fix(lambda): cannot use latest version in multiple CloudFront distributions

The error produced is around construct collision, i.e., "There is
already a Construct with name '$LATEST' in Function".

The fix is to cache the latest version on the instance.

fixes #4459

Author: Niranjan Jayakar

packages/@aws-cdk/aws-lambda/lib/event-invoke-config.ts

@@ -5,18 +5,19 @@ import { CfnEventInvokeConfig } from './lambda.generated';
 
 /**
  * Options to add an EventInvokeConfig to a function.
+ * @deprecated - use `new EventInvokeConfig()` instead
  */
 export interface EventInvokeConfigOptions {
   /**
    * The destination for failed invocations.
-   *
+   * @deprecated use `new EventInvokeConfig()` instead to define a new event invoke configuration
    * @default - no destination
    */
   readonly onFailure?: IDestination;
 
   /**
    * The destination for successful invocations.
-   *
+   * @deprecated use `new EventInvokeConfig()` instead to define a new event invoke configuration
    * @default - no destination
    */
   readonly onSuccess?: IDestination;
@@ -27,7 +28,7 @@ export interface EventInvokeConfigOptions {
    *
    * Minimum: 60 seconds
    * Maximum: 6 hours
-   *
+   * @deprecated use `new EventInvokeConfig()` instead to define a new event invoke configuration
    * @default Duration.hours(6)
    */
   readonly maxEventAge?: Duration;
@@ -37,7 +38,7 @@ export interface EventInvokeConfigOptions {
    *
    * Minimum: 0
    * Maximum: 2
-   *
+   * @deprecated use `new EventInvokeConfig()` instead to define a new event invoke configuration
    * @default 2
    */
   readonly retryAttempts?: number;
@@ -46,7 +47,7 @@ export interface EventInvokeConfigOptions {
 /**
  * Properties for an EventInvokeConfig
  */
-export interface EventInvokeConfigProps extends EventInvokeConfigOptions {
+export interface EventInvokeConfigProps {
   /**
    * The Lambda function
    */
@@ -58,6 +59,41 @@ export interface EventInvokeConfigProps extends EventInvokeConfigOptions {
    * @default - latest version
    */
   readonly qualifier?: string;
+
+  /**
+   * The destination for failed invocations.
+   *
+   * @default - no destination
+   */
+  readonly onFailure?: IDestination;
+
+  /**
+   * The destination for successful invocations.
+   *
+   * @default - no destination
+   */
+  readonly onSuccess?: IDestination;
+
+  /**
+   * The maximum age of a request that Lambda sends to a function for
+   * processing.
+   *
+   * Minimum: 60 seconds
+   * Maximum: 6 hours
+   *
+   * @default Duration.hours(6)
+   */
+  readonly maxEventAge?: Duration;
+
+  /**
+   * The maximum number of times to retry when the function returns an error.
+   *
+   * Minimum: 0
+   * Maximum: 2
+   *
+   * @default 2
+   */
+  readonly retryAttempts?: number;
 }
 
 /**

packages/@aws-cdk/aws-lambda/lib/function-base.ts

@@ -194,6 +194,8 @@ export abstract class FunctionBase extends Resource implements IFunction {
    */
   protected _connections?: ec2.Connections;
 
+  private _latestVersion?: LatestVersion;
+
   /**
    * Adds a permission to the Lambda resource policy.
    * @param id The id ƒor the permission construct
@@ -245,7 +247,10 @@ export abstract class FunctionBase extends Resource implements IFunction {
 
   public get latestVersion(): IVersion {
     // Dynamic to avoid infinite recursion when creating the LatestVersion instance...
-    return new LatestVersion(this);
+    if (!this._latestVersion) {
+      this._latestVersion = new LatestVersion(this);
+    }
+    return this._latestVersion;
   }
 
   /**

packages/@aws-cdk/aws-lambda/test/test.function.ts

@@ -359,6 +359,31 @@ export = testCase({
     test.done();
   },
 
+  'multiple calls to latestVersion returns the same version'(test: Test) {
+    const stack = new cdk.Stack();
+
+    const fn = new lambda.Function(stack, 'MyLambda', {
+      code: new lambda.InlineCode('hello()'),
+      handler: 'index.hello',
+      runtime: lambda.Runtime.NODEJS_10_X,
+    });
+
+    const version1 = fn.latestVersion;
+    const version2 = fn.latestVersion;
+
+    const expectedArn = {
+      'Fn::Join': ['', [
+        { 'Fn::GetAtt': ['MyLambdaCCE802FB', 'Arn'] },
+        ':$LATEST',
+      ]],
+    };
+    test.equal(version1, version2);
+    test.deepEqual(stack.resolve(version1.functionArn), expectedArn);
+    test.deepEqual(stack.resolve(version2.functionArn), expectedArn);
+
+    test.done();
+  },
+
   'currentVersion': {
     // see test.function-hash.ts for more coverage for this
     'logical id of version is based on the function hash'(test: Test) {