Creating groups of unmanaged instances

An unmanaged instance group is a collection of virtual machines (VMs) that reside in a single zone, VPC network, and subnet. An unmanaged instance groups is useful for grouping together VMs that require individual configuration settings or tuning.

For VMs that require consistent configuration settings, you can use a managed instance group (MIG) with an instance template. When possible, consider using managed instance groups instead of unmanaged ones. To create a managed instance group, see Creating groups of managed instances.

You can add either type of instance group as a backend to a Google Cloud load balancer. For more information, see Cloud Load Balancing overview. For the number of VMs per instance group that Cloud Load Balancing supports, see VMs per instance group.

To learn more about instance groups, see Instance groups overview.

Before you begin

If you want to use the command-line examples in this guide, do the following:
1. Install or update to the latest version of the gcloud command-line tool.
2. Set a default region and zone.
If you want to use the API examples in this guide, set up API access.
Read about the difference between managed and unmanaged instance groups.

Working with unmanaged instance groups

Creating groups

Unlike managed instance groups, unmanaged instance groups are just collections of distinct VMs that do not share a common instance template. You simply create a group, and add individual VMs to the group.

Console

In the Cloud Console, go to the Instance groups page.
Go to the Instance Groups page
Click Create instance group.
Click New unmanaged instance group.
Enter a name for the unmanaged instance group.
Under Location, select a region and a zone.
Select a Network and Subnetwork.
Under VM instances, select the VMs to add to this group.
Click Create.

gcloud

To create a new unmanaged instance group, use the instance-groups unmanaged create command:

gcloud compute instance-groups unmanaged create instance-group-name \
    --zone=zone

Replace the following:

instance-group-name: The name of the group you want to create.
zone: The zone where you want to create the group.

API

To create an unmanaged instance group with the API, send a POST request using the instanceGroups.insert method:

POST https://compute.googleapis.com/compute/v1/projects/project-id/zones/zone/instanceGroups

{
   "name": "instance-group-name"
}

Replace the following:

instance-group-name: The name of the group you want to create.
zone: The zone where you want to create the group.
project-id: The project ID for the project containing the group.

When you create a new unmanaged instance group with gcloud command-line tool or the API, no VMs are added to it automatically. You can add VMs to the unmanaged instance group manually.

Listing and describing groups

Retrieve a list of existing unmanaged instance groups.

Console

In the Cloud Console, the Instance groups page lists existing unmanaged and managed instance groups.

Go to the Instance Groups page

gcloud

To list all unmanaged instance groups in your project with the gcloud command-line tool, use instance-groups unmanaged list:

gcloud compute instance-groups unmanaged list

To see information about a specific unmanaged instance group, use the instance-groups unmanaged describe command:

gcloud compute instance-groups unmanaged describe instance-group-name \
   --zone=zone

Replace the following:

instance-group-name: The name of the group to describe.
zone: The zone of the group.

API

To list instance groups with the API, send a GET request using the instanceGroups.list method:

GET https://compute.googleapis.com/compute/v1/projects/project-id/zones/zone/instanceGroups

To obtain information about a specific unmanaged instance group with the API, send a GET request using the instanceGroups.get method:

GET https://compute.googleapis.com/compute/v1/projects/project-id/zones/zone/instanceGroups/instance-group-name

Replace the following:

instance-group-name: The name of the group to describe.
zone: The zone of the group.
project-id: The project ID for the project containing the group.

Deleting groups

Unlike a managed instance group, deleting an unmanaged instance group does not delete any of the VMs within the group. Deleting an unmanaged instance group only removes the logical grouping of VMs.

You can't delete an instance group if the group is a backend of a Google Cloud load balancer. You must first remove the backend from the backend service.

Console

In the Cloud Console, go to the Instance groups page.
Go to the Instance Groups page
Select one or more unmanaged instance groups from the list.
Click Delete to remove the groups. The groups are removed, but the VMs in the groups are not deleted.

gcloud

To delete an unmanaged instance group, use the instance-groups unmanaged delete command:

gcloud compute instance-groups unmanaged delete instance-group-name \
    --zone=zone

Replace the following:

instance-group-name: The name of the group you want to delete.
zone: The zone of the group.

API

To delete an unmanaged instance group with the API, send a DELETE request using the instanceGroups.delete method:

DELETE https://compute.googleapis.com/compute/v1/projects/project-id/zones/zone/instanceGroups/instance-group-name

Replace the following:

instance-group-name: The name of the group you want to delete.
zone: The zone of the group.
project-id: The project ID for the project containing the group.

Group membership

Adding VMs

After you create an unmanaged instance group, you can add VMs to the group.

