Example: Application Load Balancing
1. Example: Application Load Balancing
Let me walk through an Application Load Balancer in action. The project on this slide has a single global IP address, but users enter the Google Cloud network from two different locations: one in North America and one in EMEA. First, the global forwarding rule directs incoming requests to the target HTTP proxy. The proxy checks the URL map to determine the appropriate backend service for the request. In this case, we are serving a guestbook application with only one backend service. The backend service has two backends: one in us-central1-a and one in europe-west1-d. Each of those backends consists of a managed instance group. Now, when a user request comes in, the load balancing service determines the approximate origin of the request from the source IP address. The load balancing service also knows the locations of the instances owned by the backend service, their overall capacity, and their overall current usage. Therefore, if the instances closest to the user have available capacity, the request is forwarded to that closest set of instances. In our example, traffic from the user in North America would be forwarded to the managed instance group in us-central1-a, and traffic from the user in EMEA would be forwarded to the managed instance group in europe-west1-d. If there are several users in each region, the incoming requests to the given region are distributed evenly across all available backend services and instances in that region. If there are no healthy instances with available capacity in a given region, the load balancer instead sends the request to the next closest region with available capacity. Therefore, traffic from the EMEA user could be forwarded to the us-central1-a backend if the europe-west1-d backend does not have capacity or has no healthy instances as determined by the health checker. This is referred to as cross-region load balancing. Another example of an Application Load Balancer is a content-based load balancer. In this case, there are two separate backend services that handle either web or video traffic. The traffic is split by the load balancer based on the URL header as specified in the URL map. If the user is navigating to /video, the traffic is sent to the backend video service, and if the user is navigating anywhere else, the traffic is sent to the web-service backend. All of that is achieved with a single global IP address.2. Let's practice!
Create Your Free Account
or
By continuing, you accept our Terms of Use, our Privacy Policy and that your data is stored in the USA.