- Patch #44947 by rkerr / Moshe: fixed race condition in session handling, reduced query overhead of session handling, reduced database overhead of session handling.

1 files changed, 38 insertions, 27 deletions

diff --git a/includes/session.inc b/includes/session.inc
index a838bdc94..48938d2ca 100644
--- a/includes/session.inc
+++ b/includes/session.inc
@@ -6,40 +6,43 @@
  * User session handling functions.
  */
 
-/*** Session functions *****************************************************/
-
 function sess_open($save_path, $session_name) {
-  return 1;
+  return TRUE;
 }
 
 function sess_close() {
-  return 1;
+  return TRUE;
 }
 
 function sess_read($key) {
   global $user;
 
-  $result = db_query("SELECT u.*, s.* FROM {users} u INNER JOIN {sessions} s ON u.uid = s.uid WHERE s.sid = '%s'", $key);
-
+  // retrieve data for a $user object
+  $result = db_query("SELECT sid FROM {sessions} WHERE sid = '%s'", $key);
   if (!db_num_rows($result)) {
-    db_query("INSERT INTO {sessions} (sid, uid, hostname, timestamp) VALUES ('%s', 0, '%s', %d)", $key, $_SERVER["REMOTE_ADDR"], time());
     $result = db_query("SELECT u.* FROM {users} u WHERE u.uid = 0");
   }
+  else {
+    $result = db_query("SELECT u.*, s.* FROM {users} u INNER JOIN {sessions} s ON u.uid = s.uid WHERE s.sid = '%s'", $key);
+  }
 
+  // Build $user object:
   $user = db_fetch_object($result);
   $user = drupal_unpack($user);
-  $user->roles = array();
 
+  // Add roles element to $user:
+  $user->roles = array();
   if ($user->uid) {
     $user->roles[DRUPAL_AUTHENTICATED_RID] = 'authenticated user';
+
+    $result = db_query("SELECT r.rid, r.name FROM {role} r INNER JOIN {users_roles} ur ON ur.rid = r.rid WHERE ur.uid = %d", $user->uid);
+    while ($role = db_fetch_object($result)) {
+      $user->roles[$role->rid] = $role->name;
+    }
   }
   else {
     $user->roles[DRUPAL_ANONYMOUS_RID] = 'anonymous user';
   }
-  $result = db_query("SELECT r.rid, r.name FROM {role} r INNER JOIN {users_roles} ur ON ur.rid = r.rid WHERE ur.uid = %d", $user->uid);
-  while ($role = db_fetch_object($result)) {
-    $user->roles[$role->rid] = $role->name;
-  }
 
   return !empty($user->session) ? $user->session : '';
 }
@@ -47,11 +50,24 @@ function sess_read($key) {
 function sess_write($key, $value) {
   global $user;
 
-  db_query("UPDATE {sessions} SET uid = %d, cache = %d, hostname = '%s', session = '%s', timestamp = %d WHERE sid = '%s'", $user->uid, $user->cache, $_SERVER["REMOTE_ADDR"], $value, time(), $key);
-  if ($user->uid) {
-    db_query("UPDATE {users} SET access = %d WHERE uid = %d", time(), $user->uid);
+  $result = db_query("SELECT sid FROM {sessions} WHERE sid = '%s'", $key);
+
+  if (!db_num_rows($result)) {
+    // Only save session data when there is session data available.
+    if ($user->uid || $value) {
+      db_query("INSERT INTO {sessions} (sid, uid, cache, hostname, session, timestamp) VALUES ('%s', %d, %d, '%s', '%s', %d)", $key, $user->uid, $user->cache, $_SERVER["REMOTE_ADDR"], $value, time());
+    }
+  }
+  else {
+    db_query("UPDATE {sessions} SET uid = %d, cache = %d, hostname = '%s', session = '%s', timestamp = %d WHERE sid = '%s'", $user->uid, $user->cache, $_SERVER["REMOTE_ADDR"], $value, time(), $key);
+
+    // TODO: this can be an expensive query. Perhaps only execute it every x minutes. Requires investigation into cache expiration.
+    if ($user->uid) {
+      db_query("UPDATE {users} SET access = %d WHERE uid = %d", time(), $user->uid);
+    }
   }
-  return '';
+
+  return TRUE;
 }
 
 function sess_destroy($key) {
@@ -59,18 +75,13 @@ function sess_destroy($key) {
 }
 
 function sess_gc($lifetime) {
-
-  /*
-  **  Be sure to adjust 'php_value session.gc_maxlifetime' to a large enough
-  **   value.  For example, if you want user sessions to stay in your database
-  **   for three weeks before deleting them, you need to set gc_maxlifetime
-  **   to '1814400'.  At that value, only after a user doesn't log in after
-  **   three weeks (1814400 seconds) will his/her session be removed.
-  */
+  // Be sure to adjust 'php_value session.gc_maxlifetime' to a large enough
+  // value.  For example, if you want user sessions to stay in your database
+  // for three weeks before deleting them, you need to set gc_maxlifetime
+  // to '1814400'.  At that value, only after a user doesn't log in after
+  // three weeks (1814400 seconds) will his/her session be removed.
   db_query("DELETE FROM {sessions} WHERE timestamp < %d", time() - $lifetime);
 
-  return 1;
-
+  return TRUE;
 }
 
-