What is the AWS Attribute outputs and ImportValue in cloudformation

Question

i'm starting my AWS journey and today got a chance to Create cloudformation stack for creating a filesystem on the AWS, i was able to spun the filesystem, however I have few doubts about some values and functions/attributes as those were given by someone in the team and he on long vacations so, asking here for help.

Below is cloudfoemation Stack which works Just fine.

Cloudformaton Stack:

---
Description: "Create FSxN filesystem"
Resources:
  MytestCluster:
    Type: "AWS::FSx::FileSystem"
    Properties:
      FileSystemType: "ONTAP"
      StorageCapacity: "1024"
      SubnetIds: ['subnet-0f349h6eee098b0pg']
      OntapConfiguration:
        DeploymentType: "SINGLE_AZ_1"
        PreferredSubnetId: "subnet-0f349h6eee098b0pg"
        ThroughputCapacity: "128"
        FsxAdminPassword: '{{resolve:secretsmanager:fsx_admin_password}}'
      SecurityGroupIds:
        - !ImportValue 'KPCL-FSxforONTAPsgID'
      Tags:
        - Key: "Backup"
          Value: "None"
  MytestSVM:
    Type: "AWS::FSx::StorageVirtualMachine"
    Metadata:
      cfn-lint:
        config:
          ignore_checks:
            - E3001
    Properties:
      FileSystemId: !Ref MytestCluster
      Name: svmdemo
      RootVolumeSecurityStyle: "UNIX"
      SvmAdminPassword: '{{resolve:secretsmanager:svm_admin_password}}'
      Tags:
        - Key: "Backup"
          Value: "None"
  fsxndemovolume:
    Type: "AWS::FSx::Volume"
    Metadata:
      cfn-lint:
        config:
          ignore_checks:
            - E3001
    Properties:
      Name: myTestVol001
      OntapConfiguration:
        JunctionPath: /myVolume001
        SizeInMegabytes: 1536000
        StorageEfficiencyEnabled: true
        StorageVirtualMachineId: !Ref MytestSVM
      VolumeType: "ONTAP"
      Tags:
        - Key: "Backup"
          Value: "None"
Outputs:
  FileSystemId:
    Value: !Ref "MytestCluster"
  SvmId:
    Value: !Ref "MytestSVM"
...

I would like Understand:

I have few doubts to myself to clear which i tried to understand from document but couldn't comprehend well, hence though taking expert suggestion..

First one: below under SecurityGroupIds what does - !ImportValue mean here.

  SecurityGroupIds:
    - !ImportValue 'KPCL-FSxforONTAPsgID'

Second one: What is outputs means here.

Outputs:
  FileSystemId:
    Value: !Ref "MytestCluster"
  SvmId:
    Value: !Ref "MytestSVM"

Last one: what is ignore_checks: and its value - E3001 here.

      ignore_checks:
        - E3001

Please help me to understand.

score 1 · Answer 1 · answered Jul 28 '22 at 19:44

1

Outputs in stack creates exports in cloudformation which can be listed in AWS Console, !Import directive is used to reference to export from another stack.

cfn-lint section in metadata is used to silent errors in CloudFormation Linter tool and has no impact to the resource itself.

answered Jul 28 '22 at 19:44

Lasek

290
1
3

There is no such thing as `!Import`. – Marcin Jul 29 '22 at 00:29
@Marcin, Its `!ImportValue` – micron cloud Jul 29 '22 at 01:57
@Marcin, Would you mind explaining please, we'll also learn something from you. – micron cloud Jul 29 '22 at 01:59
@Lasek, thanks for the answer +1 for the, will mark that answer in another few mins. – micron cloud Jul 29 '22 at 02:02

score 1 · Accepted Answer · answered Jul 29 '22 at 02:11

First one: below under SecurityGroupIds what does - !ImportValue mean here.

The following:

      SecurityGroupIds:
        - !ImportValue 'KPCL-FSxforONTAPsgID'

means that in the current stack your are going to import security group ID which was exported by some other stack.

This export/import functionality allows you to decouple and reuse your infrastructure. Instead of having everything in one stack, you can make one stack with network resources (its a common setup), such as security groups, subnets, VPCs, and other stacks that actual use those resources.

Second one: What is outputs means here.

Outputs allow you to return values from your stacks. You can think of them as a type of return values from functions in common programming languages.

Output values have lots of use-cases. Examples are: they can be exported, and imported in other stacks. They can also be queried programmatically, in case your stacks are part of some CI/CD pipelines or other application. They can be used as input parameters to other stacks, again as port of some CI/CD pipeline. This is alternative to export/import functionality.

Last one: what is ignore_checks: and its value - E3001 here.

This is some extra code not related to CloudFormation itself. It is actually a hint to Visual Studio Code cfn-lint-visual-studio-code editor to ignore some auto checks it does.

Marcin, Thanks for detailed explanation +1, i'll go through it ., I believe we can remove that CFN lint part from teh CFN as that's not play any role here. — micron cloud, Jul 29 '22 at 02:15

What is the AWS Attribute outputs and ImportValue in cloudformation

2 Answers2