Console

In the Cloud Console, go to the Instance groups page.
Go to the Instance Groups page
Under the Name column of the list, click the name of the instance group where you want to add your VMs. A page opens with the instance group properties and a list of VMs that are already part of the group.
Click Edit to modify this unmanaged instance group.
Under VM instances select one or more existing VMs to add to the group. You can only select VMs that are in the same zone, VPC network, and subnet as existing VMs.
Click Save to add the new VMs to the group.

gcloud

To add instances to an unmanaged instance group, use the instance-groups unmanaged add-instances command:

gcloud compute instance-groups unmanaged add-instances instance-group-name \
    --zone=zone \
    --instances=list-of-VM-names

Replace the following:

instance-group-name: The name of the group to which you want to add VMs.
zone: The zone of the group.
list-of-VM-names: A comma-delimited list of VMs in the same zone, VPC network, and subnet.

API

To add VMs to an unmanaged instance group with the API, send a POST request using the instanceGroups.addInstances method:

POST https://compute.googleapis.com/compute/v1/projects/project-id/zones/zone/instanceGroups/instance-group-name/addInstances

   {
      "instances": [
         {
         "instance": "https://www.googleapis.com/compute/v1/projects/project-id/zones/zone/instances/instance-1-name",
         "instance": "https://www.googleapis.com/compute/v1/projects/project-id/zones/zone/instances/instance-2-name",
         ....
         }
      ]
   }

Replace the following:

instance-group-name: The name of the group to which you want to add VMs.
zone: The zone of the group.
project-id: The project ID for the project containing the group.
instance-1-name and instance-2-name: These are names of the VMs, in the same zone, VPC network, and subnet, that you want to add to the group.

Listing VMs

You can retrieve a list of member VMs in an unmanaged instance group.

Console

In the Cloud Console, go to the Instance groups page.
Go to the Instance Groups page
Under the Name column of the list, click the name of the unmanaged instance group that you want to view. A page with the list of instances that are included in the group appears.

gcloud

To list the VMs in an unmanaged instance group, use the instance-groups unmanaged list-instances command:

gcloud compute instance-groups unmanaged list-instances instance-group-name \
   --zone=zone

Replace the following:

instance-group-name: The name of the group whose members you want to list.
zone: The zone of the group.

API

To list VMs in an unmanaged instance group with the API, send a POST request using the instanceGroups.listInstances method:

POST https://compute.googleapis.com/compute/v1/projects/project-id/zones/zone/instanceGroups/instance-group-name/listInstances

Replace the following:

instance-group-name: The name of the group whose members you want to list.
zone: The zone of the group.
project-id: The project ID for the project containing the group.

Removing VMs

You can remove VMs from an unmanaged instance group. Removing a VM from the instance group does not delete the VM.

Console

In the Cloud Console, go to the Instance groups page.
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 VMs. A page opens with the instance group properties and a list of VMs that are included in the group.
In the list, select one or more VMs that you want to remove from the group.
Click Remove from group. VMs that you remove from an unmanaged instance group continue to exist and run unless you stop or delete them.

gcloud

To remove VMs from an unmanaged instance group, use the instance-groups unmanaged remove-instances command:

gcloud compute instance-groups unmanaged remove-instances instance-group-name \
    --zone=zone \
    --instances=list-of-VM-names

Replace the following:

instance-group-name: The name of the group that contains instances to remove.
zone: The zone of the group.
list-of-VM-names: A comma-delimited list of VMs that you want to remove from the group.

API

To remove VMs from an unmanaged instance group with the API, send a POST request using the instanceGroups.removeInstances method. You can simultaneously remove multiple VMs as shown below:

POST https://compute.googleapis.com/compute/v1/projects/project-id/zones/zone/instanceGroups/instance-group-name/removeInstances
{
    "instances": [
        {
        "instance": "https://www.googleapis.com/compute/v1/projects/project-id/zones/zone/instances/instance-1-name",
        "instance": "https://www.googleapis.com/compute/v1/projects/project-id/zones/zone/instances/instance-2-name",
        ....
        }
    ]
}

Replace the following:

instance-group-name: The name of the group that contains instances to remove.
zone: The zone of the group.
project-id: The project ID for the project containing the group.
instance-1-name and instance-2-name: These are names of the VMs that you want to disassociate from the group.

Working with named ports

Named ports are key-value pairs that represent a port's name and number. The port name represents a name of a service or application. The port number represents the port that service or application runs on.

Named ports are used by Cloud Load Balancing. Load balancers that act as proxies subscribe to a single named port in their backend service configuration. The port's name is translated to a port number based on the named port's mapping of each instance group backend.

For example, a backend service can subscribe to a port that is named http-port. The backend instance group can have a port named http-port:80. The backend instance group instructs the load balancer to send traffic to a VM in the group on port 80 using a protocol (such as TCP). The protocol is defined in the load balancer's backend service.

Named ports are simple metadata used by proxy load balancers. Named ports do not control network or firewall resources in Compute Engine.

Multiple port numbers for a named port

You can assign multiple ports for each service name. You can also assign multiple service names for each port.

Keep in mind the following points:

Traffic is balanced between all ports with the same port name.
A given backend service can only forward traffic to one named port at a time.
If you use multiple port numbers for a named port, the ports must all be for the same application.

For example, http:80,http:8080 works, but http:80,http:443 doesn't work because port 80 generally doesn't support TLS.

