Exception in Destructor

[DasCapschen]

When a Postgres Connection is deleted, it encounters an Exception in its Constructor, which is fortunately ignored.
Yet it is a little concerning, that the destructor does not finish successfully.

Code is approximately:

connection = create_postgres_connection()
db_migrator = Migrator(connection=connection)
db_migrator.migrate()
connection.close()
# script ends and destructor is called

The error message is:

Exception ignored in: <function BaseConnection.__del__ at 0x7f6c249bdbc0>
Traceback (most recent call last):
  File "/opt/maddox/.venv/lib/python3.11/site-packages/psycopg/connection.py", line 157, in __del__
  File "/opt/maddox/.venv/lib/python3.11/site-packages/psycopg/connection.py", line 164, in __repr__
AttributeError: 'NoneType' object has no attribute 'connection_summary'

Versions are:

• Python 3.11.4
• Psycopg 3.1.9
• libpg 15.3 (Debian)
• Postgres 15.2 (Alpine Docker Container)

[dvarrazzo]

It seems a problem similar to #198. The `connection_summary` function is pretty complex and I wouldn't try to create all the closures to make it work at destruction time because it's untestable. If any I'd try to make repr work, in a degenerate way, on AttributeError.

…

On Tue, 4 Jul 2023, 13:24 Dominik Waurenschk, ***@***.***> wrote: When a Postgres Connection is deleted, it encounters an Exception in its Constructor, which is fortunately ignored. Yet it is a little concerning, that the destructor does not finish successfully. Code is approximately: connection = create_postgres_connection()db_migrator = Migrator(connection=connection)db_migrator.migrate()connection.close()# script ends and destructor is called The error message is: Exception ignored in: <function BaseConnection.__del__ at 0x7f6c249bdbc0> Traceback (most recent call last): File "/opt/maddox/.venv/lib/python3.11/site-packages/psycopg/connection.py", line 157, in __del__ File "/opt/maddox/.venv/lib/python3.11/site-packages/psycopg/connection.py", line 164, in __repr__ AttributeError: 'NoneType' object has no attribute 'connection_summary' Versions are: - Python 3.11.4 - Psycopg 3.1.9 - libpg 15.3 (Debian) - Postgres 15.2 (Alpine Docker Container) — Reply to this email directly, view it on GitHub <#591>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABQWBOTRUOGN4PH23X4SZ3XOP4N3ANCNFSM6AAAAAAZ5TC6SQ> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[DasCapschen]

But the problem does not seem to be in the connection_summary function. Instead it already fails when trying to call the connection_summary function. Whatever Object that function is called on, it was already destroyed and does not exist anymore.

[dvarrazzo]

Yes, what I meant is that, when the problem was encountered the first time, for instance with an attribute error on `os.getpid`, the solution was "just store the `getpid` function in a local var". This works for simple atomic functions such as getpid, implemented in c and executed in a single python opcode, but I doubt it would work for connection_summary: it is likely, and not reliably testable, that an attribute error might get raised in its body because of some module already gc'ed.

[DasCapschen]

Ah, now I understand what you mean. Seems like it is a Python bug then, if it GC's things that are still used in destructors...
Well okay... guess we'll just keep ignoring this then 😅

[dvarrazzo]

No, not necessarily, we can make it more robust. We can manage an error on repr() called within del() for instance, and provide a simplified error message. For instance, untested: ``` try: r = repr(self) except Exception: r = object.repr(self) # does it work? warn(f"connection {r} was deleted... ``` If you have a somewhat repeatable test case, it would be actually nice if you could test it and provide a MR for this and other occurrences of messages raised in del.

[dvarrazzo]

A fix for this error will be released in 3.1.10.

[DasCapschen]

Wow thank you! I will test this as soon as the release is out :)