Me as well. It looks like the forum PHP code is having trouble connecting to the mysql database, as the error is being generated in response to a failed mysqli_real_connect() call.
The interesting question (to me) is why CloudFlare DDoS protection is kicking in. Maybe just as a result of the HTTP 503 & 520 errors that CloudFlare is seeing coming from the forum? But a real attack could certainly cause mysql connection issues simply due to concurrent connection limits, etc. Of it could be all the folks reloading the page trying to get it to work! Heh.