# Cluster resource
<a name="cfn-cluster-resource"></a>

The CloudFormation cluster resource is formatted as shown in the following CloudFormation template snippet:

```
PclusterCluster:
  Type: Custom::PclusterCluster
  Properties:
    ServiceToken: !GetAtt [ PclusterClusterProvider , Outputs.ServiceToken ]
    ClusterName: !Sub 'c-${AWS::StackName}' # Must be different from StackName
    ClusterConfiguration:
    # Your Cluster Configuration
```

**Properties: **    
**ServiceToken: **  
The AWS ParallelCluster provider stack `ServiceToken` output.  
**ClusterName: **  
The name of the cluster to be created and managed. The name must not match the CloudFormation stack’s name. The name can't be changed after the cluster has been created.  
**ClusterConfiguration: **  
The cluster configuration YAML file, as described in [Cluster configuration file](cluster-configuration-file-v3.md). However, you can use the usual CloudFormation constructs, such as [Intrinsic functions](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference.html).  
**DeletionPolicy: **  
Defines whether to delete the cluster when the root stack is deleted. The default is `Delete`.    
**Retain: **  
Retain the cluster if the custom resource is deleted.  
To keep the retained cluster functioning, cluster-dependent resources, such as storage and networking, must have a deletion policy set to retain.  
**Delete: **  
Delete the cluster if the custom resource is deleted.

**`Fn::GetAtt` return values: **  
The `Fn::GetAtt` intrinsic function returns a value for a specified attribute of a type. For more information about using the `Fn::GetAtt intrinsic` function, see [Fn::GetAtt](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-getatt.html).    
**ClusterProperties: **  
The values from the [`pcluster describe-cluster`](pcluster.describe-cluster-v3.md) operation.  
**validationMessages: **  
A string containing all the validation messages that occurred during the last create or update operation.  
**logGroupName: **  
The name of the log group that's used for logging Lambda cluster operations. The log events are retained for 90 days and the log group is retained after cluster deletion.

**Example: **`Fn::GetAtt`:

```
# Provide the public IP address of the head node as an output of a stack
Outputs:
  HeadNodeIp:
    Description: The public IP address of the head node
    Value: !GetAtt [ PclusterCluster, headNode.publicIpAddress ]
```

**Example: **Simple, complete CloudFormation template with an AWS ParallelCluster custom resource:

```
AWSTemplateFormatVersion: '2010-09-09'
Description: >
 AWS ParallelCluster CloudFormation Template

Parameters:
  HeadNodeSubnet:
    Description: Subnet where the HeadNode will run
    Type: AWS::EC2::Subnet::Id

  ComputeSubnet:
    Description: Subnet where the Compute Nodes will run
    Type: AWS::EC2::Subnet::Id

  KeyName:
    Description: KeyPair to login to the head node
    Type: AWS::EC2::KeyPair::KeyName

Resources:
  PclusterClusterProvider:
    Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL: !Sub
        - https://${AWS::Region}-aws-parallelcluster.s3.${AWS::Region}.${AWS::URLSuffix}/parallelcluster/${Version}/templates/custom_resource/cluster.yaml
        - { Version: 3.15.0 }

  PclusterCluster:
    Type: Custom::PclusterCluster
    Properties:
      ServiceToken: !GetAtt [ PclusterClusterProvider , Outputs.ServiceToken ]
      ClusterName: !Sub 'c-${AWS::StackName}'
      ClusterConfiguration:
        Image:
          Os: alinux2
        HeadNode:
          InstanceType: t2.medium
          Networking:
            SubnetId: !Ref HeadNodeSubnet
          Ssh:
            KeyName: !Ref KeyName
        Scheduling:
          Scheduler: slurm
          SlurmQueues:
          - Name: queue0
            ComputeResources:
            - Name: queue0-cr0
              InstanceType: t2.micro
            Networking:
              SubnetIds:
              - !Ref ComputeSubnet

Outputs:
  HeadNodeIp:
    Description: The Public IP address of the HeadNode
    Value: !GetAtt [ PclusterCluster, headNode.publicIpAddress ]
  ValidationMessages:
    Description: Any warnings from cluster create or update operations.
    Value: !GetAtt PclusterCluster.validationMessages
```

To learn more about how to use the CloudFormation AWS ParallelCluster custom resource, see [Creating a cluster with CloudFormation](tutorials_09_cfn-custom-resource-v3.md).