There are several issues that can prevent amanaged instance group (MIG)from successfully creating or recreating a VM instance.

If logs are generated for a deleted MIG

The problem might be related to the following situations.

Attached autoscaler still exists

If youdeleteda MIG using the Compute Engine API and you did not issue a separate requestto delete the attached autoscaler, the Logs Explorer might show logs withthe following message.

The resource 'projects/PROJECT/zones/ZONE/instanceGroupManagers/DELETED_INSTANCE_GROUP_NAME' was not found.

Resolution:

To resolve this issue, delete the attached autoscaler using the Compute Engine APImethods:

• For an autoscaler of a zonal MIG, use theautoscalers.delete method.
• For an autoscaler of a regional MIG, use theregionAutoscalers.delete method.

If your MIG cannot create or recreate instances

The problem might be related to the following situations.

The boot disk already exists

By default, a new boot persistent disk is created when you create an instance.The name of the boot disk matches the name of the VM. If you name a VMmy-instance, the disk is also namedmy-instance. If a persistent diskalready exists with that name, the request fails. To resolve this issue, youcan optionallytake a snapshot, andthen delete the existing persistent disk.

The instance template is not valid

If you updated your instance template recently, there could be an invalidproperty that causes the MIG to fail VM creation. Examine theproperties for these common errors:

• You specified a resource that doesn't exist, such as a source image.
• You misspelled a resource name.
• You tried to attach an existing non-boot persistent disk in read/writemode but your group contains more than one VM. For groups with more than oneVM, any additional disks you want to share between all of the VMs in thegroup can be attached only in read-only mode.

Limit exceeded for resource type

The following error occurs when you try to create more than 2,000 VMs in aregional MIG or more than 1,000 VMs in a zonal MIG. You have reached the sizelimit for your instance group.

Error message:

ERROR: (gcloud.compute.<INSTANCE_GROUP_TYPE>.<METHOD>) Could notfetch resource: - Exceeded limit 'MAX_INSTANCES_IN_INSTANCE_GROUP' on resource 'PROJECT_ID'. Limit:NUMBER

Resolution:

To resolve this issue, try one of the following:

• If you are using a zonal MIG, use aregional MIGinstead.
• Create multiple MIGs and split your workload across them—for example byadjusting yourload balancingconfiguration.
• If you still need a bigger group, you canincrease the size limit of your MIG orcontact support to make a request.

If you cannot delete your MIG or its instances

The problem might be related to the following situation.

Resource not found in zone or region

The following error occurs when you try to delete a regional MIG and youspecify the--zone flag, specify no region, or specify the wrong region.A similar error can occur if you try to delete a zonal MIG and you specifythe--region flag.

Error message:

• ERROR: (gcloud.compute.instance-groups.managed.delete) Some requests did not succeed:‐ The resource 'projects/PROJECT/zones/ZONE/instanceGroupManagers/INSTANCE_GROUP_NAME' was not found

• ERROR: (gcloud.compute.instance-groups.managed.delete) Some requests did not succeed:‐ The resource 'projects/PROJECT/regions/REGION/instanceGroupManagers/INSTANCE_GROUP_NAME' was not found

Resolution:

To resolve this issue, try one of the following:

• Append the appropriate--region or--zone flag to your command
• Set a default region and zone

Resource is used by a backend service

You cannot remove an instance group when it is used by a load balancer's backend service.You must remove the instance from the backend service before you can delete theinstance group.

Error message:

• ERROR: (gcloud.compute.instance-groups.managed.delete) Some requests did not succeed:‐ The instance_group_manager resource 'projects/PROJECT/zones/ZONE/instanceGroupManagers/INSTANCE_GROUP_NAME is already being used by 'projects/PROJECT/global/backendServices/BACKEND_SERVICE

• ERROR: (gcloud.compute.instance-groups.managed.delete) Some requests did not succeed:‐ The instance_group_manager resource 'projects/PROJECT/regions/REGION/instanceGroupManagers/INSTANCE_GROUP_NAME is already being used by 'projects/PROJECT/global/backendServices/BACKEND_SERVICE

Resolution:

1. Optional: Drain the backend instance group.

   • Forproxy load balancers only,you can set thecapacity scalerto0.0 before removing the instance group from a backend service. You canset the capacity scaler to zero by using thegcloud compute backend-services edit command.

   • For both proxy and pass-through load balancers, if youenable connection drainingon the backend service, Google Cloud attempts to allow existingconnections to persist, complete, and drain whenever an instance group isremoved from a backend service.

2. Remove the MIG from the regional or global backend service.

   • For a zonal MIG, run the following command:

     gcloud compute backend-services remove-backendBACKEND_SERVICE \    --instance-group=INSTANCE_GROUP_NAME \    --instance-group-zone=ZONE \    [--region=REGION | --global]

   • For a regional MIG, run the following command:

     gcloud compute backend-services remove-backendBACKEND_SERVICE  \    --instance-group=INSTANCE_GROUP_NAME \    --instance-group-region=REGION \    [--region=REGION | --global]

3. Delete the MIG:

   gcloud compute instance-groups managed deleteINSTANCE_GROUP_NAME

If your MIG continually tries to recreate instances

The problem might be related to the following situation.

Health check probes cannot reach the instance

If you configured an autohealing policy but you did not configure—ormisconfigured—the firewall rule that lets the health check probes reach yourapplication, then your VMsappear unhealthy,and the MIG continuously tries to recreate them. For information about how toconfigure a health check firewall rule, seeExample health check set up.