MDL-67211 Tasks: Add cron_enabled setting.

Co-authored-by: Sam Marshall <s.marshall@open.ac.uk>

admin/cli/adhoc_task.php

@@ -37,11 +37,13 @@ list($options, $unrecognized) = cli_get_params(
         'showsql' => false,
         'showdebugging' => false,
         'ignorelimits' => false,
+        'force' => false,
     ], [
         'h' => 'help',
         'e' => 'execute',
         'k' => 'keep-alive',
         'i' => 'ignorelimits',
+        'f' => 'force',
     ]
 );
 
@@ -61,6 +63,7 @@ Options:
  -e, --execute             Run all queued adhoc tasks
  -k, --keep-alive=N        Keep this script alive for N seconds and poll for new adhoc tasks
  -i  --ignorelimits        Ignore task_adhoc_concurrency_limit and task_adhoc_max_runtime limits
+ -f, --force               Run even if cron is disabled
 
 Example:
 \$sudo -u www-data /usr/bin/php admin/cli/adhoc_task.php --execute
@@ -92,6 +95,12 @@ if (moodle_needs_upgrading()) {
 if (empty($options['execute'])) {
     exit(0);
 }
+
+if (!get_config('core', 'cron_enabled') && !$options['force']) {
+    mtrace('Cron is disabled. Use --force to override.');
+    exit(1);
+}
+
 if (empty($options['keep-alive'])) {
     $options['keep-alive'] = 0;
 }

admin/cli/cron.php

@@ -36,14 +36,23 @@ require_once($CFG->libdir.'/cronlib.php');
 
 // now get cli options
 list($options, $unrecognized) = cli_get_params(
-    array(
+    [
         'help' => false,
         'stop' => false,
-    ),
-    array(
+        'list' => false,
+        'force' => false,
+        'enable' => false,
+        'disable' => false,
+        'disable-wait' => false,
+    ], [
         'h' => 'help',
         's' => 'stop',
-    )
+        'l' => 'list',
+        'f' => 'force',
+        'e' => 'enable',
+        'd' => 'disable',
+        'w' => 'disable-wait',
+    ]
 );
 
 if ($unrecognized) {
@@ -56,8 +65,13 @@ if ($options['help']) {
 "Execute periodic cron actions.
 
 Options:
--h, --help            Print out this help
--s, --stop            Notify all other running cron processes to stop after the current task
+-h, --help               Print out this help
+-s, --stop               Notify all other running cron processes to stop after the current task
+-l, --list               Show the list of currently running tasks and how long they have been running
+-f, --force              Execute task even if cron is disabled
+-e, --enable             Enable cron
+-d, --disable            Disable cron
+-w, --disable-wait=600   Disable cron and wait until all tasks finished or fail after N seconds (optional param)
 
 Example:
 \$sudo -u www-data /usr/bin/php admin/cli/cron.php
@@ -74,6 +88,91 @@ if ($options['stop']) {
     die;
 }
 
