Question
Answer and Explanation
When deploying an AWS Lambda function using the AWS CDK and a requirements.txt file, there are specific installation requirements to ensure that your function has all its dependencies.
Here's a breakdown of what you need:
1. AWS CDK Setup:
- Ensure you have the AWS CDK installed and configured on your local machine. This is necessary to define and deploy your infrastructure. This involves installing the AWS CDK CLI and having the necessary AWS credentials configured. For example, with npm you can install the CLI using: npm install -g aws-cdk.
2. Lambda Function Dependencies:
- Your Lambda function's dependencies must be listed in a requirements.txt file within your function's source code directory. This file specifies all the Python packages required by your function, for example: requests==2.25.1. This also applies to Python libraries.
3. Dependencies Packaging:
- Method 1: Bundling with CDK: The AWS CDK can automatically handle the packaging of your Lambda function's dependencies. When you define your Lambda function using the CDK, the CDK can use the requirements.txt file to bundle dependencies during deployment. This involves using the aws_lambda_python.PythonFunction construct in your CDK code.
- Method 2: Manual Layer Creation: If you have special requirements or need more control over the packaging, you can create a Lambda layer that includes the necessary packages. You'll then reference this layer in your Lambda function's definition within your CDK code. This can be useful for large dependencies or if you want to share packages across functions.
4. Correct Lambda Handler Path:
- Ensure the handler path specified in the CDK construct correctly matches the location of your handler function inside the code package. If your handler is in my_lambda_function.py, and the function is called handler, then the handler string should be my_lambda_function.handler.
5. Internet Access:
- If the function needs to access external resources, including downloading dependencies, you might need to configure your Lambda function to run inside a VPC (Virtual Private Cloud) with a NAT Gateway setup if your function is to access the internet using your own VPC. Otherwise, make sure the function has the necessary permissions to access the internet.
6. Correct Package Versions:
- It's highly important that versions of libraries in your `requirements.txt` are compatible with the Lambda execution environment. Lambda functions have particular environment settings and operating systems. Ensure that your packages in your requirements.txt are compatible with the Python version and system libraries available in the Lambda environment. Use explicit versions where possible to avoid unexpected changes during deployments.
7. CDK Dependency Installation:
- When using the CDK constructs that handle Lambda bundling automatically (like aws_lambda_python.PythonFunction), you must have certain packages installed on your machine to enable the bundling process. These packages are required by the CDK's bundling logic itself (e.g., Docker for containerized bundling).
In summary, to successfully deploy your Lambda function with dependencies using AWS CDK and a requirements.txt file:
- Have the AWS CDK installed and configured.
- Maintain a correct requirements.txt listing your function's dependencies.
- Use CDK methods to package your function's dependencies, either directly or through layers. Make sure that the dependencies you install are compatible with the Lambda environment.
- Verify the Lambda's execution role has the necessary permissions to access resources.