fix(rds): allow creating Proxies for imported resources

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

@@ -154,6 +154,7 @@ interface MysqlClusterEngineBaseProps {
 }
 
 abstract class MySqlClusterEngineBase extends ClusterEngineBase {
+  public readonly engineFamily = 'MYSQL';
   public readonly supportedLogTypes: string[] = ['error', 'general', 'slowquery', 'audit'];
 
   constructor(props: MysqlClusterEngineBaseProps) {
@@ -493,6 +494,7 @@ class AuroraPostgresClusterEngine extends ClusterEngineBase {
    */
   private static readonly S3_EXPORT_FEATURE_NAME = 's3Export';
 
+  public readonly engineFamily = 'POSTGRESQL';
   public readonly supportedLogTypes: string[] = ['postgresql'];
 
   constructor(version?: AuroraPostgresEngineVersion) {

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

@@ -1,6 +1,7 @@
 import * as ec2 from '@aws-cdk/aws-ec2';
 import * as secretsmanager from '@aws-cdk/aws-secretsmanager';
 import { IResource } from '@aws-cdk/core';
+import { IClusterEngine } from './cluster-engine';
 import { Endpoint } from './endpoint';
 import { DatabaseProxy, DatabaseProxyOptions } from './proxy';
 
@@ -35,6 +36,12 @@ export interface IDatabaseCluster extends IResource, ec2.IConnectable, secretsma
    */
   readonly instanceEndpoints: Endpoint[];
 
+  /**
+   * The engine of this Cluster.
+   * May be not known for imported Clusters if it wasn't provided explicitly.
+   */
+  readonly engine?: IClusterEngine;
+
   /**
    * Add a new db proxy to this cluster.
    */
@@ -92,4 +99,11 @@ export interface DatabaseClusterAttributes {
    * @default - no instance endpoints
    */
   readonly instanceEndpointAddresses?: string[];
+
+  /**
+   * The engine of the existing Cluster.
+   *
+   * @default - the imported Cluster's engine is unknown
+   */
+  readonly engine?: IClusterEngine;
 }

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

@@ -281,7 +281,11 @@ export abstract class DatabaseClusterBase extends Resource implements IDatabaseC
  * Abstract base for ``DatabaseCluster`` and ``DatabaseClusterFromSnapshot``
  */
 abstract class DatabaseClusterNew extends DatabaseClusterBase {
-
+  /**
+   * The engine for this Cluster.
+   * Never undefined.
+   */
+  public readonly engine?: IClusterEngine;
   public readonly instanceIdentifiers: string[] = [];
   public readonly instanceEndpoints: Endpoint[] = [];
 
@@ -331,6 +335,7 @@ abstract class DatabaseClusterNew extends DatabaseClusterBase {
 
     const clusterParameterGroup = props.parameterGroup ?? clusterEngineBindConfig.parameterGroup;
     const clusterParameterGroupConfig = clusterParameterGroup?.bindToCluster({});
+    this.engine = props.engine;
 
     this.newCfnProps = {
       // Basic
@@ -359,6 +364,7 @@ abstract class DatabaseClusterNew extends DatabaseClusterBase {
 class ImportedDatabaseCluster extends DatabaseClusterBase implements IDatabaseCluster {
   public readonly clusterIdentifier: string;
   public readonly connections: ec2.Connections;
+  public readonly engine?: IClusterEngine;
 
   private readonly _clusterEndpoint?: Endpoint;
   private readonly _clusterReadEndpoint?: Endpoint;
@@ -375,6 +381,7 @@ class ImportedDatabaseCluster extends DatabaseClusterBase implements IDatabaseCl
       securityGroups: attrs.securityGroups,
       defaultPort,
     });
+    this.engine = attrs.engine;
 
     this._clusterEndpoint = (attrs.clusterEndpointAddress && attrs.port) ? new Endpoint(attrs.clusterEndpointAddress, attrs.port) : undefined;
     this._clusterReadEndpoint = (attrs.readerEndpointAddress && attrs.port) ? new Endpoint(attrs.readerEndpointAddress, attrs.port) : undefined;

