propan 0.0.8.7

Propan framework: the simplest way to work with a messaging queues

Propan

Propan is a modern framework for building Applications based on Messaging Architecture.

The key features are:

• Easy: Designed to be easy to use and learn.
• Intuitive: Great editor support. Autocompletion everywhere.
• Dependencies management: Minimize code duplication. Multiple features from each argument and parameter declaration.
• Integrations: Propan is ready to using in pair with any http framework you want
• MQ independent: Single interface to popular MQ:
  • NATS (based on nats-py)
  • RabbitMQ (based on aio-pika)
• Greate to develop: cli tool provides great development expireince:
  • framework-independent way to rule application environment
  • application code hot reloading

---

Quickstart

Install using pip:

$ pip install "propan[async_rabbit]"
# or
$ pip install "propan[async_nats]"

Basic usage

Create an application with the following code at serve.py:

from propan import PropanApp
from propan.brokers.rabbit import RabbitBroker
# from propan.brokers.nats import NatsBroker

broker = RabbitBroker("amqp://guest:guest@localhost:5672/")
# broker = NatsBroker("nats://localhost:4222")

app = PropanApp(broker)

@broker.handle("test")
async def base_handler(body):
    '''Handle all default exchange messages with `test` routing key'''
    print(body)

And just run it:

$ propan run serve:app

---

Type casting

Propan uses pydantic to cast incoming function arguments to type according their type annotation.

from pydantic import BaseModel
from propan import PropanApp, Context
from propan.brokers.rabbit import RabbitBroker

broker = RabbitBroker("amqp://guest:guest@localhost:5672/")
app = PropanApp(broker)

class SimpleMessage(BaseModel):
    key: int

@broker.handle("test2")
async def second_handler(body: SimpleMessage):
    assert isinstance(body.key, int)

---

Dependencies

Propan has dependencies management policy close to pytest fixtures. You can specify in functions arguments which dependencies you would to use. Framework passes them from the global Context object.

Default context fields are: app, broker, context (itself), logger and message. If you call not existed field it returns None value.

But you can specify your own dependencies, call dependencies functions (like Fastapi Depends) and more.

from logging import Logger

import aio_pika
from propan import PropanApp, Context
from propan.brokers.rabbit import RabbitBroker

rabbit_broker = RabbitBroker("amqp://guest:guest@localhost:5672/")

app = PropanApp(rabbit_broker)

@rabbit_broker.handle("test")
async def base_handler(body: dict,
                       app: PropanApp,
                       broker: RabbitBroker,
                       context: Context,
                       logger: Logger,
                       message: aio_pika.Message,
                       not_existed_field):
    assert broker is rabbit_broker
    assert not_existed_field is None

---

CLI power

Propan has own cli tool providing following features:

• project generation
• multiprocessing workers
• project hot reloading
• custom context arguments passing

Context passing

For example: pass your current .env project setting to context

$ propan run serve:app --env=.env.dev

from propan import PropanApp, Context
from propan.brokers.rabbit import RabbitBroker
from pydantic import BaseSettings

broker = RabbitBroker("amqp://guest:guest@localhost:5672/")

app = PropanApp(broker)

class Settings(BaseSettings):
    ...

@app.on_startup
async def setup(env: str, context: Context):
    settings = Settings(_env_file=env)
    context.set_context("settings", settings)

Project template

Also propan cli is able to generate production-ready application template:

$ propan create [projectname]

Notice: project template require pydantic[dotenv] installation.

Run created project:

# Run rabbimq first
$ docker compose --file [projectname]/docker-compose.yaml up -d

# Run project
$ propan run [projectname].app.serve:app --env=.env --reload

Now you can enjoy a new development experience!

---

HTTP Frameworks integrations

You can use Propan MQBrokers without PropanApp. Just start and stop them according your application lifespan.

from fastapi import FastAPI
from propan.brokers.rabbit import RabbitBroker

broker = RabbitBroker("amqp://guest:guest@localhost:5672/")

app = FastAPI()

@broker.handle("test")
async def base_handler(body):
    print(body)

@app.on_event("startup")
async def start_broker():
    await broker.start()

@app.on_event("shutdown")
async def stop_broker():
    await broker.close()

Examples

To see more framework usages go to examples/