How to apply label to instances of Managed Instance Group

For a managed group with auto-scaling enabled you should design or retrofit your application so that it is independent of specific instance properties that will not persist such as IP address or in-memory data. This is due to the stateless nature of the managed group as described in this document.

In such case, new instances can be created and others recreated following the configured instance template. For example, once utilization ( can be other set metric) decreases it should destroy unused instances and recreates new instance with changed IP addresses. Instances within managed groups are intended to be dynamically re-created, they get created from the instance template. That being said, due to the stateless nature of the managed group with auto-scaling enabled, even though you create instances with static IP it gets change every time with the auto-scaling operation.

This is usually a problem with your instance template. It happens to me occasionally when I make a new template and apply it where my instance will sit there spinning forever saying instance is being verified. Revert to an older template if you can (or make a new one from an instance snapshot) and replace the instance.