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

@@ -28,4 +28,15 @@ export interface IEngine {
    *   (which means the major version of the engine is also not known)
    */
   readonly parameterGroupFamily?: string;
+
+  /**
+   * The family this engine belongs to,
+   * like "MYSQL", or "POSTGRESQL".
+   * This property is used when creating a Database Proxy.
+   * Most engines don't belong to any family
+   * (and because of that, you can't create Database Proxies for their Clusters or Instances).
+   *
+   * @default - the engine doesn't belong to any family
+   */
+  readonly engineFamily?: string;
 }

packages/@aws-cdk/aws-rds/lib/instance-engine.ts

@@ -109,6 +109,7 @@ interface InstanceEngineBaseProps {
   readonly multiUserRotationApplication: secretsmanager.SecretRotationApplication;
   readonly version?: EngineVersion;
   readonly parameterGroupFamily?: string;
+  readonly engineFamily?: string;
   readonly features?: InstanceEngineFeatures;
 }
 
@@ -118,6 +119,7 @@ abstract class InstanceEngineBase implements IInstanceEngine {
   public readonly parameterGroupFamily?: string;
   public readonly singleUserRotationApplication: secretsmanager.SecretRotationApplication;
   public readonly multiUserRotationApplication: secretsmanager.SecretRotationApplication;
+  public readonly engineFamily?: string;
 
   private readonly features?: InstanceEngineFeatures;
 
@@ -129,6 +131,7 @@ abstract class InstanceEngineBase implements IInstanceEngine {
     this.engineVersion = props.version;
     this.parameterGroupFamily = props.parameterGroupFamily ??
       (this.engineVersion ? `${this.engineType}${this.engineVersion.majorVersion}` : undefined);
+    this.engineFamily = props.engineFamily;
   }
 
   public bindToInstance(_scope: core.Construct, options: InstanceEngineBindOptions): InstanceEngineConfig {
@@ -391,6 +394,7 @@ class MySqlInstanceEngine extends InstanceEngineBase {
           majorVersion: version.mysqlMajorVersion,
         }
         : undefined,
+      engineFamily: 'MYSQL',
     });
   }
 }
@@ -586,6 +590,7 @@ class PostgresInstanceEngine extends InstanceEngineBase {
         }
         : undefined,
       features: version ? version?._features : { s3Import: 's3Import' },
+      engineFamily: 'POSTGRESQL',
     });
   }
 }

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

@@ -50,6 +50,13 @@ export interface IDatabaseInstance extends IResource, ec2.IConnectable, secretsm
    */
   readonly instanceEndpoint: Endpoint;
 
+  /**
+   * The engine of this database Instance.
+   * May be not known for imported Instances if it wasn't provided explicitly,
+   * or for read replicas.
+   */
+  readonly engine?: IInstanceEngine;
+
   /**
    * Add a new db proxy to this instance.
    */
@@ -90,6 +97,13 @@ export interface DatabaseInstanceAttributes {
    * The security groups of the instance.
    */
   readonly securityGroups: ec2.ISecurityGroup[];
+
+  /**
+   * The engine of the existing database Instance.
+   *
+   * @default - the imported Instance's engine is unknown
+   */
+  readonly engine?: IInstanceEngine;
 }
 
 /**
@@ -110,6 +124,7 @@ export abstract class DatabaseInstanceBase extends Resource implements IDatabase
       public readonly dbInstanceEndpointAddress = attrs.instanceEndpointAddress;
       public readonly dbInstanceEndpointPort = attrs.port.toString();
       public readonly instanceEndpoint = new Endpoint(attrs.instanceEndpointAddress, attrs.port);
+      public readonly engine = attrs.engine;
       protected enableIamAuthentication = true;
     }
 
@@ -769,6 +784,7 @@ export interface DatabaseInstanceSourceProps extends DatabaseInstanceNewProps {
  * A new source database instance (not a read replica)
  */
 abstract class DatabaseInstanceSource extends DatabaseInstanceNew implements IDatabaseInstance {
+  public readonly engine?: IInstanceEngine;
   /**
    * The AWS Secrets Manager secret attached to the instance.
    */
@@ -785,6 +801,7 @@ abstract class DatabaseInstanceSource extends DatabaseInstanceNew implements IDa
 
     this.singleUserRotationApplication = props.engine.singleUserRotationApplication;
     this.multiUserRotationApplication = props.engine.multiUserRotationApplication;
+    this.engine = props.engine;
 
     let { s3ImportRole, s3ExportRole } = setupS3ImportExport(this, props, true);
     const engineConfig = props.engine.bindToInstance(this, {

packages/@aws-cdk/aws-rds/lib/private/util.ts

@@ -1,7 +1,7 @@
 import * as iam from '@aws-cdk/aws-iam';
 import * as s3 from '@aws-cdk/aws-s3';
 import { Construct, CfnDeletionPolicy, CfnResource, RemovalPolicy } from '@aws-cdk/core';
-import { IInstanceEngine } from '../instance-engine';
+import { IEngine } from '../engine';
 
