Panini is a python microframework based on the nats.py library. Its goal is to offer developers an easy way to create NATS microservices with a lower barrier of entry. It provides a specific template for creating microservices, similarly to FastAPI, Aiohttp, or Flask. Like all of the above frameworks, Panini has its design limits and edge cases. In the case that you become restricted by Panini's capabilities, we recommend switching to nats.py.
Panini was inspired by Faust project.
Documentation is here.
Before getting started make sure you have all the prerequisites installed:
pip install paniniA minimal app with one stream endpoint, one request endpoint, and one periodic task might look like this:
from panini import app as panini_app
app = panini_app.App(
service_name='listener_app',
host='127.0.0.1',
port=4222,
)
@app.listen("some.subject.for.request")
async def request_listener(msg):
""" request endpoint """
print(f"request {msg.data} from {msg.subject} has been processed")
return {"success": True, "message": "request has been processed"}
@app.listen("some.subject.for.stream")
async def stream_listener(msg):
""" stream endpoint """
print(f"event {msg.data} from {msg.subject} has been processed")
if __name__ == "__main__":
app.start()What's going on here?
- Imported Panini.
- Initialized app. Created an instance of class App from module panini with any microservice name, NATS host, and port.
- First
@app.listenregisters the listening subject"some.subject.for.request"withrequest_listener. Every time this app receives a request addressed to"some.subject.for.request", the functionrequest_listeneris called to process it, then it sends a return response back to an addressee. - Secondly
@app.listenregister the listening subject"some.subject.for.stream"withstream_listener. Same as withrequest_listenerbut without sending the result back. app.start()runs an app. No code under this command will ever be called.
Save the above code to file listener_app.py.
💡 The current function expects only JSON formattable returns, dict or list. However, you can also specify it as string or bytes. More details about this in Datatypes section._Make sure that you have all prerequisites from Install. Open the terminal to run the app:
> python3 listener_app.py
======================================================================================
Panini service connected to NATS..
id: 3
name: listener_app__non_docker_env_270377__75017
NATS brokers:
* nats://127.0.0.1:4222
======================================================================================That's it. Now let's create something that will generate messages.
Our goal here is to trigger endpoints from listener app above:
- "some.subject.for.request" - request something, receive response
- "some.subject.for.stream" - send some event without waiting for response
from panini import app as panini_app
app = panini_app.App(
service_name='sender_app',
host='127.0.0.1',
port=4222,
)
@app.task(interval=1)
async def request_periodically():
message = {"data":"request1234567890"}
response = await app.request(
subject="some.subject.for.request",
message=message,
)
print(response)
@app.task(interval=1)
async def publish_periodically():
message = {"data":"event1234567890"}
await app.publish(
subject="some.subject.for.stream",
message=message,
)
if __name__ == "__main__":
app.start()What's new here:
- First,
@app.taskregisters functionrequest_periodicallyto call it periodically at given interval, each 1 second in the example. - Function
app.requestsends requests, asynchronously waits for a response. - The second
@app.taskdoes the same as the first one but for publishing. - Function
app.publishsends a message like a request but without expecting any response. Fire and forget.
Save the code to new file sender_app.py.
Make sure that listener_app.py keeps running, then open a new terminal session to run the sender app:
> python3 sender_app.py
======================================================================================
Panini service connected to NATS..
