After you've created a managed instance group (MIG), you might want to add or remove VMs from that group to meet your workload's needs. If you have reached the default limit for the maximum number of VMs that you can add to a MIG, and you need more VMs, you can increase the size limit of the MIG.
To add or remove VMs in a MIG, you can do the following:
- Automatically add or remove VMs by setting the target size of the MIG:
- Use autoscaling for stateless applications
- Manually set the size of the MIG
- Manually add, remove or abandon specific instances:
Before you begin
-
If you haven't already, set up authentication.
Authentication is
the process by which your identity is verified for access to Google Cloud services and APIs.
To run code or samples from a local development environment, you can authenticate to
Compute Engine as follows.
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
-
Install the Google Cloud CLI, then initialize it by running the following command:
gcloud init
- Set a default region and zone.
Terraform
To use the Terraform samples on this page in a local development environment, install and initialize the gcloud CLI, and then set up Application Default Credentials with your user credentials.
- Install the Google Cloud CLI.
-
To initialize the gcloud CLI, run the following command:
gcloud init
-
Create local authentication credentials for your user account:
gcloud auth application-default login
For more information, see Set up authentication for a local development environment.
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.
Install the Google Cloud CLI, then initialize it by running the following command:
gcloud init
For more information, see Authenticate for using REST in the Google Cloud authentication documentation.
-
Set the group's target size
You can set a MIG's target size automatically by using an autoscaler or set the size manually.
Automatically adding and removing VMs in a MIG
You can configure managed instance groups to automatically add or remove VMs based on their workloads. Your applications can gracefully handle increases in traffic, and you can reduce your costs when the need for compute resources is lower. To start scaling your managed instance groups, see Create a MIG with autoscaling.
For more information, see Autoscaling groups of instances.
Manually setting the size of a MIG
If a managed instance group is not already set to
automatically scale, you can resize the group
manually to change the number of instances. If you increase the
size, the managed instance group uses the current instance template to add new
instances. If you decrease the size, the managed instance group deletes
VMs from the group. The group deletes instances with a
currentAction
of DELETING
, CREATING
, and RECREATING
before it deletes instances that are
running with no scheduled actions.
If the group is part of a backend service that has enabled connection draining, it can take up to an additional 60 seconds after the connection draining duration has elapsed before the VM instance is removed or deleted.
Console
In the Google Cloud console, go to the Instance groups page.
Under the Name column of the list, click the name of the instance group where you want to change the group size.
Click Edit to modify this managed instance group.
Under Number of instances, specify the number of instances that you want to include in this managed instance group. If Autoscaling is enabled, the group is automatically adding or removing instances as necessary. However, you can change the Minimum number of instances and the Maximum number of instances values to indirectly adjust the group size through Autoscaler.
Click Save to apply the new template.
gcloud
Use the resize
command.
gcloud compute instance-groups managed resize INSTANCE_GROUP_NAME \ --size NEW_SIZE \ --zone ZONE
REST
Call the resize
method for a
zonal
or
regional
MIG resource. Specify the new instance group size as a parameter.
POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instanceGroupManagers/INSTANCE_GROUP_NAME/resize?size=NEW_SIZE
If the instance group is a regional managed instance group, replace
zones/ZONE
with regions/REGION
.
After you make a request to resize a managed instance group, the VMs start or stop as soon as the system can provision or delete them. This process can take a significant amount of time depending on the number of instances in the group. Verify the status of instances in your managed instance group.
Disabling creation retries mode during resize
By default, if the initial creation of a VM instance fails, the managed instance group continuously retries to create the VM, until the VM is successfully created. However, if you do not want automatic creation retries, you can disable the creation retries mode when you resize the instance group. In this mode, the managed instance group attempts to create all instances only once. If there is an error during instance creation, the managed instance group gives up on this instance, removes it from the group's list of managed instances, and decreases the target size of the managed instance group.
This mode applies only during the first creation attempt of a VM. If a VM is created successfully while this mode is enabled, the VM behaves the same way as all other VMs created with a regular resize request. In particular, if a running VM dies unexpectedly at a later time and needs to be recreated, this mode does not affect the recreation behavior in that scenario.
Disabling the creation retries mode is especially useful in scenarios where you have systems automatically creating groups of VMs where an exact number of VMs is not required. You might prefer to stabilize quickly on the size of the managed instance group and be flexible in the number of VMs in the group, rather than to wait indefinitely until all the requested instances are created, which might be delayed temporarily or permanently because of quota errors or other unrelated issues.
