feat(rds): Validate log types for clusters (#9797)

This builds on #9772 to add validation for the types of logs that are available
on each cluster type (by engine).

Notes:
* Currently a draft: I want feedback on this approach before either adding some
  constants for ease-of-use and porting a similar approach to instances.
* This is built off of #9772, so includes the changes from #9772 while it is
  pending a push/merge.
* Added pr-linter/exempt-readme label (for now) as the current change is validation only.
  Will add README changes if/when this includes some usable constants.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

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

@@ -61,6 +61,9 @@ export interface IClusterEngine extends IEngine {
   /** The application used by this engine to perform rotation for a multi-user scenario. */
   readonly multiUserRotationApplication: secretsmanager.SecretRotationApplication;
 
+  /** The log types that are available with this engine type */
+  readonly supportedLogTypes: string[];
+
   /**
    * Method called when the engine is used to create a new cluster.
    */
@@ -81,6 +84,7 @@ abstract class ClusterEngineBase implements IClusterEngine {
   public readonly parameterGroupFamily?: string;
   public readonly singleUserRotationApplication: secretsmanager.SecretRotationApplication;
   public readonly multiUserRotationApplication: secretsmanager.SecretRotationApplication;
+  public abstract readonly supportedLogTypes: string[];
 
   private readonly defaultPort?: number;
 
@@ -116,6 +120,8 @@ interface MysqlClusterEngineBaseProps {
 }
 
 abstract class MySqlClusterEngineBase extends ClusterEngineBase {
+  public readonly supportedLogTypes: string[] = ['error', 'general', 'slowquery', 'audit'];
+
   constructor(props: MysqlClusterEngineBaseProps) {
     super({
       ...props,
@@ -408,6 +414,8 @@ export interface AuroraPostgresClusterEngineProps {
 }
 
 class AuroraPostgresClusterEngine extends ClusterEngineBase {
+  public readonly supportedLogTypes: string[] = ['postgresql'];
+
   constructor(version?: AuroraPostgresEngineVersion) {
     super({
       engineType: 'aurora-postgresql',

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

@@ -613,13 +613,20 @@ export class DatabaseCluster extends DatabaseClusterBase {
   }
 
   private setLogRetention(props: DatabaseClusterProps) {
-    if (props.cloudwatchLogsExports && props.cloudwatchLogsRetention) {
-      for (const log of props.cloudwatchLogsExports) {
-        new lambda.LogRetention(this, `LogRetention${log}`, {
-          logGroupName: `/aws/rds/cluster/${this.clusterIdentifier}/${log}`,
-          retention: props.cloudwatchLogsRetention,
-          role: props.cloudwatchLogsRetentionRole,
-        });
+    if (props.cloudwatchLogsExports) {
+      const unsupportedLogTypes = props.cloudwatchLogsExports.filter(logType => !props.engine.supportedLogTypes.includes(logType));
+      if (unsupportedLogTypes.length > 0) {
+        throw new Error(`Unsupported logs for the current engine type: ${unsupportedLogTypes.join(',')}`);
+      }
+
+      if (props.cloudwatchLogsRetention) {
+        for (const log of props.cloudwatchLogsExports) {
+          new lambda.LogRetention(this, `LogRetention${log}`, {
+            logGroupName: `/aws/rds/cluster/${this.clusterIdentifier}/${log}`,
+            retention: props.cloudwatchLogsRetention,
+            role: props.cloudwatchLogsRetentionRole,
+          });
+        }
       }
     }
   }

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

@@ -107,4 +107,12 @@ export = {
 
     test.done();
   },
-};
+
+  'supported log types'(test: Test) {
+    const mysqlLogTypes = ['error', 'general', 'slowquery', 'audit'];
+    test.deepEqual(DatabaseClusterEngine.aurora({ version: AuroraEngineVersion.VER_1_22_2 }).supportedLogTypes, mysqlLogTypes);
+    test.deepEqual(DatabaseClusterEngine.auroraMysql({ version: AuroraMysqlEngineVersion.VER_2_08_1 }).supportedLogTypes, mysqlLogTypes);
+    test.deepEqual(DatabaseClusterEngine.auroraPostgres({ version: AuroraPostgresEngineVersion.VER_9_6_9 }).supportedLogTypes, ['postgresql']);
+    test.done();
+  },
+}

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

@@ -1155,6 +1155,29 @@ export = {
     test.done();
   },
 
+  'throws if given unsupported CloudWatch log exports'(test: Test) {
+    // GIVEN
+    const stack = testStack();
+    const vpc = new ec2.Vpc(stack, 'VPC');
+
+    test.throws(() => {
+      new DatabaseCluster(stack, 'Database', {
+        engine: DatabaseClusterEngine.AURORA,
+        masterUser: {
+          username: 'admin',
+          password: cdk.SecretValue.plainText('tooshort'),
+        },
+        instanceProps: {
+          instanceType: ec2.InstanceType.of(ec2.InstanceClass.BURSTABLE2, ec2.InstanceSize.SMALL),
+          vpc,
+        },
+        cloudwatchLogsExports: ['error', 'general', 'slowquery', 'audit', 'thislogdoesnotexist', 'neitherdoesthisone'],
+      });
+    }, /Unsupported logs for the current engine type: thislogdoesnotexist,neitherdoesthisone/);
+
+    test.done();
+  },
+
   'does not throw (but adds a node error) if a (dummy) VPC does not have sufficient subnets'(test: Test) {
     // GIVEN
     const stack = testStack();