Image caching and cron jobs

Clooth

On my website, currently on another server due to high cpu load, I have a dynamic signatures system, which gets ALOT hits when I had it on my website, they were getting up to 2,000,000 hits a month, and then I had to take them down.

So what I'm asking is, how could I make the images cache into a folder, let's say a folder called 'sig', and insert a mysql record, then on an hourly basis, a cron job to run a php script to update all the signatures cached, with the new information, basically by removing all of them, or just re-creating.

The main signature file should only call the cached signature, if it has been created before, else create it in the folder, and show that.

If you need anything else to know, please ask.

Also if you really think you could help me with this, through MSN would be the best, add me at C@Zybez.net.

Thanks!

Nico

MarkR

Yes you could certainly do that. Also, caching the images on the client side could be effective too. If you're generating the file from PHP, then you should:

Not use sessions (don't call session_start) or anything else which sends "don't cache" headers.
Send a "Last-modified" header (ideally take this from the date/time it was modified)
Send an "Expires" header which is in the future (say 24 hours or more)
Optionally send some other headers to help the browser a bit.

This means that the client side (and/or proxies) will cache it. This is the best caching as it uses up none of your resources.

Mark

Clooth

But how could I update them?

MarkR

Once the image in the cache expires, the browser will request the object again. There is no way of telling it to get it earlier.

Set the "Expires" header to a reasonable time (but not too soon or you lose the benefit).

Mark

Clooth

Ok, I made the signature script to check if the image had been created before, since it works with 2 parameters, an username, and a background variable, then if the image does exist, it returns that from the 'cache' folder. else it creates it 's/background,username.png'.

Then I made another script, to read through the cache folder, parse the file names and call another script to re-create all of the images again, through the signature script, just as normal except without the checking if its created already, since it overwrites them with the new ones.

I'm just having problems thinking how I could call the scripts..in a loop.