Since Cloudflare acts as a proxy, we can cache certain pages of your site. When your site goes down because of your server, we can continue to serve your visitor's page requests as long as the page is in our cache as part of our Always Online functionality (generally 1-3 pages). This ensures a seamless experience for your visitor. We continually check for your site to come back online and once it does, we switch back to the live version.
Always Online banner
If you are seeing the Always Online banner and your server is not offline, then something on your server or hosting provider's network is blocking or rate-limiting Cloudflare's requests.
Since Cloudflare acts as a reverse proxy, all connections to your server come from a Cloudflare IP. Since the same amount of traffic now comes from a smaller number of IPs, server-side security solutions can mistake the increase in connections from this smaller set of IPs as an attack, when they are legitimate.
- Make sure that you're not blocking Cloudflare IPs in .htaccess, iptables, or your firewall.
- Make sure your hosting provider isn't rate limiting or blocking IP requests from the Cloudflare IPs and ask them to whitelist the IP addresses found here: www.cloudflare.com/ips
- Make sure that you're operating off of the most recent versions of Bad Behavior or mod_security. You want to ensure that mod_security's core rules aren't blocking Cloudflare requests.
- If you are running custom Apache modules, such as mod_antiloris and mod_reqtimeout, disable and unload the modules. These modules will block any time an IP that connects more than 22 times. Since all connections are now coming from a Cloudflare IP, you will definitely hit the limit causing the error page. As soon as you unload the module, the issue will disappear.
There are limitations to the Always Online service. The limitations are outlined in detail here.