DNS Failover uses two of the applications in the Constellix suite: DNS and Sonar monitoring. First, we are going to create monitoring checks in Sonar and then apply those checks to failover records in the DNS control panel.
You can watch the full demo here:
In case you need a quick refresher, DNS Failover allows you to configure “backup” endpoints for your DNS records. For example, let’s say we have two web servers located at 18.104.22.168 and 22.214.171.124. The first web server is our primary, while the second is only used when the primary is unavailable. In this case, we would create an A record with failover and add both IP’s to the record in order of priority.
#1 Create a Check in Sonar
Jump to this tutorial to learn how to create a Sonar check.
#2 Clone the Check
Clone the check you just made by clicking the button in the upper right-hand corner of the check configuration screen.
Change the name and IP/FQDN values to match your secondary endpoint. Test the check and save.
Rinse and repeat for however many endpoints you want to include in the failover configuration.
#3 Switch to the DNS App
In the top left corner, click the menu button and select the DNS application.
In the sidebar click Managed DNS / Domains and select the domain you want to apply Failover to.
#4 Create Record
Create the appropriate record. For this example, we want to create an A record since we are pointing to an IP address.
Enable Failover in the Record Mode menu.
There are three failover settings you can choose from. Let’s say you have three endpoints called A, B, and C. This is how each setting would failover traffic to each with A being the primary and C being the tertiary.
A to B. If A is back up, then A. If both A and B are down, then C.
Off on Any Failover Event
A to B, then stops. Stays at B until failover is turned back on.
A to B to C, then stops.
Failover with Round Robin
You also have the option to combine failover with round robin, which is our load balancing service. That means each time the record is queried, a different endpoint would be returned. If we have three endpoints in the record, each endpoint has a 33% chance of being returned. If any of these endpoints are down, then they will be removed from the configuration.
Query 1: A
Query 2: B
Query 3: C
Query 4: A is down so B is returned
Query 5: C
Query 6: B
… and so on
Make sure you add your endpoints in order of priority, ie: the first row should be your primary endpoint.
Click Add Another IP to add another endpoint.
In the Sonar Check column, click the dropdown menu. Any monitoring checks that match the IP/FQDN in that row will appear in the dropdown. Choose the one you want to use with this check and in the Status column you will see the current status of the check.
When you are done adding the necessary endpoints and checks, Save your check and Commit your changes.
Your failover record will propagate instantly to all of our nameservers, so you can immediately query them in a terminal to make sure your record is live.
In the Records screen, you can see which IP/FQDN is being returned in the IP/Pool column with an asterisk.