Imagine Amazon Route 53 as a city’s traffic control system that directs cars (internet traffic) to different streets (servers or resources) based on traffic conditions and road health (the health and configuration of your AWS resources).
Active-Active Failover
In an active-active scenario, you have two streets leading to your destination (your website or application), and both are open to traffic all the time. If one street gets blocked (a server fails), traffic simply continues flowing through the other street. This is useful when you want to balance the load between two resources that are always available.
Active-active failover gives you access to all resources during normal operation. In this example, both region 1 and region 2 are active all the time. When a resource becomes unavailable, Route 53 can detect that it’s unhealthy and stop including it when responding to queries.
Active-Passive Failover
In active-passive failover, you have one main street that you prefer all traffic to use (the primary resource) and a secondary street that’s only used if the main one is blocked (the secondary resource is activated only if the primary fails). This method is useful when you have a preferred resource to handle requests but need a backup in case it fails.
Use an active-passive failover configuration when you want a primary resource or group of resources to be available the majority of the time and you want a secondary resource or group of resources to be on standby in case all the primary resources become unavailable.
Configuring Active-Passive Failover with One Primary and One Secondary Resource
This approach is like having one big street and one small street. You use the big street whenever possible because it can handle more traffic or get you to your destination more directly. You only use the small street if there’s construction or a blockage on the big street.
Configuring Active-Passive Failover with Multiple Primary and Secondary Resources
Now imagine you have several big streets and several small streets. All the big ones are your preferred options, and all the small ones are your backup options. Depending on how many big streets are available, you’ll direct traffic to them before considering using the small ones.
Configuring Active-Passive Failover with Weighted Records
This is like having multiple streets leading to your destination, but you give each street a “weight” based on how often you want it used. Some streets (resources) are preferred more than others, and that preference is adjusted by weight. You still have a backup street for when your preferred options aren’t available.
Evaluating Target Health
“Evaluate Target Health” is like having traffic sensors that instantly tell you if a street is blocked. If you’re routing traffic to AWS resources for which you can create alias records, you don’t need to set up separate health checks for those resources. Instead, you enable “Evaluate Target Health” on your alias records, and Route 53 will automatically check the health of those resources. This simplifies setup and keeps your traffic flowing to streets (resources) that are open and healthy without needing additional health configurations.
In short, Amazon Route 53 offers a powerful set of tools that you can use to manage the availability and resilience of your applications through a variety of ways to apply failover configurations. Implementation of such knowledge into the practice of failover strategy will result in keeping your application up and available for the users in cases when any kind of resource fails or gets a downtime outage.
