Drupal 6 caching and blocks

Question

I've read all over the place and I'm trying to figure out if I am understanding the way caching happens in Drupal 6. We have a site that has a real time stock ticker in it. We have Drupal caching enabled so the stock price ends up getting cached and frozen at a specific spot. I figured a way I could handle it would be to put the ticker in a block I make in a custom module and set BLOCK_NO_CACHE, but if I'm understanding this correctly, if you have site caching enabled, then the ENTIRE page gets cached including any and all blocks on it regardless of their individual cache settings. Is this correct? So am I unable to take advantage of site caching then if I have certain spots that should not cache? Does anyone know of another solution I might be able to use to have the best of both worlds? To be able to have site caching, but also have a real time stock ticker? By the way, the stock ticker is making a JSON request to the Yahoo finance API to get the quote.

Answer 1

You are correct, the directive BLOCK_NO_CACHE is only applicable to block level. However when page caching is enabled then Drupal will cache the entire page (which includes the block as well). But this is only applicable to anonymous users. Drupal's philosophy is that the content for anonymous users is always the same so they get served the cached page. But this is not applicable to authenticated users. Since different users might have different access to certain parts of the page (e.g. the links block will look different for an admin than a regular user).

You might want to have a look at this discussion: BLOCK_NO_CACHE not working for anonymous users

And there is a solution, which you'll stumble upon this discussion. It's this module: Ajax Blocks. Extract from the module description:

Permits to load some blocks by additional AJAX request after loading the whole cached page when the page is viewed by anonymous user. It is suitable for sites which are mostly static, and the page caching for anonymous users is a great benefit, but there are some pieces of information that have to be dynamic.