One of CloudFlare features is the “Always Online” feature, it offers to your visitors a temporarily cached copy of your website for reading only, and if the visitor tried using any dynamic feature such as login or adding comments or something like that, the features will not work and the visitor will get an error, anyway this is better than the complete stop of the site.
When does “Always Online” feature work?
First the feature should be enabled for the domain, and at least 10 days had passed since it was enabled, after that if the server hosting your site stopped for any reason such as maintenance, the cached pages will be displayed during the temporarily stop of the server till it returns back to work.
How does “Always Online” feature work and how the pages are cached?
Before I go into the mechanism let us remember another thing Google Crawlers (Spiders) they scan your site and explore all the available pages, and add them to the search results (regardless of its display location or its order). This is not all, Google also makes a copy of the page which is known as “Cached Page”, Google crawlers browse the site as unknown visitor (unregistered), and so Google crawlers can’t access sensitive pages or data, and so there are no harm from the cached pages that Google makes since it is already appears to any human visitor browsing your site.
Fine, the same thing CloudFlare do, it has crawlers called “CloudFlare-AlwaysOnline” scans all the sited hosted by Dimofinf (the ones that enabled the “Always Online” feature) once every 9 days, and browses the site as an unknown visitor and makes a copy and store it in CloudFlare servers, and distribute it over more than 20 data centers around the world, and in case the server stopped working these pages start displaying to your site visitors until the server start working again.
These crawlers use User-Agent
Mozilla/5.0 (compatible; CloudFlare-AlwaysOnline/1.0; +http://www.cloudflare.com/always-online)
But some pages when accessed it appears that the site is not working
Yes this happens, Google does not index all the links of your site in the first visit, same thing with CloudFlare can’t make a copy of every page from the first visit, especially when your site contains a lot of pages this will need time, also every time you do “Cache Purge” you lose all the cache in CloudFlare servers and you return to step zero.