X-Git-Url: https://vcs.fsf.org/?a=blobdiff_plain;f=CRM%2FCore%2FLock.php;h=1a92a7665dc2a25b9211e9ffa0d4648a125b5646;hb=f8a02ee16658006de93685cc33ded184d50903b8;hp=b594e0b0efcb2a4acce3043dee00dc6f2ee69035;hpb=f8652a9eb1111439ac77b5535a8622db691b1a1b;p=civicrm-core.git

diff --git a/CRM/Core/Lock.php b/CRM/Core/Lock.php
index b594e0b0ef..1a92a7665d 100644
--- a/CRM/Core/Lock.php
+++ b/CRM/Core/Lock.php
@@ -3,7 +3,7 @@
  +--------------------------------------------------------------------+
  | CiviCRM version 4.7                                                |
  +--------------------------------------------------------------------+
- | Copyright CiviCRM LLC (c) 2004-2015                                |
+ | Copyright CiviCRM LLC (c) 2004-2017                                |
  +--------------------------------------------------------------------+
  | This file is a part of CiviCRM.                                    |
  |                                                                    |
@@ -28,12 +28,22 @@
 /**
  *
  * @package CRM
- * @copyright CiviCRM LLC (c) 2004-2015
+ * @copyright CiviCRM LLC (c) 2004-2017
  * $Id$
  *
  */
 class CRM_Core_Lock implements \Civi\Core\Lock\LockInterface {
 
+  /**
+   * This variable (despite it's name) roughly translates to 'lock that we actually care about'.
+   *
+   * Prior to version 5.7.5 mysql only supports a single named lock. This variable is
+   * part of the skullduggery involved in 'say it's no so Frank'.
+   *
+   * See further comments on the aquire function.
+   *
+   * @var bool
+   */
   static $jobLog = FALSE;
 
   // lets have a 3 second timeout for now
@@ -43,6 +53,8 @@ class CRM_Core_Lock implements \Civi\Core\Lock\LockInterface {
 
   protected $_name;
 
+  protected $_id;
+
   /**
    * Use MySQL's GET_LOCK(). Locks are shared across all Civi instances
    * on the same MySQL server.
@@ -121,8 +133,10 @@ class CRM_Core_Lock implements \Civi\Core\Lock\LockInterface {
     else {
       $this->_name = $database . '.' . $domainID . '.' . $name;
     }
+    // MySQL 5.7 doesn't like long lock names so creating a lock id
+    $this->_id = sha1($this->_name);
     if (defined('CIVICRM_LOCK_DEBUG')) {
-      CRM_Core_Error::debug_log_message('trying to construct lock for ' . $this->_name);
+      CRM_Core_Error::debug_log_message('trying to construct lock for ' . $this->_name . '(' . $this->_id . ')');
     }
     $this->_timeout = $timeout !== NULL ? $timeout : self::TIMEOUT;
   }
@@ -134,6 +148,28 @@ class CRM_Core_Lock implements \Civi\Core\Lock\LockInterface {
   /**
    * Acquire lock.
    *
+   * The advantage of mysql locks is that they can be used across processes. However, only one
+   * can be used at once within a process. An attempt to use a second one within a process
+   * prior to mysql 5.7.5 results in the first being released.
+   *
+   * The process here is
+   *  1) first attempt to grab a lock for a mailing job - self::jobLog will be populated with the
+   * lock id & a mysql lock will be created for the ID.
+   *
+   * If a second function in the same process attempts to grab the lock it will enter the hackyHandleBrokenCode routine
+   * which says 'I won't break a mailing lock for you but if you are not a civimail send process I'll let you
+   * pretend you have a lock already and you can go ahead with whatever you were doing under the delusion you
+   * have a lock.
+   *
+   * @todo bypass hackyHandleBrokenCode for mysql version 5.7.5+
+   *
+   * If a second function in a separate process attempts to grab the lock already in use it should be rejected,
+   * but it appears it IS allowed to grab a different lock & unlike in the same process the first lock won't be released.
+   *
+   * All this means CiviMail locks are first class citizens & any other process gets a 'best effort lock'.
+   *
+   * @todo document naming convention for CiviMail locks as this is key to ensuring they work properly.
+   *
    * @param int $timeout
    *
    * @return bool
@@ -147,22 +183,22 @@ class CRM_Core_Lock implements \Civi\Core\Lock\LockInterface {
 
