feat(rds): add engineVersion to DatabaseCluster (#2698)

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

Author: joehillen

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
    *
@@ -292,6 +299,7 @@ export class DatabaseCluster extends DatabaseClusterBase {
     const cluster = new CfnDBCluster(this, 'Resource', {
       // Basic
       engine: props.engine.name,
+      engineVersion: props.engineVersion,
       dbClusterIdentifier: props.clusterIdentifier,
       dbSubnetGroupName: subnetGroup.ref,
       vpcSecurityGroupIds: [this.securityGroupId],
@@ -349,6 +357,7 @@ 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() {