feat: Add ability to package LLRT as a layer

.projenrc.ts

@@ -42,6 +42,7 @@ const project = new awscdk.AwsCdkConstructLibrary({
   },
 });
 
+project.projectBuild.postCompileTask.exec('cp src/layer.Dockerfile lib/layer.Dockerfile');
 project.addPackageIgnore('.tmp');
 // required to run integ tests
 project.projectBuild.testTask.exec('npm ci', { cwd: join('example', 'lambda') });

README.md

@@ -24,7 +24,11 @@ If you are already using `NodejsFunction` construct, you should be able to just
 > [!WARNING]
 > LLRT is currently experimental and not fully compatible with Node.js. You should expect some trial and errors to use LLRT with your existing code.
 
-If you want to upgrade the LLRT version, remove the `.tmp` directory, which contains the cache of LLRT binary fetched from GitHub (only applicable when you set `llrtVersion` to `latest` (default)).
+### LLRT version
+
+By default the latest version of LLRT is fetched from GitHub (unless you set `llrtVersion`). This LLRT binary is cached, in a `.tmp` directory or inside a docker image if you set `useLambdaLayer`.
+
+If you want to upgrade the LLRT version you will need to remove the `.tmp` directory or remove the docker images (the images can be identified during the cdk build e.g. `docker.io/library/cdk-926fb3006b78cf5a5efe8e6485491147c08a50b8ada8272a6761a8ddc85b2aec:latest` and can be removed using `docker image rm <image>`).
 
