마이크로서비스 소개 pt. 4

So far, we've implemented an API Gateway that receives all the requests and routes them accordingly. Also, our services/instances are registered with our Service Registry and the Gateway checks the service's location with it. But how can we make so that our Gateway uses all available instances of a service and no instance becomes overloaded?

To insure that, we need to implement a Load Balancer. This pattern will leverage the requests between available instances of our services. Ocelot gives us a simple way to implement a Load Balancer. Also, it provides a few different algorithms of load balancing:

1. Round Robin - Imagine that you have three instances of a given service. The algorithm will make so that the first request is handled by instance #1, the second by instance #2, the third by instance #3, the fourth by #1 again, and so on;
2. Least Connections - Every new request is sent to the instance with the least amount of active connections;
3. Cookies Sticky Sessions - Uses a cookie to direct all request to a specific instance.

IMPORTANT: Keep in mind that other load balancing solutions might have different algorithms.

To implement our Load Balancer, Ocelot makes it very easy. All we need to do is add a new property to our 'ocelot.json' file. This property needs to be added on a route per route basis:

{
  "Routes": [
    {
      // ...
      "LoadBalancerOptions": {
        "Type": "RoundRobin"
      }
    },
    {
      // ...
    }
  ],
  // ..
}

That's it! Our API Gateway can now balance the load between all of our services instances!

On the next article, we'll talk about the pattern. Until next time.