XML Fetcher Cron作业：运行频率和提取次数？

Question

I've got a PHP script on a shared webhost that selects from ~300 'feeds' the 40 that haven't been updated in the last half hour, makes a cURL request and then delivers it to the user.

SELECT * FROM table WHERE latest_scan < NOW() - INTERVAL 30 MINUTE ORDER BY latest_scan ASC LIMIT 0, 40;
// Make cURL request and process it

I want to be able to deliver updates as fast as possible, but don't want to bog down my server or the servers I'm fetching from (it's only a handful).

How often should I run the cron job, and should I limit the number of fetches per run? To how many?

Answer 1

It would be a good thing to "rate" how often each feed actually changes so if something has an average time of 24 hours per change, then you just fetch is every 12 hours.

Just store #changes and #try's and pick the ones you need to check... you can run the script every minute and let some statistics do the rest!