Creating an instance group with a Container Optimized Image

To run multiple instances of the service in Docker containers, you can create an instance group from a Container Optimized Image. In such groups, you can update Docker containers with VM metadata using the COI or Docker Compose specification.

Alert

When creating instance groups, keep the limits in mind. Not to disrupt the component Instance Groups, do not update or delete manually created resources: target group Network Load Balancer, VMs, and disks. To do this, change or delete the entire group.

By default, all operations in Instance Groups are performed on behalf of a service account. If you don't have a service account, create one.

To create an instance group built on a Container Optimized Image:

If you don't have the Yandex.Cloud command line interface yet, install and initialize it.
The folder specified in the CLI profile is used by default. You can specify a different folder using the --folder-name or --folder-id parameter.
View a description of the create instance group command in the CLI:
```
$ yc compute instance-group create --help
```
Check whether there are networks in the folder:
```
$ yc vpc network list
```
If there aren't any, create one.
Create a YAML file with a name like specification.yaml.
Select the latest version of the Container Optimized Image from the public images.

To get the ID of the latest version of the Container Optimized Image image, run the command:
```
$ yc compute image get-latest-from-family container-optimized-image --folder-id standard-images
id: <image ID>
folder_id: standard-images
...
```

In the specification.yaml file you created, specify the following:

General information about the group:

name: container-optimized-group
service_account_id: aje3932acd8avp6edhbt
description: "This instance group was created from YAML config."

Keys:

Key	Value
`name`	A name for the instance group. The name must be unique within the folder. The name may contain lowercase Latin letters, numbers, and hyphens. The first character must be a letter. The last character can't be a hyphen. The maximum length of the name is 63 characters.
`service_account_id`	ID of the service account.
`description`	A description of the instance group.

Instance template:

instance_template:
    platform_id: standard-v1
    resources_spec:
        memory: 2G
        cores: 2
    boot_disk_spec:
        mode: READ_WRITE
        disk_spec:
            image_id: fd81a49qficqvt0dthu8
            type_id: network-hdd
            size: 32G
    network_interface_specs:
        - network_id: c64mknqgnd8avp6edhbt
          primary_v4_address_spec: {}
    metadata:
        docker-container-declaration: |-
            spec:
                containers:
                    - name: nginx
                      image: cr.yandex/mirror/nginx:1.17.4-alpine
                      securityContext:
                        privileged: false
                      tty: false
                      stdin: false

The disk size is specified in bytes by default. You can specify a different unit of measurement using the applicable suffix.

Name	Example of a YAML file entry:
Kilobyte	1073741824k
Megabyte	1048576m
Gigabyte	1024g
Terabyte	1t

Keys:

Key	Value
`platform_id`	Platform ID.
`memory`	Amount of memory (RAM).
`cores`	Number of processor cores (vCPUs).
`mode`	Disk access mode. - `READ_ONLY`: read-only access. - `READ_WRITE`: read/write access.
`image_id`	ID of the public Container Optimized Image.
`type_id`	Disk type.
`size`	Disk size.
`network_id`	The `default-net` ID.
`primary_v4_address_spec`	IPv4 specification. Only IPv4 is currently available. You can allow public access to group instances by specifying the IP version for the public IP address. For more information, see Template description in a YAML file.
`metadata`	Values to pass to the VM metadata.
`docker-container-declaration`	The key in the VM metadata that is used with the COI specification of the Docker container. In the metadata, you can use the Docker Compose specification. To do this, specify the `docker-compose` key instead of the `docker-container-declaration` key.

Policies:

deploy_policy:
    max_unavailable: 1
    max_expansion: 0
scale_policy:
    fixed_scale:
        size: 3
allocation_policy:
    zones:
        - zone_id: ru-central1-a

Keys:

Key	Value
`deploy_policy`	Deployment policy for instances in the group.
`scale_policy`	Scaling policy for instances in the group.
`allocation_policy`	Policy for allocating instances across zones and regions.

Full code for the specification.yaml file:

name: container-optimized-group
service_account_id: aje3932acd8avp6edhbt
description: "This instance group was created from YAML config."
instance_template:
    service_account_id: aje3932acd8avp6edhbt # ID of the service account to access private Docker images.
    platform_id: standard-v1
    resources_spec:
        memory: 2G
        cores: 2
    boot_disk_spec:
        mode: READ_WRITE
        disk_spec:
            image_id: fd81a49qficqvt0dthu8
            type_id: network-hdd
            size: 32G
    network_interface_specs:
        - network_id: c64mknqgnd8avp6edhbt
          primary_v4_address_spec: {}
    metadata:
        docker-container-declaration: |-
            spec:
                containers:
                    - name: nginx
                      image: cr.yandex/mirror/nginx:1.17.4-alpine
                      securityContext:
                        privileged: false
                      tty: false
                      stdin: false
deploy_policy:
    max_unavailable: 1
    max_expansion: 0
scale_policy:
    fixed_scale:
        size: 3
allocation_policy:
    zones:
        - zone_id: ru-central1-a

Note

To use in specification.yaml the Docker Compose specification, specify the docker-compose key instead of the docker-container-declaration key.

Create an instance group in the default folder:
```
$ yc compute instance-group create --file specification.yaml
```
This command creates a group of three similar instances with the following characteristics:
- Named container-optimized-group.
- From the latest version of the public Container Optimized Image.
- With a running Docker container based on cr.yandex/mirror/nginx:1.17.4-alpine.
- In the default-net network.
- In the ru-central1-a availability zone.
- With 2 vCPUs and 2 GB of RAM.
- With a 32 GB network HDD.