+if ($options['enable']) {
+    set_config('cron_enabled', 1);
+    mtrace('Cron has been enabled for the site.');
+    exit(0);
+}
+
+if ($options['disable']) {
+    set_config('cron_enabled', 0);
+    \core\task\manager::clear_static_caches();
+    mtrace('Cron has been disabled for the site.');
+    exit(0);
+}
+
+if ($options['list']) {
+    $tasks = \core\task\manager::get_running_tasks();
+    mtrace('The list of currently running tasks:');
+    $format = "%7s %-12s %-9s %-20s %-52s\n";
+    printf ($format,
+        'PID',
+        'HOST',
+        'TYPE',
+        'TIME',
+        'CLASSNAME'
+    );
+    foreach ($tasks as $task) {
+        printf ($format,
+            $task->pid,
+            substr($task->hostname, 0, 12),
+            $task->type,
+            format_time(time() - $task->timestarted),
+            substr($task->classname, 0, 52)
+        );
+    }
+    exit(0);
+}
+
+if ($wait = $options['disable-wait']) {
+    $started = time();
+    if (true === $wait) {
+        // Default waiting time.
+        $waitsec = 600;
+    } else {
+        $waitsec = $wait;
+        $wait = true;
+    }
+
+    set_config('cron_enabled', 0);
+    \core\task\manager::clear_static_caches();
+    mtrace('Cron has been disabled for the site.');
+    mtrace('Allocating '. format_time($waitsec) . ' for the tasks to finish.');
+
+    $lastcount = 0;
+    while ($wait) {
+        $tasks = \core\task\manager::get_running_tasks();
+
+        if (count($tasks) == 0) {
+            mtrace('');
+            mtrace('All scheduled and adhoc tasks finished.');
+            exit(0);
+        }
+
+        if (time() - $started >= $waitsec) {
+            mtrace('');
+            mtrace('Wait time ('. format_time($waitsec) . ') elapsed, but ' . count($tasks) . ' task(s) still running.');
+            mtrace('Exiting with code 1.');
+            exit(1);
+        }
+
+        if (count($tasks) !== $lastcount) {
+            mtrace('');
+            mtrace(count($tasks) . " tasks currently running.", '');
+            $lastcount = count($tasks);
+        } else {
+            mtrace('.', '');
+        }
+
+        sleep(1);
+    }
+}
+
+if (!get_config('core', 'cron_enabled') && !$options['force']) {
+    mtrace('Cron is disabled. Use --force to override.');
+    exit(1);
+}
+
 \core\local\cli\shutdown::script_supports_graceful_exit();
 
 cron_run();

admin/cli/scheduled_task.php

@@ -30,8 +30,17 @@ require_once("$CFG->libdir/clilib.php");
 require_once("$CFG->libdir/cronlib.php");
 
 list($options, $unrecognized) = cli_get_params(
-    array('help' => false, 'list' => false, 'execute' => false, 'showsql' => false, 'showdebugging' => false),
-    array('h' => 'help')
+    [
+        'help' => false,
+        'list' => false,
+        'execute' => false,
+        'showsql' => false,
+        'showdebugging' => false,
+        'force' => false,
+    ], [
+        'h' => 'help',
+        'f' => 'force',
+    ]
 );
 
 if ($unrecognized) {
@@ -49,6 +58,7 @@ if ($options['help'] or (!$options['list'] and !$options['execute'])) {
     --showsql             Show sql queries before they are executed
     --showdebugging       Show developer level debugging information
     -h, --help            Print out this help
+    -f, --force           Execute task even if cron is disabled
 
     Example:
     \$sudo -u www-data /usr/bin/php admin/cli/scheduled_task.php --execute=\\core\\task\\session_cleanup_task
@@ -121,6 +131,11 @@ if ($execute = $options['execute']) {
         exit(1);
     }
 
+    if (!get_config('core', 'cron_enabled') && !$options['force']) {
+        mtrace('Cron is disabled. Use --force to override.');
+        exit(1);
+    }
+
     \core\task\manager::scheduled_task_starting($task);
 
     // Increase memory limit.

admin/settings/server.php

@@ -216,6 +216,16 @@ $ADMIN->add('server', $temp);
 
 $ADMIN->add('server', new admin_category('taskconfig', new lang_string('taskadmintitle', 'admin')));
 $temp = new admin_settingpage('taskprocessing', new lang_string('taskprocessing','admin'));
+
+$setting = new admin_setting_configcheckbox(
+    'cron_enabled',
+    new lang_string('cron_enabled', 'admin'),
+    new lang_string('cron_enabled_desc', 'admin'),
+    1
+);
+$setting->set_updatedcallback('theme_reset_static_caches');
+$temp->add($setting);
+
 $temp->add(
     new admin_setting_configtext(
         'task_scheduled_concurrency_limit',

admin/tool/task/lang/en/tool_task.php

@@ -39,6 +39,7 @@ $string['classname'] = 'Class name';
 $string['clearfaildelay_confirm'] = 'Are you sure you want to clear the fail delay for task \'{$a}\'? After clearing the delay, the task will run according to its normal schedule.';
 $string['component'] = 'Component';
 $string['corecomponent'] = 'Core';
+$string['crondisabled'] = 'Cron is disabled. No new tasks will be started. The system will not operate properly until it is enabled again.';
 $string['cronok'] = 'Cron is running frequently';
 $string['default'] = 'Default';
 $string['defaultx'] = 'Default: {$a}';

admin/tool/task/renderer.php

@@ -261,6 +261,16 @@ class tool_task_renderer extends plugin_renderer_base {
         return $cell;
     }
 
