Background: I am implementing a custom cache handler in PHP. The cache script is triggered on-demand by website traffic. I want to intelligently handle an influx of simultaneous requests. To do this, I'm using the first request to trigger the cache writer. Concurrent requests are be deferred until after the cache is built. I welcome debates regarding this approach, but I still want an answer to my actual question below.
Question: I'd like to know the best method to defer loading of webpage content. Here are two options I'm considering.
Option 1: Delay the response server-side. I don't like this option because I could end up having hundreds of sleeping connections, and I don't think hosts would like that.
<?php while (!file_exists($cache)) sleep(1);
Option 2: Reload the page client-side. I don't like this option because the requests could be doubled, or trippled, depending on how long it takes to build the cache. With this I'm also worried about SEO Optimization. Will bots retry the page? Will they try more than once if the page still isn't ready?
Maybe there's another best approach?