Mysql issue using afirst "The client was disconnected by the server because of inactivity"

[Bernardo Tavares]

I'm using Django 4.2 connected to a MySQL 8 database.
I'm running asyncio for a function I really need to run asynchronously:

from django.db import connection
import asyncio

example_object = asyncio.run(example(request))
connection.close()

async def example(request):
    object = await ModelExample.objects.filter(example=example).afirst()
    return object

I'm having the following error:
"The client was disconnected by the server because of inactivity. See wait_timeout and interactive_timeout for configuring this behavior"

Initially the work codes fine, the error only happens after a few hours (maybe 8h, like the default wait_timeout variable) after I restart the (nginx) server.
It's a low traffic website so it's very possible the function is executed only once a day.

In my understanding, Django always opens a connection, executes a query and then closes a connection.
Is it not closing the connection when using "afirst()"? This feels seems like a bug to me, or is something in the documentation I'm not getting.

Any help? Thank you in advance!

---

Other things that I tried:

• Before doing the connection.close(), I would have an error like: "MySQL server has gone away"
• Adding close_old_connections() before asyncio.run. Don't understand why there is an inactive connection left open at all.
• Increasing the wait_timeout value and interactive_timeout variables in my MySQL config file. I find it very strange that this had no impact at all but the "SHOW VARIABLES" command shows me they are indeed currently set to 31536000.
• Then I thought that maybe the connection from Django is somehow independent of that and tried setting CONN_HEALTH_CHECKS option to True, in the hopes that "if the health check fails, the connection will be re-established without failing the request"
• Changing the CONN_MAX_AGE from the default 0 to "None" in the Django settings file, which according to Django docs, means an unlimited persistent database connection, but then I would have a "Lost connection to MySQL server during query"

[Natalia Bidart]

I wonder if this is related to #33497...

Bernardo, do you think you could provide a minimal (but complete) example to reproduce this issue? Thanks!

[Mariusz Felisiak]

In my understanding, Django always opens a connection, executes a query and then closes a connection.

Yes, if you're talking about request-response cycle and connections are not persistent.

Is it not closing the connection when using "afirst()"? This feels seems like a bug to me, or is something in the documentation I'm not getting.

As far as I'm aware, this has nothing to do with afirst().

Any help? Thank you in advance!

I don't think you've explained the issue in enough detail to confirm a bug in Django and Trac is not a support channel. Please reopen the ticket if you can debug your issue and provide details about why and where Django is at fault. A small project that reproduces the issue will also help. If you're having trouble debugging, see TicketClosingReasons/UseSupportChannels for ways to get help.

[Bernardo Tavares]

Replying to Natalia Bidart:

I wonder if this is related to #33497...

Bernardo, do you think you could provide a minimal (but complete) example to reproduce this issue? Thanks!

I'm using unicorn with wsgi. Sure!

[Bernardo Tavares]

Replying to Mariusz Felisiak:

In my understanding, Django always opens a connection, executes a query and then closes a connection.

Yes, if you're talking about request-response cycle and connections are not persistent.

Is it not closing the connection when using "afirst()"? This feels seems like a bug to me, or is something in the documentation I'm not getting.

As far as I'm aware, this has nothing to do with afirst().

Any help? Thank you in advance!

I don't think you've explained the issue in enough detail to confirm a bug in Django and Trac is not a support channel. Please reopen the ticket if you can debug your issue and provide details about why and where Django is at fault. A small project that reproduces the issue will also help. If you're having trouble debugging, see TicketClosingReasons/UseSupportChannels for ways to get help.

Understood. I will try to go deeper on this.
I opened a forum discussion here ​https://forum.djangoproject.com/t/debugging-the-client-was-disconnected-by-the-server-because-of-inactivity/21730 , if you can help me debug a bit further and explain why this is not related with afirst() I would be grateful.