Flask.md

Step 1: Setup your Puff project

Follow the instructions on how to setup a new poetry project and install Puff:

• Using the CLI

Step 2: Add a Flask app

Install Flask to your your project:

poetry add flask

Add your flask application in a new file my_puff_project/flask.py

from flask import Flask

app = Flask(__name__)

@app.route("/")
def hello_world():
    return "<p>Hello, World!</p>"

Update puff.toml with the following lines

wsgi = "my_puff_project.flask.app"

Run the server:

poetry run puff serve

To use Puff in development mode, use puff-watch which is a wrapper around puff that will restart the process when files change in the directory.

poetry run puff-watch serve
# Spawn multiple processes on the same Port to simulate gunicorn workers
PUFF_REUSE_PORT=true poetry run puff-watch --num 2 serve

Step 3: Add GraphQL

Create a new file called my_puff_project/graphql.py

from typing import Optional, Iterable, Any
from dataclasses import dataclass
from puff.pubsub import global_pubsub as pubsub


@dataclass
class DbObject:
    was_input: int
    title: str
    

@dataclass
class Query:
    @classmethod
    def hello_world(cls, parents, context, /, my_input: int) -> tuple[list[DbObject], str, list[Any]]:
        # Return a Raw query for Puff to execute in Postgres.
        # The ellipsis is a placeholder allowing the Python type system to know which field type it should transform into.
        return ..., "SELECT $1::int as was_input, \'hi from pg\'::TEXT as title", [my_input]

    @classmethod
    def auth_token(cls, context, /) -> str:
        # All GraphQL queries have access to the Bearer token if set.
        return context.auth_token()
    
    @classmethod
    def new_connection_id(cls, context, /) -> str:
        # Get a new connection identifier for pubsub.
        return pubsub.new_connection_id()


@dataclass
class Mutation:
    @classmethod
    def send_message_to_channel(cls, context, /, connection_id: str, channel: str, message: str) -> bool:
        return pubsub.publish_as(connection_id, channel, message)


@dataclass
class MessageObject:
    message_text: str
    from_connection_id: str
    num_processed: int


@dataclass
class Subscription:
    @classmethod
    def read_messages_from_channel(cls, context, /, channel: str, connection_id: Optional[str] = None) -> Iterable[MessageObject]:
        if connection_id is not None:
            conn = pubsub.connection_with_id(connection_id)
        else:
            conn = pubsub.connection()
        conn.subscribe(channel)
        num_processed = 0
        while msg := conn.receive():
            from_connection_id = msg.from_connection_id
            # Filter out messages from yourself.
            if connection_id != from_connection_id:
                yield MessageObject(message_text=msg.text, from_connection_id=from_connection_id, num_processed=num_processed)
                num_processed += 1


@dataclass
class Schema:
    query: Query
    mutation: Mutation
    subscription: Subscription

Update puff.toml with the following lines

[[pubsub]]
enable = true

[[graphql]]
url = "/graphql/"
subscription_url = "/subscriptions/"
playground_url = "/playground/"
database = "default"

Run the server and go to http://localhost:7777/playground/

Step 4: Add Distributed Tasks

Update puff.toml with the following lines

[[task_queue]]
enable = true

Create a new file called my_puff_project/tasks.py

from puff.task_queue import task

@task
def my_task(payload):
    print(f"Inside `my_task` with payload: {payload}")
    return {"from_task": payload}

Change your Mutation class in graphql.py to call the function through the queue:

from puff.task_queue import global_task_queue as tq
from my_puff_project.tasks import my_task

...

@dataclass
class Mutation:
    @classmethod
    def send_message_to_channel(cls, context, /, connection_id: str, channel: str, message: str) -> bool:
        tq.add_task(my_task, {"auth_token": context.auth_token(), "connection_id": connection_id, "channel": channel, "message": message})
        return pubsub.publish_as(connection_id, channel, message)

Run a worker server by using wait_forever in another tab:

poetry run puff wait_forever

Now run the server. Going to http://localhost:7777/graphql/ calling the mutation will trigger tasks.

poetry run puff serve