 ### Setting platform=browser
 
@@ -84,5 +88,17 @@ const handler = new LlrtFunction(this, 'Handler', {
 });
 ```
 
+### LLRT Layer
+
+By default, CDK Lambda LLRT bundles the LLRT bootstrap binary directly in your lambda function.
+If you want to package the binary in a separate layer that can be shared amongst functions then set `llrtLayer` to `true`.
+
+```ts
+const handler = new LlrtFunction(this, 'Handler', {
+    entry: 'lambda/index.ts',
+    llrtLayer: true
+});
+```
+
 ## Examples
 See [example](./example/README.md) for examples to use `LlrtFunction` construct.

example/index.ts

@@ -98,6 +98,22 @@ class LlrtFunctionTestStack extends Stack {
       const resource = api.root.addResource('ssr');
       resource.addMethod('GET', new LambdaIntegration(handler));
     }
+
+    {
+      // multiple lambda functions using a shared layer
+      new Array(3).fill(0).map((_, i) => {
+        const handler = new LlrtFunction(this, `LayerHandler${i}`, {
+          entry: '../example/lambda/s3.ts',
+          useLambdaLayer: true,
+        });
+        handler.addToRolePolicy(
+          new PolicyStatement({
+            actions: ['s3:ListAllMyBuckets'],
+            resources: ['*'],
+          })
+        );
+      })
+    }
   }
 }
 

src/layer.Dockerfile

@@ -0,0 +1,8 @@
+# Used to build assets when useLambdaLayer is true. Downloads the LLRT runtime
+# specified by the URL argument and expands it to the /assets folder 
+FROM alpine
+
+ARG URL=https://github.com/awslabs/llrt/releases/latest/download/llrt-lambda-x64.zip
+
+RUN wget -O llrt_temp.zip ${URL} && \
+    unzip llrt_temp.zip -d /asset

src/llrt-function.ts

@@ -1,6 +1,6 @@
 import { posix } from 'path';
-import { CfnResource } from 'aws-cdk-lib';
-import { Architecture, Runtime, RuntimeFamily } from 'aws-cdk-lib/aws-lambda';
+import { CfnResource, Stack } from 'aws-cdk-lib';
+import { Architecture, Code, ILayerVersion, LayerVersion, Runtime, RuntimeFamily } from 'aws-cdk-lib/aws-lambda';
 import { ICommandHooks, NodejsFunction, NodejsFunctionProps, OutputFormat } from 'aws-cdk-lib/aws-lambda-nodejs';
 import { Construct } from 'constructs';
 
@@ -46,12 +46,26 @@ export interface LlrtFunctionProps extends NodejsFunctionProps {
    * @default - If this option is not provided, the LLRT binary is downloaded from GitHub and cached in the .tmp directory.
    */
   readonly llrtBinaryPath?: string;
+
+  /**
+   * If `true` then the LLRT runtime will be built in a layer that can be shared amongst
+   * other `LLrtFunction`s that utilize the same `llrtBinaryType`, `llrtVersion` and `architecture`.
+   * 
+   * This feature cannot be used with `llrtBinaryPath` and if both are set a ValidationError will be thrown.
+   * 
+   * @default - false
+   */
+  readonly useLambdaLayer?: boolean;
 }
 
 export class LlrtFunction extends NodejsFunction {
   constructor(scope: Construct, id: string, props: LlrtFunctionProps) {
+    if (props.useLambdaLayer && props.llrtBinaryPath) {
+      throw new Error("useLambdaLayer not supported with llrtBinaryPath");
+    }
+
     const version = props.llrtVersion ?? 'latest';
-    const arch = props.architecture == Architecture.ARM_64 ? 'arm64' : 'x64';
+    const arch = props.architecture?.name == Architecture.ARM_64.name ? 'arm64' : 'x64';
     const binaryType = props.llrtBinaryType ?? LlrtBinaryType.STANDARD;
 
     let binaryName: string;
@@ -117,18 +131,26 @@ export class LlrtFunction extends NodejsFunction {
     const cacheDir = `.tmp/llrt/${version}/${arch}/${binaryType}`;
 
     const { commandHooks: originalCommandHooks, ...otherBundlingProps } = props.bundling ?? {};
-    const afterBundlingCommandHook: ICommandHooks['afterBundling'] = (i, o) => !props.llrtBinaryPath ? [
+    const afterBundlingCommandHook: ICommandHooks['afterBundling'] = (i, o) => {
+      // If useLambdaLayer then we'll package the llrt binary with docker later
+      if (props.useLambdaLayer) return [];
+      // Copy llrt binary from llrtBinaryPath
+      if (props.llrtBinaryPath) return [
+        `cp ${posix.join(i, props.llrtBinaryPath)} ${posix.join(o, 'bootstrap')}`,
+      ];
       // Download llrt binary from GitHub release and cache it
-      `if [ ! -e ${posix.join(i, cacheDir, 'bootstrap')} ]; then
-        mkdir -p ${posix.join(i, cacheDir)}
-        cd ${posix.join(i, cacheDir)}
-        curl -L -o llrt_temp.zip ${binaryUrl}
-        unzip llrt_temp.zip
-        rm -rf llrt_temp.zip
-        cd -
-       fi`,
-      `cp ${posix.join(i, cacheDir, 'bootstrap')} ${o}`,
-    ] : [`cp ${posix.join(i, props.llrtBinaryPath)} ${posix.join(o, 'bootstrap')}`];
+      return [
+        `if [ ! -e ${posix.join(i, cacheDir, 'bootstrap')} ]; then
+          mkdir -p ${posix.join(i, cacheDir)}
+          cd ${posix.join(i, cacheDir)}
+          curl -L -o llrt_temp.zip ${binaryUrl}
+          unzip llrt_temp.zip
+          rm -rf llrt_temp.zip
+          cd -
+        fi`,
+        `cp ${posix.join(i, cacheDir, 'bootstrap')} ${o}`,
+      ];
+    }
 
     super(scope, id, {
       // set this to remove an unnecessary environment variable.
@@ -154,6 +176,32 @@ export class LlrtFunction extends NodejsFunction {
       },
     });
 
+    if (props.useLambdaLayer) {
+      this.ensureLayer(binaryUrl, binaryName, version);
+    }
+
     (this.node.defaultChild as CfnResource).addPropertyOverride('Runtime', 'provided.al2023');
   }
+
+  private ensureLayer(binaryUrl: string, binaryName: string, version: string) {
+    const id = `${binaryName.replace("lambda", "layer")}-${version}`;
+
+    let layer = Stack.of(this).node.tryFindChild(id) as ILayerVersion;
+
+    if (!layer) {
+      layer = new LayerVersion(Stack.of(this), id, {
+        code: Code.fromDockerBuild(__dirname, {
+          buildArgs: {
+            URL: binaryUrl,
+          },
+          file: "layer.Dockerfile",
+        }),
+        compatibleArchitectures: [
+          this.architecture,
+        ],
+      });
+    }
+
+    this.addLayers(layer);
+  }
 }

test/integ.llrt-function.js.snapshot/LlrtFunctionIntegTestDefaultTestDeployAssertF3D2B976.assets.json

@@ -14,16 +14,16 @@
         }
       }
     },
-    "286c6bf5a2eda8d84fa67fd1004371db925b13e33838d7fc46026ffaad295c90": {
+    "5ab45ed51a21459ad67b9118a974fd3fbff643528f51f4fefc0ea1d472a8ec23": {
       "displayName": "LlrtFunctionIntegTestDefaultTestDeployAssertF3D2B976 Template",
       "source": {
         "path": "LlrtFunctionIntegTestDefaultTestDeployAssertF3D2B976.template.json",
         "packaging": "file"
       },
       "destinations": {
-        "current_account-current_region-734aaede": {
+        "current_account-current_region-d4e8dd96": {
           "bucketName": "cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}",
-          "objectKey": "286c6bf5a2eda8d84fa67fd1004371db925b13e33838d7fc46026ffaad295c90.json",
+          "objectKey": "5ab45ed51a21459ad67b9118a974fd3fbff643528f51f4fefc0ea1d472a8ec23.json",
           "assumeRoleArn": "arn:${AWS::Partition}:iam::${AWS::AccountId}:role/cdk-hnb659fds-file-publishing-role-${AWS::AccountId}-${AWS::Region}"
         }
       }