On 05/26/2012 08:52 AM, Paul Moore wrote:
I am writing a macro that performs a relatively expensive calculation to generate content for display (a PNG image) based on user input. The basic macro works fine, but I'd like to cache the generated content to save recalculating it when I don't need to.
My idea is that I generate a SHA1 digest of the macro content, and persistently cache the output generated for that input. I'm thinking of using an LRU cache to avoid keeping massive amounts of data that'll never get used again. The question I have is where I can put the cache so that it is saved with the page, and I can access and update it from the macro code. I suspect that the answer is to attach an object to the page somehow, but I've been looking round the documentation and can't find any examples of how I might do this (TBH, I'm struggling to find my way round the documentation, so it may be that I've missed something obvious - if so, then by all means point me to the right place :-))
As the object is a PNG image, I'm currently base64-encoding it, and using a data URL to display it. But if it's possible to cache the data in such a way that the raw data is (or can be made) directly addressible via a URL, that would be even better.
Can anyone help?
Thanks, Paul.
Some resources that you can use: https://github.com/xwiki/xwiki-platform/blob/master/xwiki-platform-core/xwik... is the proper way of creating caches. You declare an @Inject dependency on that, then use the createNewCache method (if you don't plan on running a cluster, or don't think that the cached resources should be shared inside a cluster, then it's slightly better for performance to call createNewLocalCache). You can then use this cache to store some entries. https://github.com/xwiki/xwiki-commons/blob/master/xwiki-commons-core/xwiki-... is going to give you the location of the temporary storage directory. Combine this with https://github.com/xwiki/xwiki-platform/blob/master/xwiki-platform-core/xwik... and you have a nice way of serving image files stored on the disk to the HTTP client. Unfortunately, this way you have to implement your own LRU functionality and make sure you clean up files, otherwise you'll keep filling up the disk with temporary files. -- Sergiu Dumitriu http://purl.org/net/sergiu/