Set up a managed instance group backend

Cloud CDN leverages Google Cloud global external Application Load Balancers to provide routing, health checking, and Anycast IP support. Global external Application Load Balancers can have multiple backend instance types, and you can choose which backends (or origins) to enable Cloud CDN for.

This setup guide shows you how to create a global external Application Load Balancer with a Compute Engine managed instance group backend with Cloud CDN enabled.

For general concepts, see the External Application Load Balancer overview.

If you are an existing user of the classic Application Load Balancer, make sure that you review Migration overview when you plan a new deployment with the global external Application Load Balancer.

Load balancer topologies

For an HTTPS load balancer, you create the configuration shown in the following diagram.

External Application Load Balancer with a managed instance group (MIG) backend.
Figure 1. External Application Load Balancer with a managed instance group (MIG) backend (click to enlarge).

For an HTTP load balancer, you create the configuration shown in the following diagram.

External Application Load Balancer with a managed instance group (MIG) backend.
Figure 2. External Application Load Balancer with a managed instance group (MIG) backend (click to enlarge).

The sequence of events in the diagrams are as follows:

  1. A client sends a content request to the external IPv4 address defined in the forwarding rule.

  2. The load balancer checks whether the request can be served from cache. If so, the load balancer serves the requested content out of cache. If not, processing continues.

  3. For an HTTPS load balancer, the forwarding rule directs the request to the target HTTPS proxy.

    For an HTTP load balancer, the forwarding rule directs the request to the target HTTP proxy.

  4. The target proxy uses the rule in the URL map to determine that the single backend service receives all requests.

  5. The load balancer determines that the backend service has only one instance group and directs the request to a virtual machine (VM) instance in that group.