//.........这里部分代码省略.........
                        mtrace("... used " . (microtime(1) - $pre_time) . " seconds");
                    }
                    mtrace("done.");
                }
            }
        }
    }
    mtrace("Finished quiz reports");
    mtrace('Starting admin reports');
    // Admin reports do not have a database table that lists them. Instead a
    // report includes cron.php with function report_reportname_cron() if it wishes
    // to be cronned. It is up to cron.php to handle e.g. if it only needs to
    // actually do anything occasionally.
    $reports = get_plugin_list('report');
    foreach ($reports as $report => $reportdir) {
        $cronfile = $reportdir . '/cron.php';
        if (file_exists($cronfile)) {
            require_once $cronfile;
            $cronfunction = 'report_' . $report . '_cron';
            mtrace('Processing cron function for ' . $report . '...', '');
            $pre_dbqueries = null;
            $pre_dbqueries = $DB->perf_get_queries();
            $pre_time = microtime(true);
            $cronfunction();
            if (isset($pre_dbqueries)) {
                mtrace("... used " . ($DB->perf_get_queries() - $pre_dbqueries) . " dbqueries");
                mtrace("... used " . round(microtime(true) - $pre_time, 2) . " seconds");
            }
            mtrace('done.');
        }
    }
    mtrace('Finished admin reports');
    mtrace('Starting main gradebook job ...');
    grade_cron();
    mtrace('done.');
    mtrace('Starting processing the event queue...');
    events_cron();
    mtrace('done.');
    if ($CFG->enablecompletion) {
        // Completion cron
        mtrace('Starting the completion cron...');
        require_once $CFG->libdir . '/completion/cron.php';
        completion_cron();
        mtrace('done');
    }
    if ($CFG->enableportfolios) {
        // Portfolio cron
        mtrace('Starting the portfolio cron...');
        require_once $CFG->libdir . '/portfoliolib.php';
        portfolio_cron();
        mtrace('done');
    }
    /// Run all core cron jobs, but not every time since they aren't too important.
    /// These don't have a timer to reduce load, so we'll use a random number
    /// to randomly choose the percentage of times we should run these jobs.
    srand((double) microtime() * 10000000);
    $random100 = rand(0, 100);
    if ($random100 < 20) {
        // Approximately 20% of the time.
        mtrace("Running clean-up tasks...");
        /// Delete users who haven't confirmed within required period
        if (!empty($CFG->deleteunconfirmed)) {
            $cuttime = $timenow - $CFG->deleteunconfirmed * 3600;
            $rs = $DB->get_recordset_sql("SELECT id, firstname, lastname\n                                             FROM {user}\n                                            WHERE confirmed = 0 AND firstaccess > 0\n                                                  AND firstaccess < ?", array($cuttime));
            foreach ($rs as $user) {
                if ($DB->delete_records('user', array('id' => $user->id))) {

//.........这里部分代码省略.........
        }
    }
    get_mailer('close');
    mtrace("Finished activity modules");
    mtrace("Starting blocks");
    if ($blocks = $DB->get_records_select("block", "cron > 0 AND ((? - lastcron) > cron) AND visible = 1", array($timenow))) {
        // We will need the base class.
        require_once $CFG->dirroot . '/blocks/moodleblock.class.php';
        foreach ($blocks as $block) {
            $blockfile = $CFG->dirroot . '/blocks/' . $block->name . '/block_' . $block->name . '.php';
            if (file_exists($blockfile)) {
                require_once $blockfile;
                $classname = 'block_' . $block->name;
                $blockobj = new $classname();
                if (method_exists($blockobj, 'cron')) {
                    mtrace("Processing cron function for " . $block->name . '....', '');
                    cron_trace_time_and_memory();
                    if ($blockobj->cron()) {
                        $DB->set_field('block', 'lastcron', $timenow, array('id' => $block->id));
                    }
                    // Reset possible changes by blocks to time_limit. MDL-11597
                    @set_time_limit(0);
                    mtrace('done.');
                }
            }
        }
    }
    mtrace('Finished blocks');
    mtrace('Starting admin reports');
    cron_execute_plugin_type('report');
    mtrace('Finished admin reports');
    mtrace('Starting main gradebook job...');
    cron_trace_time_and_memory();
    grade_cron();
    mtrace('done.');
    mtrace('Starting processing the event queue...');
    cron_trace_time_and_memory();
    events_cron();
    mtrace('done.');
    if ($CFG->enablecompletion) {
        // Completion cron
        mtrace('Starting the completion cron...');
        cron_trace_time_and_memory();
        require_once $CFG->dirroot . '/completion/cron.php';
        completion_cron();
        mtrace('done');
    }
    if ($CFG->enableportfolios) {
        // Portfolio cron
        mtrace('Starting the portfolio cron...');
        cron_trace_time_and_memory();
        require_once $CFG->libdir . '/portfoliolib.php';
        portfolio_cron();
        mtrace('done');
    }
    //now do plagiarism checks
    require_once $CFG->libdir . '/plagiarismlib.php';
    plagiarism_cron();
    mtrace('Starting course reports');
    cron_execute_plugin_type('coursereport');
    mtrace('Finished course reports');
    // run gradebook import/export/report cron
    mtrace('Starting gradebook plugins');
    cron_execute_plugin_type('gradeimport');
    cron_execute_plugin_type('gradeexport');
    cron_execute_plugin_type('gradereport');

 /**
  * Do the job.
  * Throw exceptions on errors (the job will be retried).
  */
 public function execute()
 {
     global $CFG;
     require_once $CFG->libdir . '/gradelib.php';
     grade_cron();
 }