I recently deployed an Octopress blog (which is a blogging platform built around Jekyll). It's a static-site blog generator, with no dynamic content or databases to muck about with. It's being served up by nginx.

My question is, what is the appropriate expires directive or Cache-Control header that I should set to make sure that visitors get the most up-to-date version of the site when they visit without having to manually refresh? Since the site is just .html files it seems to get cached pretty aggressively. I've tried a million different combinations of expires modified + xxxx and even straight up expires off but I can't seem to wrap my head around it. I'm very new to dealing with caching like this, specifically, on static files that change frequently, and obviously if the site hasn't been changed then I'd like for it to be served up out of the cache.

Update (still not solved though):

I found open_file_cache, tweaked that. Still no dice. It seems like what I might want to do is use nginx as a proxy cache and use Apache with ETags? Is there really no convenient way to make nginx play nicer with conditional requests from the client?

TL;DR: I'm running a static-file blog and I'd like to set up nginx to only serve from the cache if the blog hasn't been updated recently, but I'm too stupid to figure it out myself because I'm relatively new to web servers.