Cross Stack References

[skorfmann]

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Description

With #636 we've introduced multiple stacks. We should enable referencing resources across stacks.

References

• Blocked on Token System #525

[kwalsh-tr]

Does anyone know of a temporary alternative method of passing references between stacks?

[DanielMSchmidt]

I think the nicest solution currently would be using DataSources to get a reference to an object into another stack. For this you need to have the name and type of the element you want to transfer. The name can be a global constant so that it can be used by the resource and data source.

const clusterName = "my-cluster"
class InfrastructureLayer extends TerraformStack {  
  constructor(scope: Construct, name: string) {    
    super(scope, name);

    new GKECluster(this, "doesNotMatter", {
      name: clusterName,
      // ...
    })
  }
}

class ApplicationLayer extends TerraformStack {  
  constructor(scope: Construct, name: string) {    
    super(scope, name);

    // This will fail if the cluster does not exist already
    new DataGKECluster(this, "doesNotMatter", {
      name: clusterName,
      // ...
    })
  }
}

const app = new App();
new InfrastructureLayer(app, "infrastructure");
new ApplicationLayer(app, "development");

[ansgarm]

Another option is to write the value you want to refer to into an output and read that value from a remote state in the other stack.
Edit: also described in the guide.

[ZacharyATanenbaum]

I think the nicest solution currently would be using DataSources to get a reference to an object into another stack. For this you need to have the name and type of the element you want to transfer. The name can be a global constant so that it can be used by the resource and data source.

Is this work-around supported within Python? I'm getting the following error when attempting to use a "Data Source" for a Python Lambda Layer Version.

ImportError: cannot import name 'DataLambdaLayerVersion' from 'imports.aws'

[jsteinich]

Is this work-around supported within Python? I'm getting the following error when attempting to use a "Data Source" for a Python Lambda Layer Version.

ImportError: cannot import name 'DataLambdaLayerVersion' from 'imports.aws'

You want DataAwsLambdaLayerVersion. Data source names are currently a bit more verbose than resource names.

[DanielMSchmidt]

Here is a POC around this topic I did, for those interested: #1179

[phinze]

From discussion, this can be broken down into two separate issues:

1. Getting cross-stack references working in code - this issue can continue to track that part
2. Determining and implementing the CLI workflows associated with cross-stack references - this is captured at a high level with Deploy Multiple Stacks at Once  #650

We plan to tackle this part first, then we'll circle around to the CLI workflows once the core functionality is in place.

[github-actions]

I'm going to lock this issue because it has been closed for 30 days. This helps our maintainers find and focus on the active issues. If you've found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.