AWS Lambda Construct Library

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This construct library allows you to define AWS Lambda Functions.

import lambda = require('@aws-cdk/aws-lambda');
import path = require('path');

const fn = new lambda.Function(this, 'MyFunction', {
  runtime: lambda.Runtime.NODEJS_10_X,
  handler: 'index.handler',
  code: lambda.Code.fromAsset(path.join(__dirname, 'lambda-handler')),
});

Handler Code

The lambda.Code class includes static convenience methods for various types of runtime code.

• lambda.Code.fromBucket(bucket, key[, objectVersion]) - specify an S3 object that contains the archive of your runtime code.
• lambda.Code.fromInline(code) - inline the handle code as a string. This is limited to supported runtimes and the code cannot exceed 4KiB.
• lambda.Code.fromAsset(path) - specify a directory or a .zip file in the local filesystem which will be zipped and uploaded to S3 before deployment.

The following example shows how to define a Python function and deploy the code from the local directory my-lambda-handler to it:

Example of Lambda Code from Local Assets

When deploying a stack that contains this code, the directory will be zip archived and then uploaded to an S3 bucket, then the exact location of the S3 objects will be passed when the stack is deployed.

During synthesis, the CDK expects to find a directory on disk at the asset directory specified. Note that we are referencing the asset directory relatively to our CDK project directory. This is especially important when we want to share this construct through a library. Different programming languages will have different techniques for bundling resources into libraries.

Layers

The lambda.LayerVersion class can be used to define Lambda layers and manage granting permissions to other AWS accounts or organizations.

Example of Lambda Layer usage

Event Rule Target

You can use an AWS Lambda function as a target for an Amazon CloudWatch event rule:

import targets = require('@aws-cdk/aws-events-targets');
rule.addTarget(new targets.LambdaFunction(myFunction));

Event Sources

AWS Lambda supports a variety of event sources.

In most cases, it is possible to trigger a function as a result of an event by using one of the add<Event>Notification methods on the source construct. For example, the s3.Bucket construct has an onEvent method which can be used to trigger a Lambda when an event, such as PutObject occurs on an S3 bucket.

An alternative way to add event sources to a function is to use function.addEventSource(source). This method accepts an IEventSource object. The module @aws-cdk/aws-lambda-event-sources includes classes for the various event sources supported by AWS Lambda.

For example, the following code adds an SQS queue as an event source for a function:

import { SqsEventSource } from '@aws-cdk/aws-lambda-event-sources';
fn.addEventSource(new SqsEventSource(queue));

The following code adds an S3 bucket notification as an event source:

import { S3EventSource } from '@aws-cdk/aws-lambda-event-sources';
fn.addEventSource(new S3EventSource(bucket, {
  events: [ s3.EventType.OBJECT_CREATED, s3.EventType.OBJECT_DELETED ],
  filters: [ { prefix: 'subdir/' } ] // optional
}));

See the documentation for the @aws-cdk/aws-lambda-event-sources module for more details.

Lambda with DLQ

A dead-letter queue can be automatically created for a Lambda function by setting the deadLetterQueueEnabled: true configuration.

import lambda = require('@aws-cdk/aws-lambda');

const fn = new lambda.Function(this, 'MyFunction', {
    runtime: lambda.Runtime.NODEJS_8_10,
    handler: 'index.handler',
    code: lambda.Code.fromInline('exports.handler = function(event, ctx, cb) { return cb(null, "hi"); }'),
    deadLetterQueueEnabled: true
});

It is also possible to provide a dead-letter queue instead of getting a new queue created:

import lambda = require('@aws-cdk/aws-lambda');
import sqs = require('@aws-cdk/aws-sqs');

const dlq = new sqs.Queue(this, 'DLQ');
const fn = new lambda.Function(this, 'MyFunction', {
    runtime: lambda.Runtime.NODEJS_8_10,
    handler: 'index.handler',
    code: lambda.Code.fromInline('exports.handler = function(event, ctx, cb) { return cb(null, "hi"); }'),
    deadLetterQueue: dlq
});

See the AWS documentation to learn more about AWS Lambdas and DLQs.

Lambda with X-Ray Tracing

import lambda = require('@aws-cdk/aws-lambda');

const fn = new lambda.Function(this, 'MyFunction', {
    runtime: lambda.Runtime.NODEJS_8_10,
    handler: 'index.handler',
    code: lambda.Code.fromInline('exports.handler = function(event, ctx, cb) { return cb(null, "hi"); }'),
    tracing: lambda.Tracing.ACTIVE
});

See the AWS documentation to learn more about AWS Lambda's X-Ray support.

Lambda with Reserved Concurrent Executions

import lambda = require('@aws-cdk/aws-lambda');

const fn = new lambda.Function(this, 'MyFunction', {
    runtime: lambda.Runtime.NODEJS_8_10,
    handler: 'index.handler',
    code: lambda.Code.fromInline('exports.handler = function(event, ctx, cb) { return cb(null, "hi"); }'),
    reservedConcurrentExecutions: 100
});

See the AWS documentation managing concurrency.