Merge "grunt: Add Karma task for automated QUnit testing in browsers"

[lhc/web/wiklou.git] / includes / poolcounter / PoolCounter.php

diff --git a/includes/poolcounter/PoolCounter.php b/includes/poolcounter/PoolCounter.php
index 34953c0..5692d73 100644 (file)
--- a/includes/poolcounter/PoolCounter.php
+++ b/includes/poolcounter/PoolCounter.php
@@ -34,7 +34,10 @@
  * minutes and hundreds of read hits.
  *
  * The PoolCounter provides semaphore semantics for restricting the number
- * of workers that may be concurrently performing such single task.
+ * of workers that may be concurrently performing such single task. Only one
+ * key can be locked by any PoolCounter instance of a process, except for keys
+ * that start with "nowait:". However, only 0 timeouts (non-blocking requests)
+ * can be used with "nowait:" keys.
  *
  * By default PoolCounter_Stub is used, which provides no locking. You
  * can get a useful one in the PoolCounter extension.
@@ -53,23 +56,47 @@ abstract class PoolCounter {
 
        /** @var string All workers with the same key share the lock */
        protected $key;
-       /** @var int Maximum number of workers doing the task simultaneously */
+       /** @var int Maximum number of workers working on tasks with the same key simultaneously */
        protected $workers;
+       /**
+        * Maximum number of workers working on this task type, regardless of key.
+        * 0 means unlimited. Max allowed value is 65536.
+        * The way the slot limit is enforced is overzealous - this option should be used with caution.
+        * @var int
+        */
+       protected $slots = 0;
        /** @var int If this number of workers are already working/waiting, fail instead of wait */
        protected $maxqueue;
        /** @var float Maximum time in seconds to wait for the lock */
        protected $timeout;
 
+       /**
+        * @var boolean Whether the key is a "might wait" key
+        */
+       private $isMightWaitKey;
+       /**
+        * @var boolean Whether this process holds a "might wait" lock key
+        */
+       private static $acquiredMightWaitKey = 0;
+
        /**
         * @param array $conf
         * @param string $type
         * @param string $key
         */
        protected function __construct( $conf, $type, $key ) {
-               $this->key = $key;
                $this->workers = $conf['workers'];
                $this->maxqueue = $conf['maxqueue'];
                $this->timeout = $conf['timeout'];
+               if ( isset( $conf['slots'] ) ) {
+                       $this->slots = $conf['slots'];
+               }
+
+               if ( $this->slots ) {
+                       $key = $this->hashKeyIntoSlots( $key, $this->slots );
+               }
+               $this->key = $key;
+               $this->isMightWaitKey = !preg_match( '/^nowait:/', $this->key );
        }
 
        /**
@@ -118,9 +145,65 @@ abstract class PoolCounter {
         * Lets another one grab the lock, and returns the workers
         * waiting on acquireForAnyone()
         *
-        * @return Status value is one of Released/NotLocked/Error
+        * @return Status Value is one of Released/NotLocked/Error
         */
        abstract public function release();
+
+       /**
+        * Checks that the lock request is sane.
+        * @return Status - good for sane requests fatal for insane
+        * @since 1.25
+        */
+       final protected function precheckAcquire() {
+               if ( $this->isMightWaitKey ) {
+                       if ( self::$acquiredMightWaitKey ) {
+                               /*
+                                * The poolcounter itself is quite happy to allow you to wait
+                                * on another lock while you have a lock you waited on already
+                                * but we think that it is unlikely to be a good idea.  So we
+                                * made it an error.  If you are _really_ _really_ sure it is a
+                                * good idea then feel free to implement an unsafe flag or
+                                * something.
+                                */
+                               return Status::newFatal( 'poolcounter-usage-error',
+                                       'You may only aquire a single non-nowait lock.' );
+                       }
+               } elseif ( $this->timeout !== 0 ) {
+                       return Status::newFatal( 'poolcounter-usage-error',
+                               'Locks starting in nowait: must have 0 timeout.' );
+               }
+               return Status::newGood();
+       }
+
+       /**
+        * Update any lock tracking information when the lock is acquired
+        * @since 1.25
+        */
+       final protected function onAcquire() {
+               self::$acquiredMightWaitKey |= $this->isMightWaitKey;
+       }
+
+       /**
+        * Update any lock tracking information when the lock is released
+        * @since 1.25
+        */
+       final protected function onRelease() {
+               self::$acquiredMightWaitKey &= !$this->isMightWaitKey;
+       }
+
+       /**
+        * Given a key (any string) and the number of lots, returns a slot number (an integer from the [0..($slots-1)] range).
+        * This is used for a global limit on the number of instances  of a given type that can acquire a lock.
+        * The hashing is deterministic so that PoolCounter::$workers is always an upper limit of how many instances with
+        * the same key can acquire a lock.
+        *
+        * @param string $key PoolCounter instance key (any string)
+        * @param int $slots The number of slots (max allowed value is 65536)
+        * @return int
+        */
+       protected function hashKeyIntoSlots( $key, $slots ) {
+               return hexdec( substr( sha1( $key ), 0, 4 ) ) % $slots;
+       }
 }
 
 // @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps