[development] estimating execution time left and hook_cron

[nitin gupta]

Hello,
I am maintaining the module feedapi imagegrabber, which pulls the images
from the original url of the feed items (just like google reader). It is
implemented on the top of feedapi and hence implements the
feedapi_after_refresh() hook, which is basically fired by the feedapi after
it has refreshed the feed.

Now, as my module download images from an external website, I can never be
sure about the time it will take to complete the job of downloading images
for all the feed items. Therefore, sometimes I get a 'fatal execution time
exceeded error'. How can I know how much execution time is left, so that I
can return on time by saving the rest of the work as a cron job?

I have gone through the source code of FeedAPI which implements hook_cron().
It uses a variable called 'cron_semaphore', which I am guessing is some way
to share execution time but am unable to get how. I will really appreciate
if someone can explain the above to me or provide some tutorial links on
writing a good hook_cron implementation.

--
Regards,
Nitin Kumar Gupta
http://publicmind.in/blog/
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