Limitations
- You cannot disable creation retries for a regional MIG with an
EVEN
target distribution shape. - For regional MIGs with a
BALANCED
orANY_SINGLE_ZONE
target distribution shape, you must disable proactive instance redistribution before you can disable creation retries mode. - You cannot disable creation retries for autoscaled MIGs.
To resize a managed instance group when creation retries mode is disabled, use the Google Cloud CLI or REST.
gcloud
Use the beta resize
command
with the --no-creation-retries
flag.
gcloud beta compute instance-groups managed resize INSTANCE_GROUP_NAME \ --size NEW_SIZE \ --no-creation-retries \ [--region REGION | --zone ZONE]
Replace the following:
INSTANCE_GROUP_NAME
: The name of the MIG that you want to resize.NEW_SIZE
: The target number of running instances in managed instance group.ZONE
: For zonal MIGs, the zone where the MIG is located.REGION
: For regional MIGs, the region where the MIG is located.
REST
For a zonal MIG, use the
beta instanceGroupManagers.resizeAdvanced
method
or, for a regional MIG, use the
beta regionInstanceGroupManagers.resizeAdvanced
method.
Specify the new group size and the noCreationRetries
field in the request
body.
For example, make the following call to resize a zonal MIG with creation retries mode disabled.
POST https://compute.googleapis.com/compute/beta/projects/PROJECT_ID/zones/ZONE/instanceGroupManagers/INSTANCE_GROUP_NAME/resizeAdvanced { "targetSize": NEW_SIZE, "noCreationRetries": true }
Replace the following:
PROJECT_ID
: Your project ID.ZONE
: The zone where the MIG is located. For a regional MIG, replacezones/ZONE
withregions/REGION
and specify the region. For more information, see About regional MIGs.INSTANCE_GROUP_NAME
: The name of the MIG that you want to resize.NEW_SIZE
: The target number of running instances in the managed instance group.You can see which instances are being created and in which mode by using the
listManagedInstances
method. When the creation retries mode is disabled, instances that you create have acurrentAction
ofCREATING_WITHOUT_RETRIES
.
Add, remove or abandon specific instances
Creating instances with specific names in MIGs
If you have a system that depends on specific names, you can add VMs with specific names to an existing MIG.
The names that you assign to these managed instances persist if the MIG recreates the VM. For more information about preserving the state of MIG instances, see stateful MIGs.
Limitations
If you create instances with specific names:
- You must turn off autoscaling during the instance creation process.
- You must set the MIG's update policy to be opportunistic.
- If you are updating a regional MIG:
- You must disable proactive instance redistribution.
- You can't select which zone to create the VM in.
- You can't use duplicate VM instance names within a project.
You can use the gcloud CLI or REST to add VMs with specific names to an existing MIG.
gcloud
Use the instance-groups managed create-instance
command.
gcloud compute instance-groups managed create-instance INSTANCE_GROUP_NAME \ --instance INSTANCE_NAME \ [--region REGION | --zone ZONE]
Replace the following:
- INSTANCE_GROUP_NAME is the name of the regional or zonal MIG to add a new instance to.
- INSTANCE_NAME is the name you want to assign to the new instance.
REST
Send a POST request to the
regionInstanceGroupManagers.createInstances
method. For a zonal managed instance group, use the
instanceGroupManagers.createInstances
method. In the request body, include the instances
field with names for
one or more instances.
POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/instanceGroupManagers/INSTANCE_GROUP_NAME/createInstances { "instances": [ { "name": "INSTANCE_NAME_1" }, { "name": "INSTANCE_NAME_2" } ] }
Deleting specific instances from a group
You can delete individual VM instances in a managed instance group. Deleting
instances reduces the specified targetSize
of the instance group and removes
the VMs from any
target pools of which they
are a member.
Deleting specific instances from a managed instance group doesn't change any specified autoscaler settings. If you delete instances from a managed instance group, the autoscaler might detect an increase in the workload on the other instances in the group and increase the group size back to its previous level. To prevent this, stop the autoscaler before attempting to delete the instances.
If the group is part of a backend service that has enabled connection draining, it can take up to an additional 60 seconds after the connection draining duration has elapsed before the VM instance is removed or deleted.
Console
In the Google Cloud console, go to the Instance groups page.
Under the Name column of the list, click the name of the instance group where you want to delete individual instances. A page opens with the instance group properties and a list of instances that are included in the group.
In the Members section, from the list of instances select one or more instances that you want to delete.
