feat(cdk): Add support for UseOnlineResharding with UpdatePolicies (#881)

Author: ZeldoKavira

Diff for: packages/@aws-cdk/cdk/lib/cloudformation/resource-policy.ts

@@ -124,6 +124,12 @@ export interface UpdatePolicy {
    */
   autoScalingScheduledAction?: AutoScalingScheduledAction;
 
+  /**
+   * To modify a replication group's shards by adding or removing shards, rather than replacing the entire
+   * AWS::ElastiCache::ReplicationGroup resource, use the UseOnlineResharding update policy.
+   */
+  useOnlineResharding?: boolean;
+
 }
 
 /**

Diff for: packages/@aws-cdk/cdk/test/cloudformation/test.resource.ts

@@ -170,7 +170,7 @@ export = {
 
     r1.options.creationPolicy = { autoScalingCreationPolicy: { minSuccessfulInstancesPercent: 10 } };
     // tslint:disable-next-line:max-line-length
-    r1.options.updatePolicy = { autoScalingScheduledAction: { ignoreUnmodifiedGroupSizeProperties: false }, autoScalingReplacingUpdate: { willReplace: true } };
+    r1.options.updatePolicy = { autoScalingScheduledAction: { ignoreUnmodifiedGroupSizeProperties: false }, autoScalingReplacingUpdate: { willReplace: true }};
     r1.options.deletionPolicy = DeletionPolicy.Retain;
 
     test.deepEqual(stack.toCloudFormation(), {
@@ -180,7 +180,7 @@ export = {
           CreationPolicy: { AutoScalingCreationPolicy: { MinSuccessfulInstancesPercent: 10 } },
           UpdatePolicy: {
             AutoScalingScheduledAction: { IgnoreUnmodifiedGroupSizeProperties: false },
-            AutoScalingReplacingUpdate: { WillReplace: true }
+            AutoScalingReplacingUpdate: { WillReplace: true },
           },
           DeletionPolicy: 'Retain'
         }
@@ -190,6 +190,26 @@ export = {
     test.done();
   },
 
+  'update policies UseOnlineResharding flag'(test: Test) {
+    const stack = new Stack();
+    const r1 = new Resource(stack, 'Resource', { type: 'Type' });
+
+    r1.options.updatePolicy = { useOnlineResharding: true };
+
+    test.deepEqual(stack.toCloudFormation(), {
+      Resources: {
+        Resource: {
+          Type: 'Type',
+          UpdatePolicy: {
+            UseOnlineResharding: true,
+          },
+        }
+      }
+    });
+
+    test.done();
+  },
+
   'metadata can be set on a resource'(test: Test) {
     const stack = new Stack();
     const r1 = new Resource(stack, 'Resource', { type: 'Type' });