $line = "[" . $this->getTimestamp() . "]\t[" . self::levelToCode($level) . "]\t";
+    $line = "[" . $this->getTimestamp() . '][exec='.($page['execution_uuid']??'unkonwn')."]\t[" . self::levelToCode($level) . "]\t";
     if ($cat != null)
     {
       $line.= "[" . $cat . "]\t";
diff --git a/include/common.inc.php b/include/common.inc.php
index da23934ef..e40129c9f 100644
--- a/include/common.inc.php
+++ b/include/common.inc.php
@@ -109,6 +109,8 @@ include(PHPWG_ROOT_PATH . 'include/template.class.php');
 include(PHPWG_ROOT_PATH . 'include/cache.class.php');
 include(PHPWG_ROOT_PATH . 'include/Logger.class.php');
 
+$page['execution_uuid'] = generate_key(10);
+
 $persistent_cache = new PersistentFileCache();
 
 // Database connection