This document describes how to view the instance flexibility configuration in a
managed instance group (MIG) and the machine types used by each VM in the group.
After you add or make changes to instance flexibility in a MIG, you can do the
following:
- [View the instance flexibility configuration](https://docs.cloud.google.com/compute/docs/instance-groups/view-instance-flexibility-configuration#view_the_instance_flexibility_configuration)
to verify if a configuration has been applied or to check if a MIG already has
instance flexibility.
- [View the machine types used by each VM](https://docs.cloud.google.com/compute/docs/instance-groups/view-instance-flexibility-configuration#view_the_machine_types_used_by_each_vm)
to make sure that the machine type that you want to remove from an instance
selection is not used by any VM or to check the different machine types used
in the MIG.
- [Monitor live runtime VM distributions](https://docs.cloud.google.com/compute/docs/instance-groups/view-instance-flexibility-configuration#monitor_live_runtime_vm_distributions)
across machine types and zones to observe and potentially identify
improvements for your selected ranks and machine types.
## Before you begin
- If you haven't already, set up [authentication](https://docs.cloud.google.com/compute/docs/authentication). Authentication verifies your identity for access to Google Cloud services and APIs. To run code or samples from a local development environment, you can authenticate to Compute Engine by selecting one of the following options:
Select the tab for how you plan to use the samples on this page:
### Console
When you use the Google Cloud console to access Google Cloud services and
APIs, you don't need to set up authentication.
### gcloud
1.
[Install](https://docs.cloud.google.com/sdk/docs/install) the Google Cloud CLI.
After installation,
[initialize](https://docs.cloud.google.com/sdk/docs/initializing) the Google Cloud CLI by running the following command:
```bash
gcloud init
```
If you're using an external identity provider (IdP), you must first
[sign in to the gcloud CLI with your federated identity](https://docs.cloud.google.com/iam/docs/workforce-log-in-gcloud).
> [!NOTE]
> **Note:** If you installed the gcloud CLI previously, make sure you have the latest version by running `gcloud components update`.
2. [Set a default region and zone](https://docs.cloud.google.com/compute/docs/gcloud-compute#set_default_zone_and_region_in_your_local_client).
### REST
To use the REST API samples on this page in a local development environment, you use the
credentials you provide to the gcloud CLI.
1. [Install](https://docs.cloud.google.com/sdk/docs/install) the Google Cloud CLI.
2. If you're using an external identity provider (IdP), you must first [sign in to the gcloud CLI with your federated identity](https://docs.cloud.google.com/iam/docs/workforce-log-in-gcloud).
For more information, see
[Authenticate for using REST](https://docs.cloud.google.com/docs/authentication/rest)
in the Google Cloud authentication documentation.
## View the instance flexibility configuration
### Console
1. In the Google Cloud console, go to the **Instance groups** page.
[Go to Instance groups](https://console.cloud.google.com/compute/instanceGroups)
2. In the **Name** column, click the name of the MIG of which you want to
view the instance flexibility configuration.
The overview page of the MIG opens.
3. Click the **Details** tab.
In the **Instance flexibility** section, the **Instance selections**
table shows the instance selection name, rank, and the machine types in
a selection. If the MIG doesn't have instance flexibility configured, the
**Instance flexibility** section is not shown.
### gcloud
To view the instance flexibility configuration, use the
[`instance-groups managed describe` command](https://docs.cloud.google.com/sdk/gcloud/reference/compute/instance-groups/managed/describe).
Include the `--format` flag to filter the
`instanceFlexibilityPolicy.instanceSelections` properties.
```
gcloud compute instance-groups managed describe INSTANCE_GROUP_NAME \
--region REGION \
--format="json(instanceFlexibilityPolicy.instanceSelections)"
```
The following is a sample output:
```
{
"instanceFlexibilityPolicy": {
"instanceSelections": {
"instance-selection-1": {
"machineTypes": [
"n1-standard-16",
"n2-standard-16",
"e2-standard-16"
],
"rank": 1
}
}
}
}
```
If a MIG doesn't have instance flexibility configured, the output returns
`null`.
Replace the following:
- `INSTANCE_GROUP_NAME`: the name of the MIG of which you want to view the instance flexibility configuration.
- `REGION`: the region where the MIG is located.
### REST
To view the instance flexibility configuration, use the
[`regionInstanceGroupManagers.get` method](https://docs.cloud.google.com/compute/docs/reference/rest/v1/regionInstanceGroupManagers/get).
Include the `fields` parameter in the request URL to filter the
`instanceFlexibilityPolicy.instanceSelections` properties.
```
GET https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/instanceGroupManagers/INSTANCE_GROUP_NAME?fields=instanceFlexibilityPolicy.instanceSelections
```
The following is a sample output:
```
{
"instanceFlexibilityPolicy": {
"instanceSelections": {
"instance-selection-1": {
"machineTypes": [
"n1-standard-16",
"n2-standard-16",
"e2-standard-16"
],
"rank": 1
}
}
}
}
```
If a MIG doesn't have instance flexibility configured, the output returns
`null`.
