Exception in Destructor #591
Comments
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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)
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But the problem does not seem to be in the |
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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.
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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... |
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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.
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dvarrazzo
added a commit
that referenced
this issue
Jul 23, 2023
The errors get ignored but print a warning on program exit and eclipse a genuine warning. The error is caused by the `pq.misc` module getting gc'd on interpreter shutdown before `connection_summary()` is called. The solution is to import `connection_summary` in the module namespace, which is similar to the solution that proved working for #198. It is less robust than the solution used by the Python devs to import the function in the method via an argument default, but it should work adequately (as nobody complained about #198 anymore). In #591 discussion, I proposed that connection_summary is too complex to be considered safe to call on __del__. Actually, looking at it, it seems innocent enough, as it only calls objects methods, no functions from module namespaces. As a consequence we assume that this commit fixes the issue. As I can't reproduce it, will ask the OP if this is the case. Close #591.
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A fix for this error will be released in 3.1.10. |
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Wow thank you! I will test this as soon as the release is out :) |
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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:
The error message is:
Versions are:
The text was updated successfully, but these errors were encountered: