feat(rds): add engineVersion to DatabaseCluster

Without this change, CDK's RDS DatabaseCluster is not very useful
because you can only deploy the default versions
of the given database engine.

This change adds an optional prop `engineVersion`

fixes #2212

packages/@aws-cdk/aws-rds/lib/cluster.ts

@@ -19,6 +19,13 @@ export interface DatabaseClusterProps {
    */
   readonly engine: DatabaseClusterEngine;
 
+  /**
+   * What version of the database to start
+   *
+   * @default - The default for the engine is used.
+   */
+  readonly engineVersion?: string;
+
   /**
    * How many replicas/instances to create
    *
@@ -239,6 +246,14 @@ export class DatabaseCluster extends DatabaseClusterBase {
    */
   public readonly secret?: secretsmanager.ISecret;
 
+  /**
+   * The database version of the engine of this cluster
+   *
+   * @default - The default for the engine is used.
+   */
+  public readonly engineVersion?: string;
+
+
   /**
    * The database engine of this cluster
    */
@@ -288,10 +303,12 @@ export class DatabaseCluster extends DatabaseClusterBase {
     }
 
     this.secretRotationApplication = props.engine.secretRotationApplication;
+    this.engineVersion = props.engineVersion;
 
     const cluster = new CfnDBCluster(this, 'Resource', {
       // Basic
       engine: props.engine.name,
+      engineVersion: this.engineVersion,
       dbClusterIdentifier: props.clusterIdentifier,
       dbSubnetGroupName: subnetGroup.ref,
       vpcSecurityGroupIds: [this.securityGroupId],
@@ -349,6 +366,7 @@ export class DatabaseCluster extends DatabaseClusterBase {
       const instance = new CfnDBInstance(this, `Instance${instanceIndex}`, {
         // Link to cluster
         engine: props.engine.name,
+        engineVersion: props.engineVersion,
         dbClusterIdentifier: cluster.ref,
         dbInstanceIdentifier: instanceIdentifier,
         // Instance properties

packages/@aws-cdk/aws-rds/test/test.cluster.ts

@@ -266,6 +266,60 @@ export = {
     test.done();
 
   },
+
+  'create a cluster using a specific version of MySQL'(test: Test) {
+    // GIVEN
+    const stack = testStack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+
+    // WHEN
+    new DatabaseCluster(stack, 'Database', {
+      engine: DatabaseClusterEngine.AuroraMysql,
+      engineVersion: "5.7.mysql_aurora.2.04.4",
+      masterUser: {
+        username: 'admin'
+      },
+      instanceProps: {
+        instanceType: new ec2.InstanceTypePair(ec2.InstanceClass.Burstable2, ec2.InstanceSize.Small),
+        vpc
+      },
+    });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::RDS::DBCluster', {
+      Engine: "aurora-mysql",
+      EngineVersion: "5.7.mysql_aurora.2.04.4",
+    }));
+
+    test.done();
+  },
+
+  'create a cluster using a specific version of Postgresql'(test: Test) {
+    // GIVEN
+    const stack = testStack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+
+    // WHEN
+    new DatabaseCluster(stack, 'Database', {
+      engine: DatabaseClusterEngine.AuroraPostgresql,
+      engineVersion: "10.7",
+      masterUser: {
+        username: 'admin'
+      },
+      instanceProps: {
+        instanceType: new ec2.InstanceTypePair(ec2.InstanceClass.Burstable2, ec2.InstanceSize.Small),
+        vpc
+      },
+    });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::RDS::DBCluster', {
+      Engine: "aurora-postgresql",
+      EngineVersion: "10.7",
+    }));
+
+    test.done();
+  }
 };
 
 function testStack() {