+    /**
+     * Displays a warning on the page if cron is disabled.
+     *
+     * @return string HTML code for information about cron being disabled
+     * @throws moodle_exception
+     */
+    public function cron_disabled(): string {
+        return $this->output->notification(get_string('crondisabled', 'tool_task'), 'warning');
+    }
+
     /**
      * Renders a link back to the scheduled tasks page (used from the 'run now' screen).
      *

admin/tool/task/runningtasks.php

@@ -39,6 +39,11 @@ admin_externalpage_setup('runningtasks');
 
 echo $OUTPUT->header();
 
+if (!get_config('core', 'cron_enabled')) {
+    $renderer = $PAGE->get_renderer('tool_task');
+    echo $renderer->cron_disabled();
+}
+
 $table = new \tool_task\running_tasks_table();
 $table->baseurl = $pageurl;
 $table->out(100, false);

admin/tool/task/scheduledtasks.php

@@ -95,6 +95,9 @@ if ($mform && ($mform->is_cancelled() || !empty($CFG->preventscheduledtaskchange
 
 } else {
     echo $OUTPUT->header();
+    if (!get_config('core', 'cron_enabled')) {
+        echo $renderer->cron_disabled();
+    }
     $tasks = core\task\manager::get_all_scheduled_tasks();
     echo $renderer->scheduled_tasks_table($tasks, $lastchanged);
     echo $OUTPUT->footer();

admin/tool/task/tests/behat/cron_disabled.feature

@@ -0,0 +1,20 @@
+@tool @tool_task
+Feature: See warning message if cron is disabled
+  In order to manage scheduled tasks
+  As a Moodle Administrator
+  I need to be able to view a warning message if cron is disabled
+
+  Background:
+    Given I log in as "admin"
+
+  Scenario: If cron is disabled, I should see the message
+    When the following config values are set as admin:
+      | cron_enabled | 0 |
+    And I navigate to "Server > Tasks > Scheduled tasks" in site administration
+    Then I should see "Cron is disabled"
+
+  Scenario: If cron is enabled, I should not see the message
+    When the following config values are set as admin:
+      | cron_enabled | 1 |
+    And I navigate to "Server > Tasks > Scheduled tasks" in site administration
+    Then I should not see "Cron is disabled"

lang/en/admin.php

@@ -424,6 +424,8 @@ $string['courseswithsummarieslimit'] = 'Courses with summaries limit';
 $string['creatornewroleid'] = 'Creators\' role in new courses';
 $string['creatornewroleid_help'] = 'If the user does not already have the permission to manage the new course, the user is automatically enrolled using this role.';
 $string['cron'] = 'Cron';
+$string['cron_enabled'] = 'Enable cron';
+$string['cron_enabled_desc'] = 'If disabled prevents the system from starting new background tasks. This option is intended for temporary use only, e.g. before a restart. Leaving it off for a long time will prevent important functionality from working.';
 $string['cron_help'] = 'The cron.php script runs a number of tasks at different scheduled intervals, such as sending forum post notification emails. The script should be run regularly - ideally every minute.';
 $string['cron_link'] = 'admin/cron';
 $string['cronclionly'] = 'Cron execution via command line only';

lib/classes/task/manager.php

@@ -1095,7 +1095,7 @@ class manager {
 
             // Shell-escaped task name.
             $classname = get_class($task);
-            $taskarg   = escapeshellarg("--execute={$classname}");
+            $taskarg   = escapeshellarg("--execute={$classname}") . " " . escapeshellarg("--force");
 
             // Build the CLI command.
             $command = "{$phpbinary} {$scriptpath} {$taskarg}";

lib/outputlib.php

@@ -270,6 +270,16 @@ function theme_reset_all_caches() {
     }
 }
 
+/**
+ * Reset static caches.
+ *
+ * This method indicates that all running cron processes should exit at the
+ * next opportunity.
+ */
+function theme_reset_static_caches() {
+    \core\task\manager::clear_static_caches();
+}
+
 /**
  * Enable or disable theme designer mode.
  *