chore(lambda-nodejs): do not add unused environment variable by default for sdk v3 lambda runtimes

packages/aws-cdk-lib/aws-lambda-nodejs/README.md

@@ -79,7 +79,9 @@ All properties of `lambda.Function` can be used to customize the underlying `lam
 See also the [AWS Lambda construct library](https://github.com/aws/aws-cdk/tree/main/packages/aws-cdk-lib/aws-lambda).
 
 The `NodejsFunction` construct automatically [reuses existing connections](https://docs.aws.amazon.com/sdk-for-javascript/v2/developer-guide/node-reusing-connections.html)
-when working with the AWS SDK for JavaScript. Set the `awsSdkConnectionReuse` prop to `false` to disable it.
+when working with the AWS SDK v2 for JavaScript. Set the `awsSdkConnectionReuse` prop to `false` to disable it.
+
+The AWS SDK v3 for JavaScript does not include the environment variable set by `awsSdkConnectionReuse`. See [this guide](https://docs.aws.amazon.com/sdk-for-javascript/v3/developer-guide/node-reusing-connections.html) for information about reusing connections. Therefore, for runtimes >= Node 18, which include SDK v3, the prop defaults to `false`, and must be explicitly set to `true` in order for the environment variable to be set.
 
 ## Runtime
 

packages/aws-cdk-lib/aws-lambda-nodejs/lib/bundling.ts

@@ -4,7 +4,7 @@ import { IConstruct } from 'constructs';
 import { PackageInstallation } from './package-installation';
 import { LockFile, PackageManager } from './package-manager';
 import { BundlingOptions, OutputFormat, SourceMapMode } from './types';
-import { exec, extractDependencies, findUp, getTsconfigCompilerOptions } from './util';
+import { exec, extractDependencies, findUp, getTsconfigCompilerOptions, isSdkV2Runtime } from './util';
 import { Architecture, AssetCode, Code, Runtime } from '../../aws-lambda';
 import * as cdk from '../../core';
 
@@ -442,24 +442,6 @@ function toCliArgs(esbuildArgs: { [key: string]: string | boolean }): string {
   return args.join(' ');
 }
 
-/**
- * Detect if a given Node.js runtime uses SDKv2
- */
-function isSdkV2Runtime(runtime: Runtime): boolean {
-  const sdkV2RuntimeList = [
-    Runtime.NODEJS,
-    Runtime.NODEJS_4_3,
-    Runtime.NODEJS_6_10,
-    Runtime.NODEJS_8_10,
-    Runtime.NODEJS_10_X,
-    Runtime.NODEJS_12_X,
-    Runtime.NODEJS_14_X,
-    Runtime.NODEJS_16_X,
-  ];
-
-  return sdkV2RuntimeList.some((r) => {return r.family === runtime.family && r.name === runtime.name;});
-}
-
 /**
  * Detect if a given Node.js runtime supports ESM (ECMAScript modules)
  */

packages/aws-cdk-lib/aws-lambda-nodejs/lib/function.ts

@@ -4,10 +4,10 @@ import { Construct } from 'constructs';
 import { Bundling } from './bundling';
 import { LockFile } from './package-manager';
 import { BundlingOptions } from './types';
-import { callsites, findUpMultiple } from './util';
+import { callsites, findUpMultiple, isSdkV2Runtime } from './util';
 import { Architecture } from '../../aws-lambda';
 import * as lambda from '../../aws-lambda';
-import { FeatureFlags } from '../../core';
+import { Annotations, FeatureFlags } from '../../core';
 import { LAMBDA_NODEJS_USE_LATEST_RUNTIME } from '../../cx-api';
 
 /**
@@ -43,15 +43,19 @@ export interface NodejsFunctionProps extends lambda.FunctionOptions {
   readonly runtime?: lambda.Runtime;
 
   /**
+   * The `AWS_NODEJS_CONNECTION_REUSE_ENABLED` environment variable does not exist in the AWS SDK for JavaScript v3.
+   *
+   * This prop will be deprecated when the Lambda Node16 runtime is deprecated on June 12, 2024.
+   *
+   * Info for Node 16 runtimes / SDK v2 users:
+   *
    * Whether to automatically reuse TCP connections when working with the AWS
-   * SDK for JavaScript.
+   * SDK for JavaScript v2.
    *
    * This sets the `AWS_NODEJS_CONNECTION_REUSE_ENABLED` environment variable
    * to `1`.
    *
-   * @see https://docs.aws.amazon.com/sdk-for-javascript/v2/developer-guide/node-reusing-connections.html
-   *
-   * @default true
+   * @default - false (obsolete) for runtimes >= Node 18, true for runtimes <= Node 16.
    */
   readonly awsSdkConnectionReuse?: boolean;
 
@@ -116,9 +120,16 @@ export class NodejsFunction extends lambda.Function {
       handler: handler.indexOf('.') !== -1 ? `${handler}` : `index.${handler}`,
     });
 