       $query = "SELECT GET_LOCK( %1, %2 )";
       $params = array(
-        1 => array($this->_name, 'String'),
+        1 => array($this->_id, 'String'),
         2 => array($timeout ? $timeout : $this->_timeout, 'Integer'),
       );
       $res = CRM_Core_DAO::singleValueQuery($query, $params);
       if ($res) {
         if (defined('CIVICRM_LOCK_DEBUG')) {
-          CRM_Core_Error::debug_log_message('acquire lock for ' . $this->_name);
+          CRM_Core_Error::debug_log_message('acquire lock for ' . $this->_name . '(' . $this->_id . ')');
         }
         $this->_hasLock = TRUE;
         if (stristr($this->_name, 'data.mailing.job.')) {
-          self::$jobLog = $this->_name;
+          self::$jobLog = $this->_id;
         }
       }
       else {
         if (defined('CIVICRM_LOCK_DEBUG')) {
-          CRM_Core_Error::debug_log_message('failed to acquire lock for ' . $this->_name);
+          CRM_Core_Error::debug_log_message('failed to acquire lock for ' . $this->_name . '(' . $this->_id . ')');
         }
       }
     }
@@ -175,16 +211,16 @@ class CRM_Core_Lock implements \Civi\Core\Lock\LockInterface {
   public function release() {
     if ($this->_hasLock) {
       if (defined('CIVICRM_LOCK_DEBUG')) {
-        CRM_Core_Error::debug_log_message('release lock for ' . $this->_name);
+        CRM_Core_Error::debug_log_message('release lock for ' . $this->_name . '(' . $this->_id . ')');
       }
       $this->_hasLock = FALSE;
 
-      if (self::$jobLog == $this->_name) {
+      if (self::$jobLog == $this->_id) {
         self::$jobLog = FALSE;
       }
 
       $query = "SELECT RELEASE_LOCK( %1 )";
-      $params = array(1 => array($this->_name, 'String'));
+      $params = array(1 => array($this->_id, 'String'));
       return CRM_Core_DAO::singleValueQuery($query, $params);
     }
   }
@@ -194,7 +230,7 @@ class CRM_Core_Lock implements \Civi\Core\Lock\LockInterface {
    */
   public function isFree() {
     $query = "SELECT IS_FREE_LOCK( %1 )";
-    $params = array(1 => array($this->_name, 'String'));
+    $params = array(1 => array($this->_id, 'String'));
     return CRM_Core_DAO::singleValueQuery($query, $params);
   }
 
@@ -220,11 +256,11 @@ class CRM_Core_Lock implements \Civi\Core\Lock\LockInterface {
    */
   public function hackyHandleBrokenCode($jobLog) {
     if (stristr($this->_name, 'job')) {
-      CRM_Core_Error::debug_log_message('lock acquisition for ' . $this->_name . ' attempted when ' . $jobLog . ' is not released');
-      throw new CRM_Core_Exception('lock acquisition for ' . $this->_name . ' attempted when ' . $jobLog . ' is not released');
+      CRM_Core_Error::debug_log_message('lock acquisition for ' . $this->_name . '(' . $this->_id . ')' . ' attempted when ' . $jobLog . ' is not released');
+      throw new CRM_Core_Exception('lock acquisition for ' . $this->_name . '(' . $this->_id . ')' . ' attempted when ' . $jobLog . ' is not released');
     }
     if (defined('CIVICRM_LOCK_DEBUG')) {
-      CRM_Core_Error::debug_log_message('(CRM-12856) faking lock for ' . $this->_name);
+      CRM_Core_Error::debug_log_message('(CRM-12856) faking lock for ' . $this->_name . '(' . $this->_id . ')');
     }
     $this->_hasLock = TRUE;
     return TRUE;