How to reuse existing resources in CloudFormation

amazon s3amazon-cloudformationamazon-web-services

I have an S3 bucket as a resource in my CloudFormation template, with DeletionPolicy set to Retain. This works as expected: when deleting the stack, it does indeed retain the bucket. However, when I attempt to create the stack again, creation fails while attempting to create the same bucket again, with an error message complaining that it already exists.

What do I need to add to my CloudFormation template to make it not try recreating a resource which already exist?

Relevant fragment of my template is as follows:

      "Resources": {
        "SomeS3Bucket" : {
          "Type" : "AWS::S3::Bucket",
          "DeletionPolicy" : "Retain",
          "Properties": {
              "BucketName": "SomeS3Bucket"
              }
          }

Best Answer

One approach is to add an input parameter to the CloudFormation template to indicate that an existing bucket should be used.

Use Condition clauses in the template to create the bucket only if the parameter indicates it is needed.

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