diff core/lib/Drupal/Core/Lock/LockBackendAbstract.php @ 0:4c8ae668cc8c

Initial import (non-working)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/lib/Drupal/Core/Lock/LockBackendAbstract.php	Wed Nov 29 16:09:58 2017 +0000
@@ -0,0 +1,75 @@
+<?php
+
+namespace Drupal\Core\Lock;
+
+/**
+ * Non backend related common methods implementation for lock backends.
+ *
+ * @ingroup lock
+ */
+abstract class LockBackendAbstract implements LockBackendInterface {
+
+  /**
+   * Current page lock token identifier.
+   *
+   * @var string
+   */
+  protected $lockId;
+
+  /**
+   * Existing locks for this page.
+   *
+   * @var array
+   */
+  protected $locks = [];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function wait($name, $delay = 30) {
+    // Pause the process for short periods between calling
+    // lock_may_be_available(). This prevents hitting the database with constant
+    // database queries while waiting, which could lead to performance issues.
+    // However, if the wait period is too long, there is the potential for a
+    // large number of processes to be blocked waiting for a lock, especially
+    // if the item being rebuilt is commonly requested. To address both of these
+    // concerns, begin waiting for 25ms, then add 25ms to the wait period each
+    // time until it reaches 500ms. After this point polling will continue every
+    // 500ms until $delay is reached.
+
+    // $delay is passed in seconds, but we will be using usleep(), which takes
+    // microseconds as a parameter. Multiply it by 1 million so that all
+    // further numbers are equivalent.
+    $delay = (int) $delay * 1000000;
+
+    // Begin sleeping at 25ms.
+    $sleep = 25000;
+    while ($delay > 0) {
+      // This function should only be called by a request that failed to get a
+      // lock, so we sleep first to give the parallel request a chance to finish
+      // and release the lock.
+      usleep($sleep);
+      // After each sleep, increase the value of $sleep until it reaches
+      // 500ms, to reduce the potential for a lock stampede.
+      $delay = $delay - $sleep;
+      $sleep = min(500000, $sleep + 25000, $delay);
+      if ($this->lockMayBeAvailable($name)) {
+        // No longer need to wait.
+        return FALSE;
+      }
+    }
+    // The caller must still wait longer to get the lock.
+    return TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getLockId() {
+    if (!isset($this->lockId)) {
+      $this->lockId = uniqid(mt_rand(), TRUE);
+    }
+    return $this->lockId;
+  }
+
+}