Starting at around 06:00 AM CST, July 23, 2012 Dotcom-Monitor began to detect a higher than usual number of DNS-related errors. The errors were sporadic and happening in bursts every couple of hours.
We are still looking for a root cause, but we believe issue started with a DDoS on Zerigo DNS services. We have a large number of our clients using Zerigo for their DNS hosting. Zerigo took their servers down due to the DDoS DNS this morning: see http://zerigostatus.net.
As you are aware, as part of its monitoring Dotcom-Monitor does not cache any DNS queries and we do a fresh IP lookup each time we check a URL. Because Zerigo servers were not responding and requests were timing out, it increased our load exponentially on processes that provides DNS resolution. As result, we believe, some of our legit queries also resulted in timeout errors.
We have made few adjustments to the way DNS resolution is performed and we believe it resolved that specific issue, but we continue to closely review the numbers. The change on our side was completed around 2PM CST. If you are still receiving DNS errors, please login to your account and open a support ticket Support >Troubleticket for our team to address.
To login visit: www.dotcom-monitor.com/User/clients-login.aspx or click the button below.