Add FastAPI Background Tasks example

README.md

@@ -167,6 +167,7 @@ The Lambda Web Adapter also supports all non-HTTP event triggers, such as SQS, S
 
 - [FastAPI](examples/fastapi)
 - [FastAPI in Zip](examples/fastapi-zip)
+- [FastAPI with Background Tasks](examples/fastapi-background-tasks)
 - [FastAPI with Response Streaming](examples/fastapi-response-streaming)
 - [FastAPI with Response Streaming in Zip](examples/fastapi-response-streaming-zip)
 - [Flask](examples/flask)

examples/fastapi-background-tasks/.gitignore

@@ -0,0 +1,244 @@
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examples/fastapi-background-tasks/README.md

@@ -0,0 +1,78 @@
+# FastAPI Background Task example
+
+A basic FastAPI application example. You can build and test it locally as a typical FastAPI application.
+
+Using AWS Lambda Web Adapter, You can package this web application into Docker image, push to ECR, and deploy to Lambda, ECS/EKS, or EC2.
+
+The application can be deployed in an AWS account using the [Serverless Application Model](https://github.com/awslabs/serverless-application-model). The `template.yaml` file in the root folder contains the application definition.
+
+The top level folder is a typical AWS SAM project. The `app` directory is a FastAPI application with a [Dockerfile](app/Dockerfile).
+
+```dockerfile
+FROM public.ecr.aws/docker/library/python:3.12-slim
+COPY --from=public.ecr.aws/awsguru/aws-lambda-adapter:0.8.1 /lambda-adapter /opt/extensions/lambda-adapter
+ENV PORT=8000
+WORKDIR /var/task
+COPY requirements.txt ./
+RUN python -m pip install -r requirements.txt
+COPY *.py ./
+CMD exec uvicorn --port=$PORT main:app
+```
+
+Line 2 copies lambda web adapter binary into /opt/extensions. This is the change to run the FastAPI application on Lambda.
+
+```dockerfile
+COPY --from=public.ecr.aws/awsguru/aws-lambda-adapter:0.8.1 /lambda-adapter /opt/extensions/lambda-adapter
+```
+
+## Pre-requisites
+
+The following tools should be installed and configured.
+* [AWS CLI](https://aws.amazon.com/cli/)
+* [SAM CLI](https://github.com/awslabs/aws-sam-cli)
+* [Python](https://www.python.org/)
+* [Docker](https://www.docker.com/products/docker-desktop)
+
+
+## Deploy to Lambda
+Navigate to the sample's folder and use the SAM CLI to build a container image
+```shell
+$ sam build
+```
+
+This command compiles the application and prepares a deployment package in the `.aws-sam` sub-directory.
+
+To deploy the application in your AWS account, you can use the SAM CLI's guided deployment process and follow the instructions on the screen
+
+```shell
+$ sam deploy --guided
+```
+Please take note of the container image name.
+Once the deployment is completed, the SAM CLI will print out the stack's outputs, including the new application URL. You can use `curl` or a web browser to make a call to the URL
+
+```shell
+...
+---------------------------------------------------------------------------------------------------------
+OutputKey-Description                        OutputValue
+---------------------------------------------------------------------------------------------------------
+FastAPIURL - URL for application            https://xxxxxxxxxx.execute-api.us-west-2.amazonaws.com/
+---------------------------------------------------------------------------------------------------------
+...
+
+$ curl https://xxxxxxxxxx.execute-api.us-west-2.amazonaws.com/
+```
+
+## Run the docker locally
+
+We can run the same docker image locally, so that we know it can be deployed to ECS Fargate and EKS EC2 without code changes.
+
+```shell
+$ docker run -d -p 8000:8000 {ECR Image}
+
+```
+
+Use curl to verify the docker container works.
+
+```shell
+$ curl localhost:8000/ 
+```

examples/fastapi-background-tasks/app/Dockerfile

@@ -0,0 +1,8 @@
+FROM public.ecr.aws/docker/library/python:3.12-slim
+COPY --from=public.ecr.aws/awsguru/aws-lambda-adapter:0.8.1 /lambda-adapter /opt/extensions/lambda-adapter
+ENV PORT=8000
+WORKDIR /var/task
+COPY requirements.txt ./
+RUN python -m pip install -r requirements.txt
+COPY *.py ./
+CMD exec uvicorn --port=$PORT main:app

examples/fastapi-background-tasks/app/background.py

@@ -0,0 +1,45 @@
+from threading import Thread
+from queue import Queue
+import json
+import os
+import requests
+
+
+class BackgroundTaskExtension(Thread):
+    def __init__(self):
+        super().__init__()
+        self.daemon = True
+        self.queue = Queue()
+        self.session = requests.Session()
+        self.start()
+
+    def run(self):
+        # start an internal extension
+        response = self.session.post(
+            url=f"http://{os.environ['AWS_LAMBDA_RUNTIME_API']}/2020-01-01/extension/register",
+            json={'events': ['INVOKE'],},
+            headers={'Lambda-Extension-Name': 'background-task-extension' }
+        )
+        extension_id = response.headers['Lambda-Extension-Identifier']
+        while True:
+            response = self.session.get(
+                url=f"http://{os.environ['AWS_LAMBDA_RUNTIME_API']}/2020-01-01/extension/event/next",
+                headers={'Lambda-Extension-Identifier': extension_id},
+                timeout=None
+            )
+            event = json.loads(response.text)
+            if event['eventType'] == 'INVOKE':
+                while True:
+                    message = self.queue.get()
+                    if message['type'] == 'TASK':
+                        task, args, kwargs = message['task']
+                        task(*args, **kwargs)
+                    if message['type'] == 'DONE':
+                        break
+
+    def add_task(self, background_task, *args, **kwargs):
+        self.queue.put( {"type": "TASK",
+                         "task": (background_task, args, kwargs)} )
+
+    def done(self):
+        self.queue.put( {"type": "DONE"} )