id: 3
name: sender_app__non_docker_env_270377__75017
NATS brokers:
* nats://127.0.0.1:4222
======================================================================================
{'success': True, 'message': 'request has been processed'}
{'success': True, 'message': 'request has been processed'}
{'success': True, 'message': 'request has been processed'}
{'success': True, 'message': 'request has been processed'}
{'success': True, 'message': 'request has been processed'}
{'success': True, 'message': 'request has been processed'}
{'success': True, 'message': 'request has been processed'}
{'success': True, 'message': 'request has been processed'}Note that in the terminal session where you run listener_app.py you should see received requests and events:
event {'data': 'event1234567890'} from some.subject.for.stream has been processed
request {'data': 'request1234567890'} from some.subject.for.request has been processed
event {'data': 'event1234567890'} from some.subject.for.stream has been processed
request {'data': 'request1234567890'} from some.subject.for.request has been processed
event {'data': 'event1234567890'} from some.subject.for.stream has been processed
request {'data': 'request1234567890'} from some.subject.for.request has been processed
event {'data': 'event1234567890'} from some.subject.for.stream has been processed
request {'data': 'request1234567890'} from some.subject.for.request has been processed
event {'data': 'event1234567890'} from some.subject.for.stream has been processed
request {'data': 'request1234567890'} from some.subject.for.request has been processed
event {'data': 'event1234567890'} from some.subject.for.stream has been processed
request {'data': 'request1234567890'} from some.subject.for.request has been processedIn the first example, we created an application that listens for messages, in the second example, an application that sends messages. Panini allows you to freely combine sending and receiving messages in one application.
Let's check out what else you can do with Panini using a minimal interface:
- One-time tasks on start. Similar to the above periodic task but without
intervalargument
@app.task()
async def publish():
while True:
message = get_some_update()
await app.publish(subject='some.subject', message=message)- Synchronous endpoints
@app.task(interval=2)
def your_periodic_task():
for _ in range(10):
app.publish_sync(
subject='some.publish.subject',
message={'some':'data'}
)- Accept different datatypes: dict, str, bytes
@app.timer_task(interval=2)
def your_periodic_task():
for _ in range(10):
app.publish_sync(
subject='some.publish.subject',
message=b'messageinbytestosend',
data_type=bytes
)- Create middlewares for NATS messages
from panini.middleware import Middleware
class MyMiddleware(Middleware):
async def send_publish(self, subject, message, publish_func, **kwargs):
print('do something before publish')
await publish_func(subject, message, **kwargs)
print('do something after publish')
async def listen_publish(self, msg, cb):
print('do something before listen')
await cb(msg)
print('do something after listen')
async def send_request(self, subject, message, request_func, **kwargs):
print('do something before send request')
result = await request_func(subject, message, **kwargs)
print('do something after send request')
return result
async def listen_request(self, msg, cb):
print('do something before listen request')
result = await cb(msg)
print('do something after listen request')
return result-
Create HTTP endpoints with Aiohttp and NATS endpoints all together in one microservice
from aiohttp import web @app.listen('some.publish.subject') async def subject_for_requests_listener(msg): handle_incoming_message(msg.subject, msg.data) @app.http.get('/get') async def web_endpoint_listener(request): """ Single HTTP endpoint """ return web.Response(text="Hello, world") @app.http.view('/path/to/rest/endpoints') class MyView(web.View): """ HTTP endpoints for REST schema """ async def get(self): request = self.request return web.Response(text="Hello, REST world") async def post(self): request = self.request return web.Response(text="Hello, REST world")
-
Built-in traffic balancing between instances of the microservice if you have high loads
app = panini_app.App(
service_name='async_publish',
host='127.0.0.1',
allocation_queue_group='group24',
port=4222,
)
# incoming traffic will be distributed among
# all microservices that are in the "group24"Need more examples? Check here.
We use pytest for testing
To run tests (notice, that nats-server must be running on port 4222 for tests):
pytestWelcome contributor! We are looking developers to make Panini a great project.
Working on your first Pull Request? You can learn how from this free series, How to Contribute to an Open Source Project on GitHub.
Here's how you can help:
- suggest new updates or report about bug here
- review a pull request
- fix an issue
- write a tutorial
- always follow by this guide for your contributions
At this point, you're ready to make your changes! Feel free to ask for help 😸
![dependabot[bot] avatar](https://avatars.githubusercontent.com/in/29110?v=4 "dependabot[bot]")
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