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.
- 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
Install the Functions Framework via pip:
pip install functions-frameworkOr, for deployment, add the Functions Framework to your requirements.txt file:
functions-framework==2.3.0
Create an main.py file with the following contents:
def hello(request):
return "Hello world!"Your function is passed a single parameter,
(request), which is a FlaskRequestobject.
Run the following command:
functions-framework --target=helloOpen http://localhost:8080/ in your browser and see Hello world!.
Create a main.py file with the following contents:
def hello(request):
return "Hello world!"Now install the Functions Framework:
pip install functions-frameworkUse the functions-framework command to start the built-in local development server:
functions-framework --target hello --debug
* 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: on
* Running on http://0.0.0.0:8080/ (Press CTRL+C to quit)(You can also use functions-framework-python if you potentially have multiple
language frameworks installed).
Send requests to this function using curl from another terminal window:
curl localhost:8080
# Output: Hello world!Create an main.py file with the following contents:
import functions_framework
@functions_framework.cloud_event
def hello_cloud_event(cloud_event):
return f"Received event with ID: {cloud_event['id']} and data {cloud_event.data}"
@functions_framework.http
def hello_http(request):
return "Hello world!"Run the following command to run hello_http target locally:
functions-framework --target=hello_httpOpen http://localhost:8080/ in your browser and see Hello world!.
Run the following command to run hello_cloud_event target locally:
functions-framework --target=hello_cloud_eventMore info on sending CloudEvents payloads, see examples/cloud_run_cloud_events instruction.
The framework includes an error handler that is similar to the
flask.Flask.errorhandler
function, which allows you to handle specific error types with a decorator:
import functions_framework
@functions_framework.errorhandler(ZeroDivisionError)
def handle_zero_division(e):
return "I'm a teapot", 418
def function(request):
1 / 0
return "Success", 200This function will catch the ZeroDivisionError and return a different
response instead.
-
Create a
main.pyfile with the following contents:def hello(event, context): print("Received", context.event_id)
-
Start the Functions Framework on port 8080:
functions-framework --target=hello --signature-type=event --debug --port=8080
-
In a second terminal, start the Pub/Sub emulator on port 8085.
export PUBSUB_PROJECT_ID=my-project gcloud beta emulators pubsub start \ --project=$PUBSUB_PROJECT_ID \ --host-port=localhost:8085
You should see the following after the Pub/Sub emulator has started successfully:
[pubsub] INFO: Server started, listening on 8085 -
In a third terminal, create a Pub/Sub topic and attach a push subscription to the topic, using
http://localhost:8080as its push endpoint. Publish some messages to the topic. Observe your function getting triggered by the Pub/Sub messages.export PUBSUB_PROJECT_ID=my-project export TOPIC_ID=my-topic export PUSH_SUBSCRIPTION_ID=my-subscription $(gcloud beta emulators pubsub env-init) git clone https://github.com/googleapis/python-pubsub.git cd python-pubsub/samples/snippets/ pip install -r requirements.txt python publisher.py $PUBSUB_PROJECT_ID create $TOPIC_ID python subscriber.py $PUBSUB_PROJECT_ID create-push $TOPIC_ID $PUSH_SUBSCRIPTION_ID http://localhost:8080 python publisher.py $PUBSUB_PROJECT_ID publish $TOPIC_ID
You should see the following after the commands have run successfully:
Created topic: projects/my-project/topics/my-topic topic: "projects/my-project/topics/my-topic" push_config { push_endpoint: "http://localhost:8080" } ack_deadline_seconds: 10 message_retention_duration { seconds: 604800 } . Endpoint for subscription is: http://localhost:8080 1 2 3 4 5 6 7 8 9 Published messages to projects/my-project/topics/my-topic.And in the terminal where the Functions Framework is running:
* 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: on * Running on http://0.0.0.0:8080/ (Press CTRL+C to quit) * Restarting with fsevents reloader * Debugger is active! * Debugger PIN: 911-794-046 Received 1 127.0.0.1 - - [11/Aug/2021 14:42:22] "POST / HTTP/1.1" 200 - Received 2 127.0.0.1 - - [11/Aug/2021 14:42:22] "POST / HTTP/1.1" 200 - Received 5 127.0.0.1 - - [11/Aug/2021 14:42:22] "POST / HTTP/1.1" 200 - Received 6 127.0.0.1 - - [11/Aug/2021 14:42:22] "POST / HTTP/1.1" 200 - Received 7 127.0.0.1 - - [11/Aug/2021 14:42:22] "POST / HTTP/1.1" 200 - Received 8 127.0.0.1 - - [11/Aug/2021 14:42:22] "POST / HTTP/1.1" 200 - Received 9 127.0.0.1 - - [11/Aug/2021 14:42:39] "POST / HTTP/1.1" 200 - Received 3 127.0.0.1 - - [11/Aug/2021 14:42:39] "POST / HTTP/1.1" 200 - Received 4 127.0.0.1 - - [11/Aug/2021 14:42:39] "POST / HTTP/1.1" 200 -
For more details on extracting data from a Pub/Sub event, see https://cloud.google.com/functions/docs/tutorials/pubsub#functions_helloworld_pubsub_tutorial-python
-
Build a container from your function using the Functions buildpacks:
pack build \ --builder gcr.io/buildpacks/builder:v1 \ --env GOOGLE_FUNCTION_SIGNATURE_TYPE=http \ --env GOOGLE_FUNCTION_TARGET=hello \ my-first-function -
Start the built container:
docker run --rm -p 8080:8080 my-first-function # Output: Serving function... -
Send requests to this function using
curlfrom another terminal window:curl localhost:8080 # Output: Hello World!
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.
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). Here is an example Dockerfile that calls Functions Framework.
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).
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.
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 |
|---|---|---|
--host |
HOST |
The host on which the Functions Framework listens for requests. Default: 0.0.0.0 |
--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, event or cloudevent |
--source |
FUNCTION_SOURCE |
The path to the file containing your function. Default: main.py (in the current working directory) |
--debug |
DEBUG |
A flag that allows to run functions-framework to run in debug mode, including live reloading. Default: False |
--dry-run |
DRY_RUN |
A flag that allows for testing the function build from the configuration without creating a server. Default: False |
The Functions Framework can unmarshall incoming
Google Cloud Functions event payloads to event 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(event, context):
print(event)
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 will be used and automatic event unmarshalling will be disabled.
For more details on this signature type, see the Google Cloud Functions documentation on background functions.
See the running example.
The Functions framework can also unmarshall incoming CloudEvents payloads to the cloud_event object. This will be passed as a CloudEvent to your function when it receives a request. Note that your function must use the CloudEvents-style function signature:
def hello(cloud_event):
print(f"Received event with ID: {cloud_event['id']}")To enable automatic unmarshalling, set the function signature type to cloudevent 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.
More advanced guides can be found in the examples/ directory.
You can also find examples on using the CloudEvent Python SDK here.
Contributions to this library are welcome and encouraged. See CONTRIBUTING for more information on how to get started.