Magento related, can I change the cron job time interval with something new from my database?

Question

For example, I got in config,

<crontab>
    <jobs>
        <test>
            <schedule>
                <cron_expr>*/15 * * * *</cron_expr>
            </schedule>
            <run>
                <model>test/observer::saveAction</model>
            </run>  
        </test>
    </jobs>
</crontab>

And at: */15 * * * *, can I call a specific time from my db? I want to let the user choose the time interval for the update function. But I am not sure if I can call something from db using php in config.xml, is there a way to put the interval for a cron job in a php file?

Answer 1

You can create a system configuration text field via system.xml and use it as your cron schedule:

<crontab>
    <jobs>
        <test>
            <schedule>
                <config_path>path/to/system_config</config_path>
            </schedule>
            <run>
                <model>test/observer::saveAction</model>
            </run>  
        </test>
    </jobs>
</crontab>

Don't forget to add a default value to this field or it won't work if your customer don't change it:

<default>
    <path>
        <to>
            <system_config>*/15 * * * *</system_config>
        </to>
    </path>
</default>