Click Delete instance. The selected instances are deleted.
gcloud
To delete an instance with the gcloud CLI, use the
instance-groups managed delete-instances
command.
gcloud compute instance-groups managed delete-instances INSTANCE_GROUP_NAME \ --instances INSTANCE_NAME_1,INSTANCE_NAME_2 \ [--region REGION | --zone ZONE]
The command returns the operation status per instance:
SUCCESS
is returned if the gcloud CLI deleted the instance.FAIL
is returned for all instances if any instance that you specify in the request is not a member of the group, if any member is already being deleted or abandoned, or if the request fails for any other reason.SKIPPED
is returned only if you use the--skip-instances-on-validation-error
flag and the instance is not a member of the group or is already being deleted or abandoned.MEMBER_NOT_FOUND
is returned only for regional groups when the gcloud CLI wasn't able to resolve the zone from the instance name.
If you anticipate that your deletion request might conflict with concurrent
operations, use the --skip-instances-on-validation-error
flag. This flag
specifies whether the request should proceed even if the request includes
instances that are not members of the group or that are already being
deleted or abandoned—for example, instances that are being deleted by an
autoscaler. By default, if you omit this flag and such an instance
is specified in the request, the operation fails. The operation always fails
if the request contains a badly formatted instance name or a reference to
an instance that exists in a zone or region other than the group's zone or
region.
For example, the following command requests deletion of four instances, but three of them are no longer in the group:
gcloud compute instance-groups managed delete-instances example-mig \ --instances=example-instance-1,example-instance-2,example-instance-3,example-instance-4 \ --region=us-central1 \ --skip-instances-on-validation-error
In this example, three instances didn't pass validation, so they were
skipped, while example-instance-3
was deleted:
Updated [https://www.googleapis.com/compute/v1/projects/example-project/regions/us-central1/instanceGroupManagers/example-mig]. PROJECT ZONE INSTANCE STATUS VALIDATION_ERROR example-project us-central1-a example-instance-1 SKIPPED Cannot delete instance https://www.googleapis.com/compute/v1/projects/example-project/zones/us-central1-a/instances/example-instance-1 that was already deleted. example-project us-central1-a example-instance-2 SKIPPED Cannot delete instance https://www.googleapis.com/compute/v1/projects/example-project/zones/us-central1-a/instances/example-instance-2 that was already abandoned. example-project us-central1-a example-instance-3 SUCCESS example-project us-central1-a example-instance-4 SKIPPED Cannot find instance https://www.googleapis.com/compute/v1/projects/example-project/zones/us-central1-a/instances/example-instance-4.
If you omit the --skip-instances-on-validation-error
flag and if any
instance does not pass validation, then no instance is deleted:
gcloud compute instance-groups managed delete-instances example-mig \
--instances=example-instance-1,example-instance-2,example-instance-3,example-instance-4 \
--region=us-central1
Updated [https://www.googleapis.com/compute/v1/projects/example-project/regions/us-central1/instanceGroupManagers/example-mig].
PROJECT ZONE INSTANCE STATUS
example-project us-central1-a example-instance-1 FAIL
example-project us-central1-a example-instance-2 FAIL
example-project us-central1-a example-instance-3 FAIL
example-project us-central1-a example-instance-4 FAIL
REST
Send a POST request to the
regionInstanceGroupManagers.deleteInstances
method. For a zonal managed instance group, use the
instanceGroupManagers.deleteInstances
method.
POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/instanceGroupManagers/INSTANCE_GROUP_NAME/deleteInstances { "instances": [ "zones/ZONE/instances/INSTANCE_NAME_1", "zones/ZONE/instances/INSTANCE_NAME_2" ] }
If you anticipate that your deletion request might conflict with concurrent
operations, use the skipInstancesOnValidationError
field. This field
specifies whether the request should proceed even if the request includes
instances that are not members of the group or that are already being
deleted or abandoned—for example, instances that are being deleted by an
autoscaler. By default, if you omit this flag and such an instance
is specified in the request, the operation fails. The operation always fails
if the request contains a badly formatted instance name or a reference to
an instance that exists in a zone or region other than the group's zone or
region.
For example, the following request to delete 2 instances will succeed even if one of the instances is already deleted or being deleted:
POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/instanceGroupManagers/INSTANCE_GROUP_NAME/deleteInstances { "instances": [ "zones/ZONE/instances/INSTANCE_NAME_1", "zones/ZONE/instances/INSTANCE_NAME_2" ], "skipInstancesOnValidationError": true }
You can view instances that were skipped in the operation by viewing the
operation. For regional MIGs, use the
regionOperations.get
method.
For zonal MIGs, use the
zoneOperations.get
method.
Warnings are listed in the operation's warning field.
After you make a request to delete instances in a managed instance group, the instances stop as soon as the system can delete them. This process can take a significant amount of time depending on the number of instances that you delete from the group. Verify the status of the group or verify the status of the managed instances.
