CODEWITHSUNDEEP
aws-cloudformation
Evgeny Zislis
Evgeny Zislis

Reputation: 6957

How to specify dependencies in Custom CloudFormation resources?

When creating a Custom CloudFormation Resource implementation, the created resource can later be used to "add" more dependant children onto itself.

For example:

ResourceA:
  Type: Custom::Parent

ResourceB:
  Type: Custom::Child
  Properties:
    Parent: !Ref ResourceA

Is it sufficient to just add DependsOn to ResourceB to make sure that it gets removed before ResourceA receives the Delete request? Like so -

ResourceB:
  DependsOn: ResourceA
  Type: Custom::Child
  Properties:
    Parent: !Ref ResourceA

Or will there be a case where ResourceA receives a Delete request and fails, before ResourceB finished its process of removal?

Upvotes: 0

Views: 215

Answers (1)

Paulo Schreiner
Paulo Schreiner

Reputation: 1046

In this case you don't even need the DependsOn. Since you have a reference to A in the properties of B, cloudformation knows that B has a dependency on A, and will only start creating B when A is created. For deleting, the reverse happens: first B will be removed, then A. Cloudformation only deletes resources when no other resource depends on it.

Upvotes: 1

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