You can assign multiple named ports in an instance group. To illustrate, consider an example backend service that subscribes to the named port http-port, and that has two backend instance groups:

instance-group-a with a named port of http-port:80
instance-group-b with a named port of http-port:79

This backend service sends traffic to port 80 for VMs in instance-group-a and port 79 for VMs in instance-group-b.

When you add the same instance group to multiple backend services (for multiple load balancers) and the instance group serves different ports on each load balancer, don't add all the port numbers to a single named port. Instead create a unique named port and map it to a set of ports that each backend service should serve.

For example, suppose you have three applications, each with its own load balancer. Each application has its own port number: 81 for app1, 82 for app2, and 83 for app3. Assuming that all three backend services are using a common instance group, assign the named ports for this instance group as [app1:81, app2:82, app3:83].

Named ports and health checks

For a named port with multiple port numbers on a backend service to work in an external HTTP(S) load balancer or internal HTTP(S) load balancer, the health check must have the --use-serving-port flag instead of a specific port number. This option is not available in the Google Cloud Console. You must use gcloud or the API to set --use-serving-port.

For example, suppose you have an application that load balances the traffic on three different ports (81, 82, 83) on the same backend service with a single instance group. You can assign the ports for this instance groups as [app:81, 82, 83]. The health check in this scenario must have the --use-serving-port flag.

For more information, see the load balancing health check documentation.

Named ports and firewall rules

Named ports do not create or modify Google Cloud firewall rules. To permit traffic to backend VMs, you must still create the necessary firewall rules.

Named ports and backend services

In addition to the instance group configuration, you must also configure the backend service. For example, suppose you set the named port on an instance group with the name my-service-name and the port 8888:

gcloud compute instance-groups set-named-ports my-unmanaged-ig \
    --named-ports=my-service-name:8888

Then you must refer to the named port in the backend service configuration with the --port-name on the backend service set to my-service-name:

gcloud compute backend-services update my-backend-service \
    --port-name=my-service-name

Creating named ports

Console

In the Cloud Console, go to the Instance groups page.
Go to Instance Groups
Under the Name column of the list, click the name of the instance group where you want to specify named ports. A page opens with the instance group properties.
Click Edit to modify this unmanaged instance group.
In the Port name mapping (Optional) section, click Add item, and enter a port name and its number. Add or remove other named ports as necessary.
Click Save to update the list of named ports for the unmanaged instance group.

gcloud

To add named ports to an unmanaged instance group, use the instance-groups unmanaged set-named-ports command:

gcloud compute instance-groups unmanaged set-named-ports instance-group-name \
    --zone=zone \
    --named-ports=port-name:port-number,...

To list named ports in an unmanaged instance group use the instance-groups unmanaged get-named-ports command:

Set one or more named ports using the set-named-ports command:

gcloud compute instance-groups unmanaged set-named-ports INSTANCE_GROUP \
      --named-ports PORT_NAME:PORT,PORT_NAME:PORT

For example:

gcloud compute instance-groups unmanaged set-named-ports INSTANCE_GROUP \
      --named-ports name1:80,name2:8080

To assign multiple ports to each service name or multiple names for each service, create more than one entry for each name or port. For example, if ports 10, 20, and 80 are for the same application, you can assign name1 to all of those ports. Additionally, you might assign two names, name2 and name3 to port 8080. Finally, you might assign port 9000 to name4, as in the following example:

gcloud compute instance-groups unmanaged set-named-ports INSTANCE_GROUP \
      --named-ports name1:10,name1:20,name1:80,\
                    name2:8080,name3:8080,\
                    name4:9000

To remove all named ports from an unmanaged instance group with the gcloud command-line tool, use instance-groups unmanaged set-named-ports with an empty list of named ports:

gcloud compute instance-groups unmanaged set-named-ports instance-group-name \
    --zone=zone \
    --named-ports=""

In all the examples above, replace the following if present:

instance-group-name: The name of the instance group.
zone: The zone of the group.
port-name and port-number: The port name and number represent a mapping from a name you choose to a port number. You can specify multiple mappings separated by commas; for example, port-one:80,port-two:8080 is a valid list of named ports.

API

Describe the instance group and note the fingerprint.
To add named ports with the API, send a POST request using the instanceGroups.setNamedPorts method. If you want to remove all named ports, set namedPorts to an empty list.
```
POST https://compute.googleapis.com/compute/v1/projects/project-id/zones/zone/instanceGroups/instance-group-name/setNamedPorts

{
    "fingerprint": "fingerprint",
    "namedPorts": [
        {
        "name": "port-name",
        "port": port-number
        },
        {
        "name": "port-name",
        "port": port-number
        },
        ....
    ]
}
```
Replace the following:
- instance-group-name: The name of the instance group.
- zone: The zone of the group.
- project-id: The project ID for the project containing the group.
- port-name and port-number: The port name and number represent a mapping from a name you choose to a port number.
- fingerprint: This is the fingerprint from the previous step.

What's next

Create a zonal managed instance group.
Create a regional managed instance group.
Learn about Cloud Load Balancing.