About new container_context

[lesnik512]

@vrslev Raised some questions. @alexanderlazarev0 Let's discuss them, before releasing as 2.0.0

In new design default value of reset_all_containers is False in container_context, while in DIContextMiddleware it's True. Maybe make them consistent?

[alexanderlazarev0]

Agreed, if you notice anything else, please let me know. I will make those changes as part of the pull request for #140.

Also, @lesnik512 I have already migrated a larger application to the pre-release version and haven't had any issues. However, keep in mind that that app does not make use of the global_context.

[lesnik512]

@alexanderlazarev0

However, keep in mind that that app does make use of the global_context.

Do you mean, that it doesn't make use of the global_context?

[alexanderlazarev0]

See #143 (Work in progress)

[alexanderlazarev0]

Okay there is actually a large issue on the pre-release version 2.0.0a0 (alpha):

Here was my first example to reproduce:

# app.py
from that_depends import providers
from that_depends import BaseContainer, container_context, inject, Provide
import uvicorn

app = FastAPI()


async def async_creator() -> typing.Iterator[str]:
    try:
        await asyncio.sleep(1)
        yield str(uuid4())
    finally:
        print("Tearing down")


class MyContainer(BaseContainer):
    my_async_context_resource = providers.ContextResource(async_creator)

async def init_container_context():
    async with container_context(MyContainer):
        yield


router = APIRouter(dependencies=[Depends(init_container_context)])

@container_context()
@inject
async def injected(val: str = Provide[MyContainer.my_async_context_resource]) -> str:
    return val

@router.get("/")
async def read_root():
    return await injected()

app.include_router(router)

if __name__ == "__main__":
    uvicorn.run("test:app", port=8008, reload=True)

# stress_test.py
import threading
import requests

# Define the target endpoint and the payload
endpoint = "http://localhost:8008/"
# Function to send a single request
def send_request():
    try:
        response = requests.get(endpoint)
        print(f"Response Code: {response.status_code}, Response Body: {response.text}")
    except Exception as e:
        print(f"Request failed: {e}")
if __name__ == '__main__':

    # Create and start multiple threads
    num_threads = 50  # Number of simultaneous requests
    threads = []

    for _ in range(num_threads):
        thread = threading.Thread(target=send_request)
        threads.append(thread)
        thread.start()

    # Wait for all threads to finish
    for thread in threads:
        thread.join()

Long story short, this causes a contextvar issue because of context switching (asyncio). I already found the fix (I believe) so just writing this here in case someone else sees this.

[alexanderlazarev0]

Here is a test that reproduces this behaviour (already added in #143):

async def test_async_context_switching() -> None:
    async def slow_async_creator() -> typing.AsyncIterator[str]:
        await asyncio.sleep(0.1)
        yield str(uuid.uuid4())

    class MyContainer(BaseContainer):
        slow_provider = providers.ContextResource(slow_async_creator)

    async def _injected() -> str:
        async with MyContainer.slow_provider.async_context():
            return await MyContainer.slow_provider.async_resolve()

    await asyncio.gather(*[_injected() for _ in range(10)])

[lesnik512]

@alexanderlazarev0 should we release 2.0.0 or you have some ideas or concerns?

[alexanderlazarev0]

I have still a few things I think we should do before 2.0.0 release (listed by priority):

• Test latest pre-release on a larger ASGI application (My last test was with 2.0.0.a2)
• Add a warning when overriding existing container (only relevant for string providers)
• Change the default of preserve_global_context in container_context() and DiContextMiddleware to true since a "global" context should not be so easy to reset.
• Fix documentation (some sections and especially enumerated lists do not show up correctly).
• Expand the documentation of some sections for clarity
• @lesnik512 There seems to be some difference in the deployment configuration in ReadTheDocs, for example test-docs clearly show that we are on the latest version of the docs. Could you please configure it to per default show the stable version of the docs. (For example, the last few weeks the documentation any reader was seeing was the 2.0.0a* documentation instead of 1.27.0, this should not be the case as docs should per default point to a release).

[lesnik512]

Will do #155

[alexanderlazarev0]

All points done in #156