Replacement Warnings

Reading a Change Set's Replacement Warnings

Each entry in a change set is a ResourceChange with an Action (Add, Modify, Remove, Import, Dynamic); a Modify also has a Scope, Details giving each changed property's RequiresRecreation (Never, Conditionally or Always, as in the property's Update requires line), and a Replacement flag for the worst of them. False means an in-place update with the same physical ID; True means a new resource is created and the old one deleted, data and all; Conditional depends on values known only at deploy time, so treat it as True.

For the stage switch, TableName is a create-only property of AWS 24 ::DynamoDB 24 ::Table, so AWS reports "Replacement": "True" and a detail with "RequiresRecreation": "Always", and executing it creates booknest-prod-fn-books, repoints the stack and deletes the dev table with its data (not run here). LocalStack 4.13.1 63,725 computes something else:

LocalStack's view of the change, and what executing it didYAML

CS=$(aws cloudformation list-change-sets --stack-name booknest-fn \
  --query 'Summaries[0].ChangeSetId' --output text)
aws cloudformation describe-change-set --change-set-name "$CS" \
  --query 'Changes[].ResourceChange'
aws cloudformation execute-change-set --change-set-name "$CS"
aws cloudformation wait stack-update-complete --stack-name booknest-fn
aws cloudformation describe-stacks --stack-name booknest-fn --output text \
  --query 'Stacks[0].[StackStatus,Parameters[0].ParameterValue]'
aws dynamodb list-tables --output text

Output

[
    {
        "Action": "Modify",
        "LogicalResourceId": "BooksTable",
        "PhysicalResourceId": "booknest-dev-fn-books",
        "ResourceType": "AWS::DynamoDB::Table",
        "Replacement": "False"
    }
]
UPDATE_COMPLETE   prod
TABLENAMES   booknest-dev-fn-books

It called the change an in-place Modify with no details, and the update "completed" with Stage=prod while the table kept its dev name. On AWS, search every change set for "Replacement": "True" before executing, and give stateful resources an UpdateReplacePolicy (Deletion Policies); on LocalStack, check create-only properties yourself in the resource reference.

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