From 96e1633f57b2076e33c766759129694ec28f869f Mon Sep 17 00:00:00 2001
From: Marina Glancy <marina@moodle.com>
Date: Wed, 9 Aug 2017 08:04:00 +0800
Subject: [PATCH] MDL-59768 tasks: schedule task only if it is not scheduled

---
 backup/moodle2/restore_stepslib.php |  2 +-
 lib/classes/task/manager.php        | 26 ++++++++++++++++++++-
 lib/tests/adhoc_task_test.php       | 36 +++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/backup/moodle2/restore_stepslib.php b/backup/moodle2/restore_stepslib.php
index dfcf545e91c..10872f824f1 100644
--- a/backup/moodle2/restore_stepslib.php
+++ b/backup/moodle2/restore_stepslib.php
@@ -5560,6 +5560,6 @@ class restore_calendar_action_events extends restore_execution_step {
         // The task will automatically populate all data.
         $task = new \core\task\refresh_mod_calendar_events_task();
         $task->set_custom_data(array('courseid' => $this->get_courseid()));
-        \core\task\manager::queue_adhoc_task($task);
+        \core\task\manager::queue_adhoc_task($task, true);
     }
 }
diff --git a/lib/classes/task/manager.php b/lib/classes/task/manager.php
index 106878b8bcf..b19b689890d 100644
--- a/lib/classes/task/manager.php
+++ b/lib/classes/task/manager.php
@@ -125,13 +125,30 @@ class manager {
         $DB->delete_records_select('task_scheduled', $sql, $params);
     }
 
+    /**
+     * Checks if the task with the same classname, component and customdata is already scheduled
+     *
+     * @param adhoc_task $task
+     * @return bool
+     */
+    protected static function task_is_scheduled($task) {
+        global $DB;
+        $record = self::record_from_adhoc_task($task);
+        $params = [$record->classname, $record->component, $record->customdata];
+        $sql = 'classname = ? AND component = ? AND ' .
+            $DB->sql_compare_text('customdata', \core_text::strlen($record->customdata) + 1) . ' = ?';
+        return $DB->record_exists_select('task_adhoc', $sql, $params);
+    }
+
     /**
      * Queue an adhoc task to run in the background.
      *
      * @param \core\task\adhoc_task $task - The new adhoc task information to store.
+     * @param bool $checkforexisting - If set to true and the task with the same classname, component and customdata
+     *     is already scheduled then it will not schedule a new task. Can be used only for ASAP tasks.
      * @return boolean - True if the config was saved.
      */
-    public static function queue_adhoc_task(adhoc_task $task) {
+    public static function queue_adhoc_task(adhoc_task $task, $checkforexisting = false) {
         global $DB;
 
         $record = self::record_from_adhoc_task($task);
@@ -139,6 +156,13 @@ class manager {
         if (!$task->get_next_run_time()) {
             $record->nextruntime = time() - 1;
         }
+
+        // Check if the same task is already scheduled.
+        if ($checkforexisting && self::task_is_scheduled($task)) {
+            return false;
+        }
+
+        // Queue the task.
         $result = $DB->insert_record('task_adhoc', $record);
 
         return $result;
diff --git a/lib/tests/adhoc_task_test.php b/lib/tests/adhoc_task_test.php
index d1ec1d88390..e4ebcacc71e 100644
--- a/lib/tests/adhoc_task_test.php
+++ b/lib/tests/adhoc_task_test.php
@@ -149,4 +149,40 @@ class core_adhoc_task_testcase extends advanced_testcase {
             $this->assertInstanceOf('\\core\\task\\adhoc_test2_task', $task);
         }
     }
+
+    /**
+     * Test queue_adhoc_task "if not scheduled".
+     */
+    public function test_queue_adhoc_task_if_not_scheduled() {
+        $this->resetAfterTest(true);
+
+        // Schedule adhoc task.
+        $task1 = new \core\task\adhoc_test_task();
+        $task1->set_custom_data(array('courseid' => 10));
+        $this->assertNotEmpty(\core\task\manager::queue_adhoc_task($task1, true));
+        $this->assertEquals(1, count(\core\task\manager::get_adhoc_tasks('core\task\adhoc_test_task')));
+
+        // Schedule same adhoc task with different custom data.
+        $task2 = new \core\task\adhoc_test_task();
+        $task2->set_custom_data(array('courseid' => 1));
+        $this->assertNotEmpty(\core\task\manager::queue_adhoc_task($task2, true));
+        $this->assertEquals(2, count(\core\task\manager::get_adhoc_tasks('core\task\adhoc_test_task')));
+
+        // Schedule same adhoc task with same custom data.
+        $task3 = new \core\task\adhoc_test_task();
+        $task3->set_custom_data(array('courseid' => 1));
+        $this->assertEmpty(\core\task\manager::queue_adhoc_task($task3, true));
+        $this->assertEquals(2, count(\core\task\manager::get_adhoc_tasks('core\task\adhoc_test_task')));
+
+        // Schedule same adhoc task without custom data.
+        $task4 = new \core\task\adhoc_test_task();
+        $this->assertNotEmpty(\core\task\manager::queue_adhoc_task($task4, true));
+        $this->assertEquals(3, count(\core\task\manager::get_adhoc_tasks('core\task\adhoc_test_task')));
+
+        // Schedule same adhoc task without custom data (again).
+        $task5 = new \core\task\adhoc_test_task();
+        $this->assertEmpty(\core\task\manager::queue_adhoc_task($task5, true));
+        $this->assertEquals(3, count(\core\task\manager::get_adhoc_tasks('core\task\adhoc_test_task')));
+
+    }
 }