Dynamique Cron Expression System Configuration

gistfile1.txt

+ Dans config.xml :
<config>
    <crontab>
        <jobs>
            <cron_task_identifier>
                <run>
                    <model>mon_module/cron::run</model>
                </run>
            </cron_task_identifier>
        </jobs>
    </crontab>
</config>

+ Dans system.xml :

    <sections>
        <my_section translate="label" module="mon_module">
            <label>Ma Section</label>
            <tab>mon_tab</tab>
            <sort_order>10</sort_order>
            <show_in_default>1</show_in_default>
            <show_in_website>0</show_in_website>
            <show_in_store>0</show_in_store>
            <groups>
                <cron translate="label" module="mon_module">
                    <label>Cron Configuration</label>
                    <sort_order>10</sort_order>
                    <show_in_default>1</show_in_default>
                    <show_in_website>0</show_in_website>
                    <show_in_store>0</show_in_store>
                    <fields>
                        <enabled translate="label">
                            <label>Enable Cron</label>
                            <frontend_type>select</frontend_type>
                            <source_model>adminhtml/system_config_source_yesno</source_model>
                            <sort_order>2</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>0</show_in_website>
                            <show_in_store>0</show_in_store>
                        </enabled>
                        <time translate="label">
                            <label>Start Time</label>
                            <frontend_type>time</frontend_type>
                            <sort_order>3</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>0</show_in_website>
                            <show_in_store>0</show_in_store>
                        </time>
                        <frequency translate="label">
                            <label>Frequency</label>
                            <frontend_type>select</frontend_type>
                            <source_model>adminhtml/system_config_source_cron_frequency</source_model>
                            <backend_model>mon_module/system_config_backend_cron</backend_model>
                            <sort_order>4</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>0</show_in_website>
                            <show_in_store>0</show_in_store>
                        </frequency>
                    </fields>
                </cron>
            </groups>
        </my_section>
    </sections>
    
+ Dans le Backend Model : Namespace_Monmodule_Model_System_Config_Backend_Cron

class Namespace_Monmodule_Model_System_Config_Backend_Cron extends Mage_Core_Model_Config_Data
{
    const CRON_STRING_PATH  = 'crontab/jobs/cron_task_identifier/schedule/cron_expr';
    const CRON_MODEL_PATH   = 'crontab/jobs/cron_task_identifier/run/model';

    /**
     * Cron settings after save
     *
     * @return Mage_Adminhtml_Model_System_Config_Backend_Log_Cron
     */
    protected function _afterSave()
    {
        $enabled    = $this->getData('groups/cron/fields/enabled/value');
        $time       = $this->getData('groups/cron/fields/time/value');
        $frequncy   = $this->getData('groups/cron/fields/frequency/value');

        $frequencyDaily     = Mage_Adminhtml_Model_System_Config_Source_Cron_Frequency::CRON_DAILY;
        $frequencyWeekly    = Mage_Adminhtml_Model_System_Config_Source_Cron_Frequency::CRON_WEEKLY;
        $frequencyMonthly   = Mage_Adminhtml_Model_System_Config_Source_Cron_Frequency::CRON_MONTHLY;

        if ($enabled) {
            $cronDayOfWeek = date('N');
            $cronExprArray = array(
                intval($time[1]),                                   # Minute
                intval($time[0]),                                   # Hour
                ($frequncy == $frequencyMonthly) ? '1' : '*',       # Day of the Month
                '*',                                                # Month of the Year
                ($frequncy == $frequencyWeekly) ? '1' : '*',        # Day of the Week
            );
            $cronExprString = join(' ', $cronExprArray);
        }
        else {
            $cronExprString = '';
        }

        try {
            Mage::getModel('core/config_data')
                ->load(self::CRON_STRING_PATH, 'path')
                ->setValue($cronExprString)
                ->setPath(self::CRON_STRING_PATH)
                ->save();

            Mage::getModel('core/config_data')
                ->load(self::CRON_MODEL_PATH, 'path')
                ->setValue((string) Mage::getConfig()->getNode(self::CRON_MODEL_PATH))
                ->setPath(self::CRON_MODEL_PATH)
                ->save();

            if (!empty($cronExprString)) {
                Mage::getSingleton('adminhtml/session')->addNotice(
                    Mage::helper('mon_module')->__('Cron Expression Set To [%s]', $cronExprString)
                );
            }
        }
        catch (Exception $e) {
            Mage::throwException(
                Mage::helper('mon_module')->__('Unable to save the cron expression.')
            );
        }
    }
}

+ Dans le Model Cron : 
class Namespace_Monmodule_Model_Cron
{
    const XML_PATH_CRON_ENABLED = 'my_section/cron/enabled';

    public function run()
    {
        if (!Mage::getStoreConfigFlag(self::XML_PATH_CRON_ENABLED)) {
            return $this;
        }
        
        .......
        $this->DoSomeStuff();
        .......
    }
}