Resolver of a parameter that is the output of another stack

[sergioissi]

Hi, is it possible to give as input paramter to a resolver a parameter that is an output of another stack?
This is the example:

template_path: templates/roberto.yaml
parameters:
  Project: roberto
  Repository: !stack_output pipeline/ecr::Repository
  Tag: !get_tag !stack_output pipeline/ecr::Repository

This is the error:
yaml.parser.ParserError: while parsing a block mapping
in "", line 3, column 3:
Project: roberto
^
expected , but found ''
in "", line 16, column 20:
Tag: !get_tag !stack_output pipeline/ecr::Repository

Trying like this:

template_path: templates/roberto.yaml
parameters:
  Project: roberto
  Repository: !stack_output pipeline/ecr::Repository
  Tag: !get_tag !Repository

This is the error:
Invalid parameter at 'repositoryName' failed to satisfy constraint: 'must satisfy regular expression '(?:[a-z0-9]+(?:[.-][a-z0-9]+)/)[a-z0-9]+(?:[.-][a-z0-9]+)*''

[nabeelamjad]

You should be able to use !stack_output_external, let me know if something like this works:

template_path: templates/roberto.yaml

parameters:
  ...
  Roberto: !stack_output_external pipeline/ecr::Repository

[JuanCanham]

Not at this time, somebody looked at this a while ago, but it never got merged, your '!get_tag' resolve could do chain the resolvers, but it would be messy.

I'll see if I can produce a hook for this to unblock you (today/tomorrow), but as the hooks system is being overhalled in 2.0, not sure the original PR will be accepted

[njsnx]

Hi @sergioissi - First of all, make sure your outputs your Parameters are actually set to outputs, you can do this using describe-outputs command.

Can you clarify what you are expecting to get here.
From what I can tell, you want the Output from Stack B to be used as the value for a Parameter in stack A. If both stacks are built in the same Sceptre configuration, you can use !stack_output like so:

parameters:
  VpcId: !stack_output vpc::VpcId```

From the error you are providing here, if this *is* what you are trying to achieve, your error message seems un-related.

Let me know if you have further information or if I am way off :)

[njsnx]

@sergioissi After another go at reading your question versus examples, my new understanding is this.

You have created a new resolver called get_tag which you want to use the returned value of for the Tag parameter. In your example, you want to pass the returned value of the !stack_output resolver as the input into this new resolver - as @JuanCanham suggests, nested resolver usage doesn't currently work.

In the mean time, my suggestion would be to look at the use of variables and variable-files. This would allow you to set a tag value in that variable file and use the value of that variable where needed on both stacks.

[JuanCanham]

I put something together, that should work on sceptre v1 and sceptre v2, unfortunately the sceptre v1 part is a little hacky as we didn't support extensibility through module entry_points, so i'm not sure @jakubincloud will let me open source it under the cloudreach org, however i'm happy to share it with anybody that asks as the code should work, has tests, etc

https://github.com/cloudreach/sceptre_combine_resolvers

[sopeters]

+1