-    // Enable connection reuse for aws-sdk
-    if (props.awsSdkConnectionReuse ?? true) {
-      this.addEnvironment('AWS_NODEJS_CONNECTION_REUSE_ENABLED', '1', { removeInEdge: true });
+    // Enable connection reuse for aws-sdk v2, do not set for sdk v3
+    if (isSdkV2Runtime(runtime)) {
+      if (props.awsSdkConnectionReuse ?? true) {
+        this.addEnvironment('AWS_NODEJS_CONNECTION_REUSE_ENABLED', '1', { removeInEdge: true });
+      }
+    } else {
+      if (props.awsSdkConnectionReuse) {
+        Annotations.of(scope).addWarningV2('aws-cdk-lib/aws-lambda-nodejs:unusedSdkEvironmentVariable', 'The AWS_NODEJS_CONNECTION_REUSE_ENABLED environment variable does not exist in SDK v3. You have explicitly set `awsSdkConnectionReuse`; please make sure this is intentional.');
+        this.addEnvironment('AWS_NODEJS_CONNECTION_REUSE_ENABLED', '1', { removeInEdge: true });
+      }
     }
   }
 

packages/aws-cdk-lib/aws-lambda-nodejs/lib/util.ts

@@ -1,6 +1,7 @@
 import { spawnSync, SpawnSyncOptions } from 'child_process';
 import * as fs from 'fs';
 import * as path from 'path';
+import { Runtime } from '../../aws-lambda';
 
 export interface CallSite {
   getThis(): any;
@@ -209,3 +210,21 @@ function extractTsConfig(tsconfigPath: string, previousCompilerOptions?: Record<
   }
   return updatedCompilerOptions;
 }
+
+/**
+ * Detect if a given Node.js runtime uses SDKv2
+ */
+export function isSdkV2Runtime(runtime: Runtime): boolean {
+  const sdkV2RuntimeList = [
+    Runtime.NODEJS,
+    Runtime.NODEJS_4_3,
+    Runtime.NODEJS_6_10,
+    Runtime.NODEJS_8_10,
+    Runtime.NODEJS_10_X,
+    Runtime.NODEJS_12_X,
+    Runtime.NODEJS_14_X,
+    Runtime.NODEJS_16_X,
+  ];
+
+  return sdkV2RuntimeList.some((r) => {return r.family === runtime.family && r.name === runtime.name;});
+}

packages/aws-cdk-lib/aws-lambda-nodejs/test/function.test.ts

@@ -1,5 +1,5 @@
 import { bockfs } from '@aws-cdk/cdk-build-tools';
-import { Template, Match } from '../../assertions';
+import { Annotations, Template, Match } from '../../assertions';
 import { Vpc } from '../../aws-ec2';
 import { CodeConfig, Runtime } from '../../aws-lambda';
 import { App, Stack } from '../../core';
@@ -303,19 +303,69 @@ test('defaults to NODEJS_16_X with feature flag disabled', () => {
   });
 });
 
-test('defaults to NODEJS_LATEST with feature flag enabled', () => {
-  // GIVEN
-  const appLocal = new App({
-    context: {
-      [LAMBDA_NODEJS_USE_LATEST_RUNTIME]: true,
-    },
+describe('Node 18+ runtimes', () => {
+  test('defaults to NODEJS_LATEST with feature flag enabled', () => {
+    // GIVEN
+    const appFF = new App({
+      context: {
+        [LAMBDA_NODEJS_USE_LATEST_RUNTIME]: true,
+      },
+    });
+
+    const stackFF = new Stack(appFF, 'TestStackFF');
+
+    // WHEN
+    new NodejsFunction(stackFF, 'handler1');
+
+    Template.fromStack(stackFF).hasResourceProperties('AWS::Lambda::Function', {
+      Runtime: 'nodejs18.x',
+    });
   });
-  const stackLocal = new Stack(appLocal, 'TestStackFF');
 
-  // WHEN
-  new NodejsFunction(stackLocal, 'handler1');
+  test('connection reuse for aws sdk v2 not set by default', () => {
+    // WHEN
+    new NodejsFunction(stack, 'handler1', {
+      runtime: Runtime.NODEJS_18_X,
+    });
 
-  Template.fromStack(stackLocal).hasResourceProperties('AWS::Lambda::Function', {
-    Runtime: 'nodejs18.x',
+    // THEN
+    Template.fromStack(stack).hasResourceProperties('AWS::Lambda::Function', {
+      Environment: Match.absent(),
+    });
+  });
+
+  test('connection reuse for aws sdk v2 can be explicitly not set', () => {
+    // WHEN
+    new NodejsFunction(stack, 'handler1', {
+      runtime: Runtime.NODEJS_18_X,
+      awsSdkConnectionReuse: false,
+    });
+
+    // THEN
+    Template.fromStack(stack).hasResourceProperties('AWS::Lambda::Function', {
+      Environment: Match.absent(),
+    });
+  });
+
+  test('setting connection reuse for aws sdk v2 has warning', () => {
+    // WHEN
+    new NodejsFunction(stack, 'handler1', {
+      runtime: Runtime.NODEJS_18_X,
+      awsSdkConnectionReuse: true,
+    });
+
+    // THEN
+    Annotations.fromStack(stack).hasWarning('*',
+      'The AWS_NODEJS_CONNECTION_REUSE_ENABLED environment variable does not exist in SDK v3. You have explicitly set `awsSdkConnectionReuse`; please make sure this is intentional. [ack: aws-cdk-lib/aws-lambda-nodejs:unusedSdkEvironmentVariable]',
+    );
+    // AND
+    Template.fromStack(stack).hasResourceProperties('AWS::Lambda::Function', {
+      Environment: {
+        Variables: {
+          AWS_NODEJS_CONNECTION_REUSE_ENABLED: '1',
+        },
+      },
+    });
   });
 });
+