Google Cloud Platform for Developers

Failover ratio and backup pools

Building on health checks, a target pool may be configured with a failover ratio and backup pool. The failover ratio is calculated by the number of healthy instances in a target pool divided by the total number of instances, specified as a value from zero to one. Should the target pool's failover ratio be reached, traffic will be diverted to the backup pool. The backup pool here is a second target pool, with its own set of member instances. A target pool may only contain a single backup pool, and nested backup pools are not supported. Note that backup pools are not compatible with autoscaling via managed instance groups, a topic covered in later sections.

When deploying changes to backend instances, consider ...