I have a site where each time you upload an image it gets rendered in various frame sizes. A cron job runs every 10 minutes which looks to see if any new images have been uploaded during that time and if so it generates all the needed frames.
Since this cron runs every 10 minutes there is some time between the content (such as an article) goes live and the time the images are made available. So during that meantime a generic placeholder image with the site’s logo is shown.
Since Akamai caches an image, when a site user loads a page which has an image that hasn’t been rendered by the cron yet, then a static placeholder will show for that image path and Akamai will cache this. Even when the image is later rendered and is available users will still get the cached version from Akamai.
One solution is to bust the “ages” of these images when the cron has rendered them. But it takes Akamai about 8 min to come back for the new ones.
Is there any other solution where I can tell Akamai perhaps through cache expiration headers to come back every 10 seconds until a new image is received and once that’s done don’t come back again and keep showing the cached version?
Yes, in a way. If you combine a few steps from the server side and within the akamai settings.
Here’s the concept: the Edge Server delivers the content that it has. If you use cache-control headers, from php for example, the TTL settings in the akamai configuration settings of the respective digital property blow them away and it uses those instead. Meaning you tell it how often to come to your origin server by path, file type, extension, or whatever. Then from the client side, whatever files it has it delivers to the end user and it doesn’t really matter how often the Edge Servers get requested for the content unless you don’t cache at that level, rolling it back up to you.
Using those configuration settings you can specify that a specific file has an exact expiration – or to not cache it at all.
So if on the server side if you specify placeholder.jpg on your page and tell akamai not to cache that image at all, then it’ll come back each time the Edge Server gets a request for it. Once you have the image in place then placeholder.jpg doesn’t exist on your page any more and instead there is sizeA.jpg, which would obey regular image caching times.
This may not be exactly ideal, but it’s as best as you can do other than manually clearing the page and as far as I know they don’t have an API call to clear a page that you can fire off (plus it take 7-10 minutes for a cache-clear to propagate through their n/w anyway).