feat: import existing table to amplify managed table

[dpilch]

Description of changes

Add a feature to import existing DynamoDB tables to an Amplify managed table. Import validation will come with a later PR.

CDK / CloudFormation Parameters Changed

• New data source strategy: IMPORTED_AMPLIFY_TABLE.
• New construct prop: importedAmplifyDynamoDBTableMap.
• Final naming on these can be updated before merging to main.

importedAmplifyDynamoDBTableMap will define a mapping of model name to imported table name. All models defined with the IMPORTED_AMPLIFY_TABLE should have a matching key in the importedAmplifyDynamoDBTableMap prop.

import * as cdk from "aws-cdk-lib";
import { Construct } from "constructs";
import {
  AmplifyGraphqlApi,
  AmplifyGraphqlDefinition,
} from "@aws-amplify/graphql-api-construct";
import * as path from "path";

export class BackendStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const amplifyApi = new AmplifyGraphqlApi(this, "MyNewApi", {
      definition: AmplifyGraphqlDefinition.combine([
        AmplifyGraphqlDefinition.fromString(
          `
            type Todo @model @auth(rules: [{ allow: public }]) {
              title: String
            }
          `,
          {
            dbType: "DYNAMODB",
            provisionStrategy: "DEFAULT",
          },
        ),
        AmplifyGraphqlDefinition.fromString(
          `
            type Blog @model @auth(rules: [{ allow: public }]) {
              title: String
              content: String
              authors: [String]
            }
          `,
          {
            dbType: "DYNAMODB",
            provisionStrategy: "IMPORTED_AMPLIFY_TABLE",
          },
        ),
      ]),
      importedAmplifyDynamoDBTableMap: {
        // existing table
        Blog: 'Blog-xxxx-NONE',
      },
      authorizationModes: {
        defaultAuthorizationMode: "API_KEY",
        apiKeyConfig: {
          expires: cdk.Duration.days(30),
        },
      },
    });
  }
}

Issue #, if available

N/A

Description of how you validated changes

• Manual testing
• Unit tests, more to come in future PRs
• This is merging to a feature branch and E2E tests will be added with a separate PR

Checklist

• PR description included
• yarn test passes
• Tests are changed or added

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[palpatim]

We should also have multi-strategy tests. One case should ensure that a model that uses a different strategy throws an error if it is included in the importedAmplifyDynamoDBTableMap. Ideally, the error would note that the strategy is invalid, rather than a generic "missing" or "invalid" error. E.g., from your generator test below:

dataSourceStrategies: {
        Comment: DDB_DEFAULT_DATASOURCE_STRATEGY,
        Post: DDB_AMPLIFY_MANAGED_DATASOURCE_STRATEGY,
        Author: IMPORTED_DDB_AMPLIFY_MANAGED_DATASOURCE_STRATEGY,
      },
      importedAmplifyDynamoDBTableMap: {
        Author: 'Author-myApiId-myEnv',
      },

If you add Post to the map, we'd hope to see an error like "Table mapping includes models that do not use an imported strategy (Post)." or similar

[palpatim]

Suggested change

	* Type predicate that returns true if `obj` is a AmplifyDynamoDbModelDataSourceStrategy
	* Type predicate that returns true if `obj` is an ImportedAmplifyDynamoDbModelDataSourceStrategy

[palpatim]

Piling onto my above comments -- here you check for the existence of the importedTableMap, but don't validate the strategy. If we have conditions that can result in inconsistency b/t strategy & mapping, this is a source of potential future bugs.

[palpatim]

1. rather than inlining this big if block, can we refactor to a standalone function to make the "Create" case a bit easier to parse?
2. I don't see anything to suggest otherwise, but please confirm that this won't cause any issues with the Tagging support for Amplify-managed tables that we're introducing in fix: add tags to dynamodb tables #2694

[dpilch]

1. Will do.
2. I don't see any issues here, but I'll add a test to cover this case before merging to main.

[palpatim]

What validation needs to be added?

[dpilch]

The validation is to ensure the DDB properties align (Example: KeySchema, SSESpecification, etc.). WIP PR: #2696

[palpatim]

I assume the @ts-expect-error is to suppress the compile warning about the missing tableName attribute?

[dpilch]

Yes, updated to clarify

[phani-srikar]

Should we turn this "empty imported table name" scenario handling into a validation check and fail instead of treating this as a greenfield scenario?

[dpilch]

This would actually fail with No resource generator assigned for Post with dbType DYNAMODB. The error message could be improved though. I can tackle this in the next PR.

[phani-srikar]

minor nit for next PR: (since you already have a TODO up there):
Can combine above two lines to console.log('Fetching current state of table ${tableDef.tableName}'); to make it more readable in the logs.

[dpilch]

I'll update this in the next PR.