AWS WSGI Adapter for Lambda/API Gateway

Common errors

• Unable to import module 'lambda_function': No module named 'awsgi'

  cause The `aws-wsgi` library or its dependencies are not correctly packaged or deployed within the Lambda environment, or the import path is incorrect.
  fix Ensure `aws-wsgi` is included in your Lambda deployment package (e.g., in a layer or directly in the zip file). When using `pip`, install to a specific target directory: `pip install aws-wsgi -t ./python` and then zip the `python` directory.

• 500 Internal Server Error: 'wsgi.input' is not available

  cause This generic WSGI error often indicates a malformed API Gateway event or an issue with how the adapter is attempting to read the request body, possibly due to unexpected content types or missing data.
  fix Verify the incoming API Gateway event structure matches the expected Lambda Proxy Integration format. Ensure clients are sending valid request bodies, especially for POST/PUT requests, and that appropriate `Content-Type` headers are set.

Warnings

• breaking The official `slank/awsgi` GitHub repository has been archived since March 13, 2024, and is now read-only. This indicates that the original project is no longer actively maintained.
  Fix: For new projects or continued maintenance, consider migrating to an actively maintained fork like `awsgi2` (`pip install awsgi2`) or an alternative serverless WSGI solution like `serverless-wsgi`.
• gotcha API Gateway requires proper `binaryMimeTypes` configuration to handle binary data (e.g., images, fonts). Without this, binary content might be base64 encoded and sent as text, leading to display issues in the client.
  Fix: Ensure that your API Gateway stages are configured with the correct `binaryMimeTypes` (e.g., `image/png`, `font/woff2`) and that your Lambda response correctly sets `isBase64Encoded` to true for binary content.
• gotcha AWS Lambda has a 6MB payload limit for requests. Directly uploading large files via API Gateway and Lambda will hit this limit.
  Fix: For file uploads exceeding 6MB, use AWS S3 pre-signed URLs to allow clients to directly upload files to S3, bypassing Lambda's payload limit.
• gotcha WSGI applications deployed to AWS Lambda require explicit IAM permissions for the Lambda execution role to interact with other AWS services (e.g., S3, DynamoDB).
  Fix: Verify that the IAM role associated with your Lambda function has all necessary permissions (e.g., `s3:GetObject`, `dynamodb:PutItem`) for any AWS services your application intends to access.

Install

• pip install aws-wsgi Install from PyPI

Imports

• awsgi

  import awsgi

  The primary interface is the 'awsgi' module itself, which contains the 'response' function.

Quickstart

This quickstart demonstrates how to integrate a simple Flask application with `aws-wsgi` to run on AWS Lambda via API Gateway. The `lambda_handler` function serves as the entry point for AWS Lambda, passing the event and context to `awsgi.response`.

import awsgi
from flask import Flask, jsonify, request

app = Flask(__name__)

@app.route('/')
def index():
    return jsonify({
        'message': 'Hello from aws-wsgi!',
        'path': request.path,
        'method': request.method
    })

def lambda_handler(event, context):
    return awsgi.response(app, event, context)

# To test locally (e.g., with 'python -m flask run')
if __name__ == '__main__':
    app.run(debug=True)