Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Supported runtimes for durable functions

Durable functions are available for Node.js and Python runtimes. You can create durable functions using managed runtimes in the Lambda console or deploy them using container images for additional runtime version flexibility.

Lambda managed runtimes

The following managed runtimes support durable functions when you create functions in the Lambda console or using the Amazon CLI with the --durable-config '{"ExecutionTimeout": 3600, "RetentionPeriodInDays": 7}' parameter. For complete information about Lambda runtimes, see Lambda runtimes.

Node.js

Install the SDK in your Node.js project:

npm install @aws/durable-execution-sdk-js
      

The SDK supports JavaScript and TypeScript. For TypeScript projects, the SDK includes type definitions.

Python

Install the SDK in your Python project:

pip install aws-durable-execution-sdk-python
      

The Python SDK uses synchronous methods and doesn't require async/await.

Container images

You can use durable functions with container images to support additional runtime versions or custom runtime configurations. Container images let you use runtime versions not available as managed runtimes or customize your runtime environment.

To create a durable function using a container image:

Python container example

Create a Dockerfile for Python 3.11:

FROM public.ecr.aws/lambda/python:3.11

# Copy requirements file
COPY requirements.txt ${LAMBDA_TASK_ROOT}/

# Install dependencies including durable SDK
RUN pip install -r requirements.txt

# Copy function code
COPY lambda_function.py ${LAMBDA_TASK_ROOT}/

# Set the handler
CMD [ "lambda_function.handler" ]
      

Create a requirements.txt file:

aws-durable-execution-sdk-python
      

Build and push the image:

# Build the image
docker build -t my-durable-function .

# Tag for ECR
docker tag my-durable-function:latest 123456789012.dkr.ecr.us-east-1.amazonaws.com/my-durable-function:latest

# Push to ECR
docker push 123456789012.dkr.ecr.us-east-1.amazonaws.com/my-durable-function:latest
      

Create the function with durable execution enabled:

aws lambda create-function \
  --function-name myDurableFunction \
  --package-type Image \
  --code ImageUri=123456789012.dkr.ecr.us-east-1.amazonaws.com/my-durable-function:latest \
  --role arn:aws:iam::123456789012:role/lambda-execution-role \
  --durable-config '{"ExecutionTimeout": 3600, "RetentionPeriodInDays": 7}'
      

For more information about using container images with Lambda, see Creating Lambda container images in the Lambda Developer Guide.

Runtime considerations

SDK version management: Include the durable execution SDK in your deployment package or container image. This ensures your function uses a specific SDK version and isn't affected by runtime updates. Pin SDK versions in your package.json or requirements.txt to control when you upgrade.

Runtime updates: Amazon updates managed runtimes to include security patches and bug fixes. These updates may include new SDK versions. To avoid unexpected behavior, include the SDK in your deployment package and test thoroughly before deploying to production.

Container image size: Container images have a maximum uncompressed size of 10 GB. The durable execution SDK adds minimal size to your image. Optimize your container by using multi-stage builds and removing unnecessary dependencies.

Cold start performance: Container images may have longer cold start times than managed runtimes. The durable execution SDK has minimal impact on cold start performance. Use provisioned concurrency if cold start latency is critical for your application.