feat: Create StringParam the normal way, and use Custom Resource for replica

This is more like Secrets and DynamoDB replica.

Author: nickwillan

.projen/tasks.json

@@ -4,7 +4,7 @@ const project = new awscdk.AwsCdkConstructLibrary({
   authorAddress: 'https://github.com/nickwillan',
   keywords: ['aws', 'cdk', 'parameter', 'serverless,', 'ssm'],
   description: 'CDK Contstruct that creates a globally replicated Systems Manager String Parameter.',
-  majorVersion: 2,
+  majorVersion: 3,
   cdkVersion: '2.190.0',
   constructsVersion: '10.4.2',
   defaultReleaseBranch: 'main',

.projenrc.ts

@@ -1,26 +1,29 @@
 import { PolicyStatement, Effect } from 'aws-cdk-lib/aws-iam';
-import { StringParameterProps } from 'aws-cdk-lib/aws-ssm';
+import { StringParameter, StringParameterProps } from 'aws-cdk-lib/aws-ssm';
 import { AwsCustomResource, AwsCustomResourcePolicy, PhysicalResourceId } from 'aws-cdk-lib/custom-resources';
 import { Construct } from 'constructs';
 
 /**
  * GlobalStringParameterProps defines the properties for the GlobalStringParameter construct.
  *
  * @interface GlobalStringParameterProps
+ * @property {StringParameter} [existingStringParamObj] - An existing SSM String Parameter object to use instead of creating a new one.
  * @property {StringParameterProps} parameterProps - The properties for the SSM String Parameter to be created.
  * @property {{ [key: string]: string }} [tags] - Optional tags to be added to the SSM Parameter.
- * @property {string[]} regions - The list of AWS regions where the SSM Parameter should be created.
+ * @property {string[]} replicaRegions - The list of AWS regions where the SSM Parameter should be replicated.
  */
 export interface GlobalStringParameterProps {
+  readonly existingStringParamObj?: StringParameter;
   readonly parameterProps: StringParameterProps;
   readonly tags?: { [key: string]: string }[];
-  readonly regions: string[];
+  readonly replicaRegions: string[];
 }
 
 /**
  * Creates an SSM Parameter in multiple regions using Custom Resources
  */
 export class GlobalStringParameter extends Construct {
+  public readonly stringParameter: StringParameter;
   constructor(scope: Construct, id: string, props: GlobalStringParameterProps) {
     super(scope, id);
 
@@ -32,11 +35,23 @@ export class GlobalStringParameter extends Construct {
       throw new Error('stringValue must be specified');
     }
 
-    if (!props.regions || props.regions.length === 0) {
+    if (!props.replicaRegions || props.replicaRegions.length === 0) {
       throw new Error('At least one region must be specified');
     }
 
-    props.regions.forEach((region) => {
+    const currentRegion = process.env.CDK_DEFAULT_REGION;
+    if (props.replicaRegions.includes(currentRegion!)) {
+      throw new Error('The current region cannot be included in the replicaRegions list');
+    }
+
+    if (props.existingStringParamObj) {
+      this.stringParameter = props.existingStringParamObj;
+    } else {
+      this.stringParameter = new StringParameter(this, 'GlobalSSMParameter', props.parameterProps);
+    }
+
+    // Create a custom resource for each replica region
+    props.replicaRegions.forEach((region) => {
       const resource = new AwsCustomResource(this, `GlobalSSMParameter-${region}`, {
         onCreate: {
           service: 'SSM',

API.md

@@ -1,6 +1,6 @@
 import * as cdk from 'aws-cdk-lib';
 import { Template } from 'aws-cdk-lib/assertions';
-import { ParameterTier, ParameterDataType } from 'aws-cdk-lib/aws-ssm';
+import { ParameterTier, ParameterDataType, StringParameter } from 'aws-cdk-lib/aws-ssm';
 import { GlobalStringParameter } from '../src/index';
 
 describe('GlobalParameter', () => {
@@ -13,7 +13,7 @@ describe('GlobalParameter', () => {
         parameterProps: {
           stringValue: 'testValue',
         } as any,
-        regions: ['us-east-1'],
+        replicaRegions: ['us-east-1'],
       });
     }).toThrow('parameterName must be specified');
   });
@@ -27,12 +27,12 @@ describe('GlobalParameter', () => {
         parameterProps: {
           parameterName: 'testParameter',
         } as any,
-        regions: ['us-east-1'],
+        replicaRegions: ['us-east-1'],
       });
     }).toThrow('stringValue must be specified');
   });
 
