3D FlipBook - Thumbnail cache issue when PDF changes
The problem is that the auto thumbnail .png filename is based on the post/page ID, which does not change. So every time the PDF is changed/swapped, the thumbnail filename does not change. For example, it stays as 120000.png. I just had to put special case rules for expiration in the apache config, but ideally the plugin should use a random filename when generating the thumbnail. If random is too hard, then maybe use the unix timestamp of the PDF file itself for the filename. The way it is currently coded, since the same filename is used, browsers may not see that the file changed and will use the cache expiration of the old thumbnail. On our site, that means 30 days.
( I replied to this old thread - https://3dflipbook.net/question?id=1906 - but maybe this software does not notify since I noticed it did not move the thread to the top of the question list )
there was no idea that pdf file will be often replaced. Usually user select it once and forget about it forever.
The customer publishes a monthly magazine. It is much easier for them to change the PDF each month on the same post rather than creating a new one. It makes their monthly workflow easier.
I realize perhaps you did not have that original idea, but that it how it is being used by at least one of your customers. It would be nice if you could fix that...as I suggested, I think it should be a fairly simple change of generating the thumbnail with something random whenever the post is updated/saved.