Paid DNS Check accounts have the ability to monitor custom name servers. Up to this point, each DNS record group has been limited to a single custom name server. This has meant that if you wanted to monitor multiple name servers, you would have to create a DNS record group for each.
Today we’ve increased the number of custom name servers that a DNS record group can have from 1 to 10.
What should a DNS monitoring service do when it’s configured to check multiple name servers, and provide a single pass/fail result? Here’s what we came up with:
When multiple custom name servers are specified, DNS Check will randomize the order, then query them one by one until it receives a result. If the first response contains the expected record, the check passes. If the first response contains an error, or a different record than what was expected, the check fails.
If a query receives no response within 5 seconds, then DNS Check will query the next name server in its randomized list. Note that we may adjust this timeout, or make it configurable in the future. 5 seconds is a long time to have to wait for a response to a DNS query.
This means that if one of your name servers stops responding to queries entirely, DNS Check will move onto the next name server, and will not alert you about the issue unless it’s unable to communicate with any of your custom name servers.
If you wish to be notified if any one of your name servers aren’t reachable, then you should continue to specify a single name server per DNS record group.
We’re excited to make this new functionality available, and are already thinking of ways to improve it. For example, we may make the 5 second query timeout mentioned above configurable, or add in an option to check all name servers, and report on issues encountered with any of them.
Feel free to send in a feature request if you have any suggestions for improvement.