-  it('throws an error if no regions are specified', () => {
+  it('throws an error if the current region is included in the replicaRegions list', () => {
     const app = new cdk.App();
     const stack = new cdk.Stack(app, 'TestStack');
 
@@ -42,7 +42,22 @@ describe('GlobalParameter', () => {
           parameterName: 'testParameter',
           stringValue: 'testValue',
         },
-        regions: [],
+        replicaRegions: ['us-east-1', process.env.CDK_DEFAULT_REGION!],
+      });
+    }).toThrow('The current region cannot be included in the replicaRegions list');
+  });
+
+  it('throws an error if no replicaRegions are specified', () => {
+    const app = new cdk.App();
+    const stack = new cdk.Stack(app, 'TestStack');
+
+    expect(() => {
+      new GlobalStringParameter(stack, 'TestGlobalParameter', {
+        parameterProps: {
+          parameterName: 'testParameter',
+          stringValue: 'testValue',
+        },
+        replicaRegions: [],
       });
     }).toThrow('At least one region must be specified');
   });
@@ -60,18 +75,57 @@ describe('GlobalParameter', () => {
         dataType: ParameterDataType.TEXT,
         allowedPattern: '.*',
       },
-      regions: ['us-east-1'],
+      replicaRegions: ['us-east-1'],
     });
 
     const template = Template.fromStack(stack);
 
     console.log(JSON.stringify(template.toJSON(), null, 2));
 
     template.hasResourceProperties('Custom::AWS', {});
+
+    template.hasResourceProperties('AWS::SSM::Parameter', {
+      Type: 'String',
+      Description: 'Test description',
+      Tier: 'Standard',
+      DataType: 'text',
+      AllowedPattern: '.*',
+    });
   });
 });
 
-it('creates, updates, and deletes SSM parameters in multiple regions', () => {
+it('creates an SSM parameter with existing paramaters', () => {
+  const app = new cdk.App();
+  const stack = new cdk.Stack(app, 'TestStack');
+
+  const existingStringParamObj = new StringParameter(new cdk.Stack(app, 'OrigStack'), 'ExistingStringParameter', {
+    parameterName: 'existingParameter',
+    stringValue: 'existingValue',
+  });
+
+  new GlobalStringParameter(stack, 'TestGlobalParameter', {
+    existingStringParamObj,
+    parameterProps: {
+      parameterName: 'testParameter',
+      stringValue: 'testValue',
+      description: 'Test description',
+      tier: ParameterTier.STANDARD,
+      dataType: ParameterDataType.TEXT,
+      allowedPattern: '.*',
+    },
+    replicaRegions: ['us-east-1'],
+  });
+
+  const template = Template.fromStack(stack);
+
+  console.log(JSON.stringify(template.toJSON(), null, 2));
+
+  template.hasResourceProperties('Custom::AWS', {});
+
+  template.resourceCountIs('AWS::SSM::Parameter', 0);
+});
+
+it('creates, updates, and deletes SSM parameters in multiple replicaRegions', () => {
   const app = new cdk.App();
   const stack = new cdk.Stack(app, 'TestStack');
 
@@ -80,7 +134,7 @@ it('creates, updates, and deletes SSM parameters in multiple regions', () => {
       parameterName: 'testParameter',
       stringValue: 'testValue',
     },
-    regions: ['us-east-1', 'us-west-2'],
+    replicaRegions: ['us-east-1', 'us-west-2'],
   });
 
   const template = Template.fromStack(stack);
@@ -98,7 +152,7 @@ it('adds a policy to the grantPrincipal', () => {
       parameterName: 'testParameter',
       stringValue: 'testValue',
     },
-    regions: ['us-east-1'],
+    replicaRegions: ['us-east-1'],
   });
 
   const template = Template.fromStack(stack);