Functions Framework for Python

An open source FaaS (Function as a service) framework for writing portable Python functions -- brought to you by the Google Cloud Functions team.

The Functions Framework lets you write lightweight functions that run in many different environments, including:

Google Cloud Functions
Your local development machine
Cloud Run and Cloud Run for Anthos
Knative-based environments

The framework allows you to go from:

def hello(request):
    return "Hello world!"

To:

curl http://my-url
# Output: Hello world!

All without needing to worry about writing an HTTP server or complicated request handling logic.

Features

Spin up a local development server for quick testing
Invoke a function in response to a request
Automatically unmarshal events conforming to the CloudEvents spec
Portable between serverless platforms

Installation

Install the Functions Framework via pip:

pip install functions-framework

Or, for deployment, add the Functions Framework to your requirements.txt file:

functions-framework==1.0.0

Quickstart: Hello, World on your local machine

Create an main.py file with the following contents:

def hello(request):
    return "Hello world!"

Run the following command:

functions-framework --target=hello

Open http://localhost:8080/ in your browser and see Hello world!.

Quickstart: Set up a new project

Create a main.py file with the following contents:

def hello(request):
    return "Hello world!"

Now install the Functions Framework:

pip install functions-framework

Use the functions-framework command to start the built-in local development server:

functions-framework --target hello
 * Serving Flask app "hello" (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://0.0.0.0:8080/ (Press CTRL+C to quit)

Send requests to this function using curl from another terminal window:

curl localhost:8080
# Output: Hello world!

Run your function on serverless platforms

Google Cloud Functions

This Functions Framework is based on the Python Runtime on Google Cloud Functions.

On Cloud Functions, using the Functions Framework is not necessary: you don't need to add it to your requirements.txt file.

After you've written your function, you can simply deploy it from your local machine using the gcloud command-line tool. Check out the Cloud Functions quickstart.

Cloud Run/Cloud Run on GKE

Once you've written your function and added the Functions Framework to your requirements.txt file, all that's left is to create a container image. Check out the Cloud Run quickstart for Python to create a container image and deploy it to Cloud Run. You'll write a Dockerfile when you build your container. This Dockerfile allows you to specify exactly what goes into your container (including custom binaries, a specific operating system, and more).

If you want even more control over the environment, you can deploy your container image to Cloud Run on GKE. With Cloud Run on GKE, you can run your function on a GKE cluster, which gives you additional control over the environment (including use of GPU-based instances, longer timeouts and more).

Container environments based on Knative

Cloud Run and Cloud Run on GKE both implement the Knative Serving API. The Functions Framework is designed to be compatible with Knative environments. Just build and deploy your container to a Knative environment.

Configure the Functions Framework

You can configure the Functions Framework using command-line flags or environment variables. If you specify both, the environment variable will be ignored.

Command-line flag	Environment variable	Description
`--port`	`PORT`	The port on which the Functions Framework listens for requests. Default: `8080`
`--target`	`FUNCTION_TARGET`	The name of the exported function to be invoked in response to requests. Default: `function`
`--signature-type`	`FUNCTION_SIGNATURE_TYPE`	The signature used when writing your function. Controls unmarshalling rules and determines which arguments are used to invoke your function. Default: `http`; accepted values: `http` or `event`
`--source`	`FUNCTION_SOURCE`	The path to the file containing your function. Default: `main.py` (in the current working directory)

Enable CloudEvents

The Functions Framework can unmarshall incoming CloudEvents payloads to data and context objects. These will be passed as arguments to your function when it receives a request. Note that your function must use the event-style function signature:

def hello(data, context):
    print(data)
    print(context)

To enable automatic unmarshalling, set the function signature type to event using the --signature-type command-line flag or the FUNCTION_SIGNATURE_TYPE environment variable. By default, the HTTP signature type will be used and automatic event unmarshalling will be disabled.

For more details on this signature type, check out the Google Cloud Functions documentation on background functions.

Advanced Examples

More advanced guides can be found in the examples/ directory.

Contributing

Contributions to this library are welcome and encouraged. See CONTRIBUTING for more information on how to get started.