Taragolis opened a new pull request, #37757:
URL: https://github.com/apache/airflow/pull/37757
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This is attempt to prevent use `functools.lru_cache` or `functools.cache` on
methods which lead to memory leak, e.g. object can't be garbage collected if it
use methods decorated by this decorators.
Simple reproducible example
```python
import functools
class A:
def __init__(self):
self.a = {"a": 1, "b": 2}
@functools.lru_cache(maxsize=None)
def get_val(self, key: str):
return self.a[key]
for _ in range(100):
xxx = A()
xxx.get_val(key="a")
xxx.get_val("a")
xxx.get_val("b")
del xxx
import gc
gc.collect()
a_instances = [o for o in gc.get_objects() if isinstance(o, A)]
assert len(a_instances) == 0, len(a_instances)
# AssertionError: 100
```
Instead of that better to use use `functools.cached_property` (if it could
be a property), ruff [`B018`
rule](https://docs.astral.sh/ruff/rules/cached-instance-method/#example)
suggestion or use some third-party library, e.g.
[`methodtools`](https://github.com/youknowone/methodtools/)
```python
import methodtools
class A:
def __init__(self):
self.a = {"a": 1, "b": 2}
@methodtools.lru_cache(maxsize=None)
def get_val(self, key: str):
return self.a[key]
for _ in range(100):
xxx = A()
xxx.get_val(key="a")
xxx.get_val(key="a")
xxx.get_val("b")
del xxx
import gc
gc.collect()
a_instances = [o for o in gc.get_objects() if isinstance(o, A)]
assert len(a_instances) == 0, len(a_instances) # Do not raise assertion error
```
- ruff do not detect `compat` decorator `airflow.compat.functools.cache` for
avoid use it in methods use simple pre-commit check. It is only required until
we have Python 3.9 as min version, and do not use
`airflow.compat.functools.cache` in code base.
- There is couple of places where cache used into the Airflow core, some of
them might be a result of memory leakage, the simple way is use
`methodtools.lru_cache` - this one would not breaks public interfaces or
behaviour and do no required to rewrite. In another word we have bug fix "Here
and Now" instead of think how to rewrite without additional dependency.
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