feat(lambda-nodejs): connection reuse with aws-sdk

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

@@ -41,6 +41,9 @@ new lambda.NodejsFunction(this, 'MyFunction', {
 
 All other properties of `lambda.Function` are supported, see also the [AWS Lambda construct library](https://github.com/aws/aws-cdk/tree/master/packages/%40aws-cdk/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.
+
 Use the `containerEnvironment` prop to pass environments variables to the Docker container
 running Parcel:
 

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

@@ -1,7 +1,7 @@
-import * as lambda from '@aws-cdk/aws-lambda';
-import * as cdk from '@aws-cdk/core';
 import * as fs from 'fs';
 import * as path from 'path';
+import * as lambda from '@aws-cdk/aws-lambda';
+import * as cdk from '@aws-cdk/core';
 import { Bundling, ParcelBaseOptions } from './bundling';
 import { PackageJsonManager } from './package-json-manager';
 import { nodeMajorVersion, parseStackTrace } from './util';
@@ -35,6 +35,19 @@ export interface NodejsFunctionProps extends lambda.FunctionOptions, ParcelBaseO
    * `NODEJS_10_X` otherwise.
    */
   readonly runtime?: lambda.Runtime;
+
+  /**
+   * Whether to automatically reuse TCP connections when working with the AWS
+   * SDK for JavaScript.
+   *
+   * 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
+   */
+  readonly awsSdkConnectionReuse?: boolean;
 }
 
 /**
@@ -69,6 +82,11 @@ export class NodejsFunction extends lambda.Function {
         }),
         handler: `index.${handler}`,
       });
+
+      // Enable connection reuse for aws-sdk
+      if (props.awsSdkConnectionReuse ?? true) {
+        this.addEnvironment('AWS_NODEJS_CONNECTION_REUSE_ENABLED', '1');
+      }
     } finally {
       // We can only restore after the code has been bound to the function
       packageJsonManager.restore();

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

@@ -1,8 +1,9 @@
 import '@aws-cdk/assert/jest';
-import { Runtime } from '@aws-cdk/aws-lambda';
-import { Stack } from '@aws-cdk/core';
 import * as fs from 'fs';
 import * as path from 'path';
+import { ABSENT } from '@aws-cdk/assert';
+import { Runtime } from '@aws-cdk/aws-lambda';
+import { Stack } from '@aws-cdk/core';
 import { NodejsFunction } from '../lib';
 import { Bundling } from '../lib/bundling';
 
@@ -107,3 +108,27 @@ test('resolves entry to an absolute path', () => {
     entry: expect.stringMatching(/@aws-cdk\/aws-lambda-nodejs\/lib\/index.ts$/),
   }));
 });
+
+test('configures connection reuse for aws sdk', () => {
+  // WHEN
+  new NodejsFunction(stack, 'handler1');
+
+  expect(stack).toHaveResource('AWS::Lambda::Function', {
+    Environment: {
+      Variables: {
+        AWS_NODEJS_CONNECTION_REUSE_ENABLED: '1',
+      },
+    },
+  });
+});
+
+test('can opt-out of connection reuse for aws sdk', () => {
+  // WHEN
+  new NodejsFunction(stack, 'handler1', {
+    awsSdkConnectionReuse: false,
+  });
+
+  expect(stack).toHaveResource('AWS::Lambda::Function', {
+    Environment: ABSENT,
+  });
+});

packages/@aws-cdk/aws-lambda-nodejs/test/integ.dependencies.expected.json

@@ -79,7 +79,12 @@
             "Arn"
           ]
         },
-        "Runtime": "nodejs12.x"
+        "Runtime": "nodejs12.x",
+        "Environment": {
+          "Variables": {
+            "AWS_NODEJS_CONNECTION_REUSE_ENABLED": "1"
+          }
+        }
       },
       "DependsOn": [
         "externalServiceRole85A00A90"

packages/@aws-cdk/aws-lambda-nodejs/test/integ.function.expected.json

@@ -79,7 +79,12 @@
             "Arn"
           ]
         },
-        "Runtime": "nodejs12.x"
+        "Runtime": "nodejs12.x",
+        "Environment": {
+          "Variables": {
+            "AWS_NODEJS_CONNECTION_REUSE_ENABLED": "1"
+          }
+        }
       },
       "DependsOn": [
         "tshandlerServiceRole8876B8E7"
@@ -164,7 +169,12 @@
             "Arn"
           ]
         },
-        "Runtime": "nodejs12.x"
+        "Runtime": "nodejs12.x",
+        "Environment": {
+          "Variables": {
+            "AWS_NODEJS_CONNECTION_REUSE_ENABLED": "1"
+          }
+        }
       },
       "DependsOn": [
         "jshandlerServiceRole781AF366"