Deploy a Docker built Lambda function with AWS CDK

This project is a minimum working example of deploying an AWS Lambda function using Docker and AWS CDK.

Deploying Lambda functions using Docker has a number of benefits

• Package all necessary libraries into a single Docker image
• Bypass AWS Lambda's size constraint of 512 mb. Docker images stored on AWS ECR have a maximum size of 10 gb.
• Its easy!

GitHub Repository

CDK init & deploy

I wont cover setting up CDK and bootstrapping the environment. You can find that information here.

Once you have set up CDK, we need to set up the project:

1. mkdir cdk_docker_lambda && cd cdk_docker_lambda

2. cdk init --language python

3. source .venv/bin/activate

4. pip install -r requirements.txt && pip install -r requirements-dev.txt

   Now deploy empty stack to AWS:

5. cdk deploy

Stack design

Our stack will deploy only a lambda function. The lambda function will be built using Docker, so be sure to have Docker installed and the Docker daemon running.

# cdk_docker_lambda/cdk_docker_lambda_stack.pyfrom aws_cdk import Stackfrom aws_cdk import aws_lambda as _lambdafrom constructs import Constructclass CdkDockerLambdaStack(Stack):    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:        super().__init__(scope, construct_id, **kwargs)        self.build_lambda_func()    def build_lambda_func(self):        self.prediction_lambda = _lambda.DockerImageFunction(            scope=self,            id="ExampleDockerLambda",            # Function name on AWS            function_name="ExampleDockerLambda",            # Use aws_cdk.aws_lambda.DockerImageCode.from_image_asset to build            # a docker image on deployment            code=_lambda.DockerImageCode.from_image_asset(                # Directory relative to where you execute cdk deploy                # contains a Dockerfile with build instructions                directory="cdk_docker_lambda/ExampleDockerLambda"            ),        )

Lambda function

Create a new directory in cdk_docker_lambda called ExampleDockerLambda. Here we are going to put a Dockerfile, requirements.txt which holds our functions dependencies, and the lambda function itself, example_docker_lambda.py

cdk_docker_lambda/ExampleDockerLambda/Dockerfile

FROM amazon/aws-lambda-python:latestLABEL maintainer="Wesley Cheek"# Installs python, removes cache file to make things smallerRUN yum update -y && \    yum install -y python3 python3-dev python3-pip gcc && \    rm -Rf /var/cache/yum# Be sure to copy over the function itself!COPY example_docker_lambda.py ./# Copies requirements.txt file into the containerCOPY requirements.txt ./# Installs dependencies found in your requirements.txt fileRUN pip install -r requirements.txt# Points to the handler function of your lambda functionCMD ["example_docker_lambda.handler"]

cdk_docker_lambda/ExampleDockerLambda/requirements.txt

requests

cdk_docker_lambda/ExampleDockerLambda/example_docker_lambda.py

# Very simpleimport requestsdef handler(event, context):    return "Hello Lambda!"

Now cdk deploy. AWS CDK will build your new Lambda function using Docker and then push it for you to the ECR repository that was originally created for you by running cdk bootstrap during the CDK setup. How convenient.

After the image is built and pushed, CDK will deploy the necessary infrastructure. You can navigate to the AWS CloudFormation console to view the deployment. It should only take a couple minutes.

Once finished, you will find your beautiful Docker deployed Lambda function on the Lambda console

Test your Lambda function

We can use any kind of event since the function always just returns a string.

Have fun easily deploying any sized Lambda youd like using AWS CDK and Docker!