GCP Managed Instance Groups

GCP's Managed Instance Groups (MIGs) are a kind of cluster of instances that are all usually spun up from the same instance templates and the same disk images. We usually use MIGs for High Availability and performance benefits (currently moving away from MIGs in favor of unmanaged IGs. We will return to MIGs later when we are ready for it).

Troubleshooting

Reserved IP address got unassigned from the instance group instance

You can bring back an unassigned reserved IP address from the VPC network ➝ IP addresses page. Simply click on the three dots for the IP address you want to reassign back to the resource:

All health checks failed after updating instance template

There's many reasons to this but one that we have come across is missing network tags for the instance after updating the instance template and replacing the instance. The Firewall section of the instance, where you can toggle checkboxes for: * Allow HTTP traffic * Alllow HTTPS traffic * Allow Load Balancer Health Checks give the instance a network tag: http-server , https-server or lb-health-check In our case the http-server network tag had dropped.