 /** Common base of `DatabaseInstanceProps` and `DatabaseClusterBaseProps` that has only the S3 props */
 export interface DatabaseS3ImportExportProps {
@@ -56,7 +56,7 @@ export function setupS3ImportExport(
   return { s3ImportRole, s3ExportRole };
 }
 
-export function engineDescription(engine: IInstanceEngine) {
+export function engineDescription(engine: IEngine) {
   return engine.engineType + (engine.engineVersion?.fullVersion ? `-${engine.engineVersion.fullVersion}` : '');
 }
 

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

@@ -3,8 +3,10 @@ import * as iam from '@aws-cdk/aws-iam';
 import * as secretsmanager from '@aws-cdk/aws-secretsmanager';
 import * as cdk from '@aws-cdk/core';
 import { IDatabaseCluster } from './cluster-ref';
+import { IEngine } from './engine';
 import { IDatabaseInstance } from './instance';
-import { CfnDBCluster, CfnDBInstance, CfnDBProxy, CfnDBProxyTargetGroup } from './rds.generated';
+import { engineDescription } from './private/util';
+import { CfnDBProxy, CfnDBProxyTargetGroup } from './rds.generated';
 
 /**
  * SessionPinningFilter
@@ -47,7 +49,7 @@ export class ProxyTarget {
    * @param instance RDS database instance
    */
   public static fromInstance(instance: IDatabaseInstance): ProxyTarget {
-    return new ProxyTarget(instance);
+    return new ProxyTarget(instance, undefined);
   }
 
   /**
@@ -59,34 +61,26 @@ export class ProxyTarget {
     return new ProxyTarget(undefined, cluster);
   }
 
-  private constructor(private readonly dbInstance?: IDatabaseInstance, private readonly dbCluster?: IDatabaseCluster) {}
+  private constructor(
+    private readonly dbInstance: IDatabaseInstance | undefined,
+    private readonly dbCluster: IDatabaseCluster | undefined) {
+  }
 
   /**
    * Bind this target to the specified database proxy.
    */
   public bind(_: DatabaseProxy): ProxyTargetConfig {
-    let engine: string | undefined;
-    if (this.dbCluster && this.dbInstance) {
-      throw new Error('Proxy cannot target both database cluster and database instance.');
-    } else if (this.dbCluster) {
-      engine = (this.dbCluster.node.defaultChild as CfnDBCluster).engine;
-    } else if (this.dbInstance) {
-      engine = (this.dbInstance.node.defaultChild as CfnDBInstance).engine;
+    const engine: IEngine | undefined = this.dbInstance?.engine ?? this.dbCluster?.engine;
+
+    if (!engine) {
+      const errorResource = this.dbCluster ?? this.dbInstance;
+      throw new Error(`Could not determine engine for proxy target '${errorResource?.node.path}'. ` +
+        'Please provide it explicitly when importing the resource');
     }
 
-    let engineFamily;
-    switch (engine) {
-      case 'aurora':
-      case 'aurora-mysql':
-      case 'mysql':
-        engineFamily = 'MYSQL';
-        break;
-      case 'aurora-postgresql':
-      case 'postgres':
-        engineFamily = 'POSTGRESQL';
-        break;
-      default:
-        throw new Error(`Unsupported engine type - ${engine}`);
+    const engineFamily = engine.engineFamily;
+    if (!engineFamily) {
+      throw new Error(`Engine '${engineDescription(engine)}' does not support proxies`);
     }
 
     return {
@@ -105,12 +99,14 @@ export interface ProxyTargetConfig {
    * The engine family of the database instance or cluster this proxy connects with.
    */
   readonly engineFamily: string;
+
   /**
    * The database instances to which this proxy connects.
    * Either this or `dbClusters` will be set and the other `undefined`.
    * @default - `undefined` if `dbClusters` is set.
    */
   readonly dbInstances?: IDatabaseInstance[];
+
   /**
    * The database clusters to which this proxy connects.
    * Either this or `dbInstances` will be set and the other `undefined`.