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CronThis table is named after the time-based job scheduler in Unix-like computer operating systems. It lists jobs (~tasks), scheduled to run periodically at certain times or dates. The tasks can be related to system maintenance, security checks, log processing, or any user action needed to be performed on a regular (~periodic) fashion. Please, notice that this table has to do with scheduling and logging of preexisting zoglair plugins, classified as tasks (see below). So, although you are free to create as many rows you want here, you won't be able to code new functionality - you have to select an existing one. The cron form contains the following fields: [Main]
Notice: All time fields above, share a common syntax:
[Code] A text area, used for supplying task-specific parameters. [Log] A text area, used for logging task activity. You are free to edit and/or clear it. Please, keep in mind...There is a great difference between:
The real scheduler runs constantly, watching the clock, and executes tasks in parallel. This is its job. Zoglair does not run constantly. It only runs whenever a visitor requests a resource from your site. As soon as it serves that resource, it dies. This is the nature of HTTP. Additionally, the real scheduler caches the scheduled jobs into memory (since it never stops running). Zoglair cannot do that. It has to load them from the database, at all times. So, we have two issues here, that need to be addressed: accuracy and performance.
For the first issue (accuracy), zoglair cannot do much... If you have a busy site, working 24/7/365, then you will be fine. But if your site has no traffic, at the exact time one or more tasks are scheduled for execution, then they will be postponed. As soon as a request is made, they will be executed. Normally, this situation should not be a problem. Zoglair has no time-critical tasks, on its own. It won't matter if they run a few minutes, even hours, later. But, if there are other tasks that you have installed yourself, and their scheduled times are critical, then you should use the scheduler of your operating system to run them. All that is needed is a request to the following URL:
For example, on a Linux machine, you could add the following entry in
As for the second issue (performance), zoglair uses a simple but effective trick to trigger its internal mechanism that queries, runs and reschedules jobs. It places an invisible (zero width and height) image at the bottom of the HTML page (with the path shown above), which forces the browser to make a separate request, after the page is already rendered. For even better performance and less burden to the server, that image is not injected in every page delivered, but periodically, based on the |