ec2: how to specify 'MetaData' for the instance?

[sonaliks]

Describe the feature

The "CfnInstance" Construct documentation[1] does not define how to specify 'MetaData' for the instance. And the "addMetadata(key, value)" construct can have only key-pair values while the instance metadata has to be quite large.

The solution that worked is using "addOverride" function:

As per Link[2] you can make use of "addOverride" function to add metadata to a 'CfnInstance' construct. An example[3] is as follows:

---

asgLaunchConfig.addOverride("Metadata", {
"AWS::CloudFormation::Init": {
"FOO": "BAR",
}
});

However ask from Service team:

1. Kindly add a method in CDK "CfnInstance" construct to be able to add large metadata. this is apart from "addMetadata" method.
2. If the "addOverride" should be the only method then kindly update the documentation[1] and mention this as this is not properly documented and is a common usecase.

[1] https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_ec2.CfnInstance.html
[2] https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_ec2.CfnInstance.html#addwbrmetadatakey-value
[3] #5087
[4] #777

Use Case

NA

Proposed Solution

NA

Other Information

NA

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

V2

Environment details (OS name and version, etc.)

MAC

[pahud]

What metadata are you trying to add for the ec2 instance? Is it instance metadata? If yes, I am afraid cloudformation does not allow you to add MetadataOptions to ec2 instance and this is tracking in cloudformation coverage roadmap here.

However, you may specify MetadataOptions in CfnLaunchConfiguration or in LauchTemplateDataProperty.

Is this something you are looking for?

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[sonaliks]

Thank you @pahud for your response. I understand that "cloudformation does not allow you to add MetadataOptions to ec2 instance" however i was able to add the metadata using "addOverride" function. Further "CfnInstance" is equivalent to "AWS::EC2::Instance" in CloudFormation. As per doc[1] the "AWS::EC2::Instance" Resource type does support CFN Metadata. I have tested same in Cloudformation and it works.

However in CDK "CfnInstance" resource "addMetadata(key, value)" construct can have only key-pair values while the instance metadata has to be quite large.

Hence asking for a native function for same in "CfnInstance" resource.

[pahud]

Please note the addMetadata() in the CfnInstance API reference is essentially to add CloudFormation Resource Metadata instead of EC2 instance metadata options. If you look at AWS::EC2::Instance there's no property that allows you to specify instance metadata options. If you really need to specify instance metadata options I believe you will need to specify that either in LauchConfiguration or LaunchTemplate as described above.

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