Replace the following:
- `PROJECT_ID`: your [project ID](https://docs.cloud.google.com/resource-manager/docs/creating-managing-projects#identifying_projects).
- `REGION`: the region where the MIG is located.
- `INSTANCE_GROUP_NAME`: the name of the MIG of which you want to view the instance flexibility configuration.
## View the machine types used by each VM
### Console
1. In the Google Cloud console, go to the **Instance groups** page.
[Go to Instance groups](https://console.cloud.google.com/compute/instanceGroups)
2. In the **Name** column, click the name of the MIG in which you want view
the machine types used by each VM.
The **Overview** page of the MIG opens, which lists all VMs in the group,
their machine types, and other details.
### gcloud
To view the machine types used by each VM in a MIG, list the VMs using the
[`instance-groups managed list-instances` command](https://docs.cloud.google.com/sdk/gcloud/reference/compute/instance-groups/managed/list-instances) and include the `--format` flag to filter the
`propertiesFromFlexibilityPolicy.machineType` field. You can also filter
other fields as needed.
```
gcloud compute instance-groups managed list-instances INSTANCE_GROUP_NAME \
--region REGION \
--format='(name,instanceStatus,currentAction,propertiesFromFlexibilityPolicy.machineType,lastAttempt.errors.errors)'
```
The following is a sample output:
```
NAME: example-mig-0md2
STATUS: RUNNING
ACTION: NONE
MACHINE_TYPE: n1-standard-16
LAST_ERROR:
NAME: example-mig-vbgg
STATUS: RUNNING
ACTION: NONE
MACHINE_TYPE: n1-standard-16
LAST_ERROR:
```
Replace the following:
- `REGION`: the region where the MIG is located.
- `INSTANCE_GROUP_NAME`: the name of the MIG of which you want to view the instance flexibility configuration.
### REST
To view the machine types used by each VM in a MIG, list the VMs using the
[`listManagedInstances` method](https://docs.cloud.google.com/compute/docs/reference/rest/v1/regionInstanceGroupManagers/listManagedInstances)
and check the `propertiesFromFlexibilityPolicy.machineType` field in the
response.
```
POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/instanceGroupManagers/INSTANCE_GROUP_NAME/listManagedInstances
```
The following is a sample output; look for the
`propertiesFromFlexibilityPolicy` field in which the `machineType` field of
a VM is set.
```
{
"managedInstances": [
{
"instance": "https://www.googleapis.com/compute/v1/projects/example-project/zones/us-central1-b/instances/example-mig-0md2",
"instanceStatus": "RUNNING",
"id": "2656095434923471959",
"version": {
"instanceTemplate": "https://www.googleapis.com/compute/v1/projects/example-project/global/instanceTemplates/example-instance-template"
},
"targetStatus": "RUNNING",
"name": "example-mig-0md2",
"propertiesFromFlexibilityPolicy": {
"machineType": "n1-standard-16"
}
},
{
"instance": "https://www.googleapis.com/compute/v1/projects/example-project/zones/us-central1-b/instances/example-mig-vbgg",
"instanceStatus": "RUNNING",
"currentAction": "NONE",
"id": "9171259522409694366",
"version": {
"instanceTemplate": "https://www.googleapis.com/compute/v1/projects/example-project/global/instanceTemplates/example-instance-template"
},
"targetStatus": "RUNNING",
"name": "example-mig-vbgg",
"propertiesFromFlexibilityPolicy": {
"machineType": "n1-standard-16"
}
}
]
}
```
Replace the following:
- `PROJECT_ID`: your [project ID](https://docs.cloud.google.com/resource-manager/docs/creating-managing-projects#identifying_projects).
- `REGION`: the region where the MIG is located.
- `INSTANCE_GROUP_NAME`: the name of the MIG of which you want to view the instance flexibility configuration.
## Monitor instance distribution
While checking your static instance flexibility policy and listing individual VM
machine types provides a snapshot of your current configuration, observing how
your MIG allocates capacity over time requires real-time monitoring.
To verify that your VMs are distributed across your intended ranks and locations
when demand or capacity shifts, you can view the runtime instance distribution
for a specific MIG or aggregated data across multiple MIGs. For instructions on
how to view the instance distribution,
see [Monitor instance distribution in MIGs](https://docs.cloud.google.com/compute/docs/instance-groups/monitor-instance-distribution).
## What's next
- [Monitor instance distribution in MIGs](https://docs.cloud.google.com/compute/docs/instance-groups/monitor-instance-distribution).
- [Change or remove instance flexibility configuration](https://docs.cloud.google.com/compute/docs/instance-groups/change-or-remove-instance-flexibility-configuration).
- If your MIG doesn't have instance flexibility, [add instance flexibility](https://docs.cloud.google.com/compute/docs/instance-groups/configure-instance-flexibility).