Abandoning instances from a MIG
You can separate a VM instance from a managed instance group to more easily debug issues with individual instances without affecting the group as a whole. Abandoning an instance from a group also removes the instance from load balancers that were assigned to the managed instance group. Target pools that were manually assigned to specific individual instances are not removed.
You cannot add an abandoned VM instance back to the group.
Abandoning instances reduces the specified targetSize
of the instance group,
but doesn't change any specified autoscaler settings. Managed instance groups
with an autoscaler continue to add or remove instances automatically as
necessary. For a regional MIG with autoscaling set to ONLY_SCALE_OUT
mode,
if you abandon a VM instance to reduce the MIG target size to the
autoscaler's recommended size, then
the autoscaler might create a new VM instance in the same zone of the abandoned
VM. In such cases, to avoid creation of a new VM instance, try abandoning VM
instance from a different zone.
If the group is part of a backend service that has enabled connection draining, it can take up to an additional 60 seconds after the connection draining duration has elapsed before the VM instance is removed or deleted.
Console
In the Google Cloud console, go to the Instance groups page .
Under the Name column of the list, click the name of the instance group from which you want to remove instances. A page opens with the instance group properties and a list of instances that are included in the group.
In the Members section, from the list of instances select one or more instances that you want to remove from the group.
Click Remove from group. The selected instances leave the group, but continue to run outside of the group.
gcloud
To remove an instance from the instance group
without deleting the VM, use the
instance-groups managed abandon-instances
command.
gcloud compute instance-groups managed abandon-instances INSTANCE_GROUP_NAME \ --instances INSTANCE_NAME_1,INSTANCE_NAME_2 \ [--region REGION | --zone ZONE]
REST
Send a POST request to the
regionInstanceGroupManagers.abandonInstances
method. For a zonal managed instance group, use the
instanceGroupManagers.abandonInstances
method.
POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/instanceGroupManagers/INSTANCE_GROUP_NAME/abandonInstances { "instances": [ "zones/ZONE/instances/INSTANCE_NAME_1", "zones/ZONE/instances/INSTANCE_NAME_2" ] }
After you make a request to abandon instances from a managed instance group, the group removes the instances as soon as possible. Verify the status of the group or verify the status of the managed instances.
Increase the group's size limit
By default, the size limit for a zonal MIG is 1,000 VMs, and the size limit for a regional MIG is 2,000 VMs. You can further increase these limits to 2,000 VMs for a zonal MIG and 4,000 VMs for a regional MIG.
To increase the limits, set the group's listManagedInstancesResults
field to
PAGINATED
. If you still need more VMs in the group, create multiple MIGs or
contact support.
Console
In the Google Cloud console, go to the Instance groups page.
Under the Name column of the list, click the name of the instance group of which you want to increase the size limit.
Click Edit to modify the instance group.
Expand the advanced settings section by clicking Show Advanced Configuration.
Under Managed instance list API call results, select the Paginated option.
Click Save to apply the changes.
gcloud
For an existing MIG, use the
update
command:
gcloud compute instance-groups managed update INSTANCE_GROUP_NAME \ --list-managed-instances-results=PAGINATED
For a new MIG, use the create
command:
gcloud compute instance-groups managed create INSTANCE_GROUP_NAME \ --template INSTANCE_TEMPLATE \ --size SIZE \ --list-managed-instances-results=PAGINATED
Terraform
To increase a MIG's size limit, set the list_managed_instances_results
argument to PAGINATED
.
The following sample increases the size limit of a
zonal MIG. For more information about the resource used in the sample, see
the google_compute_instance_group_manager
resource.
For a regional MIG, use the google_compute_region_instance_group_manager
resource.
To learn how to apply or remove a Terraform configuration, see Basic Terraform commands.
REST
For an existing zonal MIG, use the
instanceGroupManagers.patch
method
or, for a regional MIG, use the
regionInstanceGroupManagers.patch
method–for
example:
PATCH https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/region/REGION/regionInstanceGroupManagers/INSTANCE_GROUP_NAME { "listManagedInstancesResults": "PAGINATED", }
For a new zonal MIG, use the
instanceGroupManagers.insert
method
or, for a regional MIG, use the
regionInstanceGroupManagers.insert
method.
If you want to switch back to pageless list results, you must also revert
to the group's default size limit. To switch back, first ensure that the
group does not exceed its default size limit, then set the
listManagedInstancesResults
field to PAGELESS
.
What's next
- Learn about working with managed instances, for example, to delete, abandon, and recreate managed instances.
- View info about managed instance groups and managed instances.
- Troubleshoot managed instance groups.