Encapsulate locks mechanics in "ProcessLock" class

src/mibew/libs/classes/Mibew/ProcessLock.php

@@ -0,0 +1,95 @@
+<?php
+/*
+ * This file is a part of Mibew Messenger.
+ *
+ * Copyright 2005-2014 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+namespace Mibew;
+
+use Mibew\Settings;
+
+/**
+ * Watch the process is ran only once.
+ */
+class ProcessLock
+{
+    /**
+     * Name of the lock.
+     *
+     * @var string
+     */
+    private $name;
+
+    /**
+     * Time to live of the lock.
+     *
+     * @var int
+     */
+    private $ttl;
+
+    /**
+     * Class constructor.
+     *
+     * @param string $name Name of the lock.
+     * @param int $ttl Time after the lock will be automatically released.
+     */
+    public function __construct($name, $ttl = 300)
+    {
+        $this->name = $name;
+        $this->ttl = $ttl;
+    }
+
+    /**
+     * Tries to get the lock.
+     *
+     * @return boolean True if the lock has been got and false otherwise.
+     */
+    public function get()
+    {
+        // Check if we can get the lock
+        $lock_timestamp = (int)Settings::get($this->getInternalName(), 0);
+        $is_lock_free = !$lock_timestamp
+            // Lock cannot be got for more than ttl.
+            || (time() - $lock_timestamp) > $this->ttl;
+
+        if (!$is_lock_free) {
+            return false;
+        }
+
+        // Get the lock
+        Settings::set($this->getInternalName(), time());
+
+        return true;
+    }
+
+    /**
+     * Releases the lock
+     */
+    public function release()
+    {
+        Settings::set($this->getInternalName(), '0');
+    }
+
+    /**
+     * Builds internal name of the lock.
+     *
+     * @return string
+     */
+    protected function getInternalName()
+    {
+        return '_' . $this->name . '_lock_time';
+    }
+}

src/mibew/libs/classes/Mibew/Thread.php

@@ -382,18 +382,10 @@ class Thread
             return;
         }
 
-        // We need to run only one instance of cleaning process. Use a lock with
+        // We need to run only one instance of cleaning process.
-        // last run timestamp.
+        $lock = new ProcessLock('threads_close_old');
-        $lock_timestamp = (int)Settings::get('_threads_close_old_lock_time', 0);
-        $is_lock_free = !$lock_timestamp
-            // Lock cannot be got for more than 5 minutes. If such situation
-            // take place we have a deadlock.
-            || (time() - $lock_timestamp) > 5 * 60;
-
-        if ($is_lock_free) {
-            // Get the lock
-            Settings::set('_threads_close_old_lock_time', time());
 
+        if ($lock->get()) {
             $query = "SELECT * FROM {thread} "
                 . "WHERE istate <> :state_closed "
                     . "AND istate <> :state_left "
@@ -454,7 +446,7 @@ class Thread
             }
 
             // Release the lock
-            Settings::set('_threads_close_old_lock_time', '0');
+            $lock->release();
         }
     }