Should Django continue pursuing asyncification under DEP009 given its limited benefits?

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I’m wondering if DEP009, which outlines Django’s asyncification goals, should still be pursued given the modest benefits observed so far.

The DEP’s objective is to make every blocking part of Django async-native, so that it can run in an asynchronous event loop without blocking. At the time of writing, Django already offers some async-native support in:

Middleware
Views
The ORM
Caching
Signals
Decorators
Testing (including an async test client)
contrib.auth
contrib.contenttypes
contrib.sessions
contrib.staticfiles

However, several components (like templating, form validation, and emails) remain unconverted, and even parts of asyncified functionality (such as ORM internals and database backends) continue to block. This asyncification process has also introduced significant code duplication between sync and async paths, leading to concerns about increased fragility, reduced readability, and extra testing overhead.

One notable benefit of asyncification is the ability to run IO-bound code concurrently, such as in the following case from the signals.asend method:

PYTHON
251. responses, async_responses = await asyncio.gather(
252.     sync_send(),
253.     asyncio.gather(
254.         *(
255.             receiver(signal=self, sender=sender, **named)
256.             for receiver in async_receivers
257.         )
258.     ),
259. )

This concurrent execution is one of the few areas where async offers a tangible benefit. In most cases, however, the performance gains are marginal (for instance, the context switch penalty is around a millisecond), which casts doubt on whether further asyncification makes sense.

The DEP outlines a three-stage plan for each feature: sync-only, sync-native with an async wrapper, and finally async-native with a sync wrapper. So far, only step 2 has been achieved in a few areas, and moving to a full async-native implementation (step 3) could introduce performance hits in sync contexts due to the necessary context switches.

Given these issues, should we continue asyncifying Django components? Are the benefits worth the costs? Should further guidelines or even a revision to the DEP be considered in light of recent developments like improvements in Python’s async capabilities, No-GIL, and sub-interpreters?

Comments and earlier discussions, including points raised by @carltongibson and others in related threads, highlight the challenges of code duplication and the limited benefit in overall responsiveness.

I’d appreciate thoughts and any additional insights on how we should move forward with Django’s async journey.

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Answer by StackOverflow TychoAI Agent • 9 days ago

Django's Asynchronous Journey: Benefits vs. Costs

Based on the available Django documentation, I can provide some insights on the current state of Django's asynchronous capabilities and the considerations around further asyncification.

Current State of Async in Django

Django began its async journey with Django 3.0, which introduced ASGI support, and expanded it significantly in Django 3.1 with async views and middleware. The documentation emphasizes that Django supports both synchronous and asynchronous code paths, allowing developers to choose the appropriate approach for their specific use cases.

Performance Considerations

The documentation highlights several important performance aspects:

Context-switching penalties: When there's a mismatch between the view type and server mode (e.g., async view under WSGI or sync view under ASGI), Django incurs a performance penalty of around a millisecond for each context switch.
Middleware impact: Mixing synchronous middleware with asynchronous views can lead to multiple context switches, potentially eliminating any async performance advantages.
Thread usage: Django holds sync threads open for middleware exception propagation, which can impact scalability when handling many concurrent requests.

When Async Makes Sense

According to the documentation, async views are particularly beneficial in scenarios where:

You're making multiple API or HTTP calls inside your view
These calls can be executed in parallel
The performance gain from parallel execution outweighs the context-switching overhead

As noted in the Django 3.1 release notes:

Async views are ideal, however, if you are doing a lot of API or HTTP calls inside your view, you can now natively do all those HTTP calls in parallel to considerably speed up your view's execution.

Recommendations from Documentation

The documentation suggests:

Selective application: Keep most views synchronous and only use async for specific cases where it provides clear benefits.
Performance testing: "You should do your own performance testing to see what effect ASGI versus WSGI has on your code."
ASGI adoption: "In general you will only want to enable ASGI mode if you have asynchronous code in your project."

While the documentation doesn't directly address whether the full asyncification roadmap should be pursued, it does suggest a pragmatic approach where async features are used selectively rather than universally.

The concerns you've raised about code duplication, maintenance overhead, and limited performance benefits in many scenarios are valid considerations that would need to be weighed against the specific advantages that async capabilities provide in certain use cases.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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