(KOR) Django-channels을 적용한 애드투페이퍼 출력 시스템

1. A2P Printing System
using Django-Channels
Sin-Woo Bang at Add2paper

2. Add2paper
- providing a free-printing service.
- used by 700k college students.
- In detail : www.add2paper.com

3. User flow
- A user login and try to print on PC.

4. User flow
- Then the user go to a printing machine,
- pay for printing and complete it.

5. It is easy

6. An architecture in detail

7. When a user try to print
Send spool files info
to EC2
Save spool files in local

8. Payment
Request a payment

9. Printing
Send a printing signal
via WebSocket

10. Printing
Deliver spool files

11. Summary
(1) Send a spool file info to a server
(2) Request a payment to the server
(3) When the server detect payment
completed, sends a printing signal
(4) PC delivers spool files to
a printing machine.

13. As you know in Python
- Famous web frameworks had not done support WebSocket.
- like Flask, Django.
- So we had to consider gevent, Twisted to use that.

14. But in 2016

16. Now Django/Channels in 2018
- Updated to 2.x version.
- Activated open source activities.
- A lot of pull requests are opened and merged now.
- Fine to use in production.

17. We chose it
- since our backend applications are written in Python.
- to send a printing signal when a payment is finished.

18. It was very easy
- Just add some settings if you want to add it.
- Settings for
- ASGI
- Channel-Layers (for using In-memory DB like Redis)
- Routing for asynchronous requests

19. Developed quickly

20. Write a business logic
- awesome productivity
- could take strength of Django as it is

21. But, when it comes to deployment

23. Deployment
- Daphne which is a protocol server for ASGI does not support graceful reload.
- had to use blue-green way by adjusting a load balancer.

24. Now
- The service works fine.
- Since it is scalable, our team could add additional servers.
- If you consider to use it
- Recommending
- if you should keep a deadline.
- if a project is not too much big.
- But
- Please remember Daphne does not support graceful reload.

25. Thank you
- Q&A : dev@add2paper.com or sinwoobang@gmail.com