Fallback cache functionality

  • Resolved egravity

    (@egravity)


    3 years, 10 months ago

    Hi,

    Thanks for your amazing plugin. I just have a technical question about when Fallback Cache is supposed to generate a html document in the fallback_cache folder.

    I am monitoring a couple of sites with this feature enabled, but can’t seem to figure out what triggers fallback_cache to generate. The .tmp key files in cached_html_pages are generated as I would expect on a successful GET request when there is no Cloudflare cache present. But the HTML files in fallback_cache appear to show up at random, sometimes several hours apart and long after they appeared in cached_html_pages.

    Is this intended functionality? Do they only generate when Cloudflare cache expires or is invalidated? Or could there be a different technical issue with my installations?

    Thanks in advance.

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  • Plugin Contributor iSaumya

    (@isaumya)

    3 years, 10 months ago

    Hi,
    cached_html_pages and fallback_cache are two different functions. So, the cached_html_pages kicks in when you have enabled the option of Purging only HTML pages: https://i.imgur.com/evz08nZ.jpeg

    In this case when you purge cache for a page or when you update a content and the plugin starts purging cache for that page and related pages, instead of purging everything, i.e. the main HTML page requests + the static files of the page, instead it only purging the main URL that is HTML page. E.g. https://example.com/something-foo/.

    So, to facilitate that feature, the system needs to know all the page URLs that are cached in Cloudflare. So, the way it does is, when someone access a page for the first time and it is not yet cached in CF CDN, the plugin takes that URL of the request and put it in the cached_html_pages folder with a .tmp file.

    Also at this time, if you have fallback cache enabled, the plugin will also generate a disk level cache of the HTML page in the fallback cache folder. So, that in future if the cache expires and the request comes to the origin server, then instead of executing PHP the fallback cache and send the disk cached HTML.

    But if you have prefetch on hover or prefetch on viewport option enabled in the others tab of the plugin settings, at that time the prefetch request invoke Cloudflare to cache that page but fallback cache is not yet generated. So, when that cache expires and request comes to the origin server again – at that time the fallback cache is generated.

    I hope this clarifies your doubt and question.

    Also note that if you have a moderate traffic website with Cloudflare Smart Tiered Cache enabled in Cloudflare dashboard, you might not need the fallback cache and Cloudflare will keep the content cached for much longer time.

    To learn more about how Cloudflare cache works, check out: https://acnam.com/untold-truths-of-cloudflare-cdn/#cloudflare-cache-creation-replication-storage

Viewing 1 replies (of 1 total)

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