Automatic failover and health checks for Cloudflare® sites

New settings to tune the website checks

To improve check stability you can tune your checks in the “Advanced settings” now by setting check interval length, open/read timeout and failback delay.

Check Interval

The default 10 seconds is too fast for some servers/check pages, adjust as needed. If your check is depending on server load (i.e. a search page) and takes 3-5 seconds, a 20 seconds interval is perhaps better.

Open/read timeout

Open timeout is reached when no connection can be made. Do not set this too low or the checks will not reach your server reliably. Check your dashboard for the milliseconds a check takes.

Read timeout can be low unless you are waiting for the search page data transfer from above.

As there can be only one check running at a time, these values have to make sense with the check interval time:

read-timeout + open-timeout + "some buffer" < check interval

Failback delay

This is the time the primary server has to be ok before failing back. Checks will remain in pending1 state until the time has passed. If the server fails again, the timer will restart.

Changing these values helps against state flapping where the checks are “too nervous” - so you receive a lot of CHECK FAILED!…check is ok notifications.

-Knut (founder