I suppose here is a memory leak. cattrs converter function use linecache by default to store a byte code of the generated converted function, so each time we called _get_cattrs_converter our custom dict function is cached.
POC
Click to expand
```python
from appstoreserverlibrary.models.JWSTransactionDecodedPayload import JWSTransactionDecodedPayload
from appstoreserverlibrary.models.LibraryUtility import _get_cattrs_converter
import gc
def leaky_function():
c = _get_cattrs_converter(JWSTransactionDecodedPayload) # cattrs.Converter()
c.structure(
{"originalTransactionId": "123"},
JWSTransactionDecodedPayload,
)
def count_objects_by_type():
gc.collect()
type_count = {}
for obj in gc.get_objects():
obj_type = type(obj)
type_count[obj_type] = type_count.get(obj_type, 0) + 1
return type_count
def diff_snapshots(before, after):
diff = {}
for key in after:
before_count = before.get(key, 0)
after_count = after[key]
if after_count != before_count:
diff[key] = (before_count, after_count, after_count - before_count)
for key in before:
if key not in after:
diff[key] = (before[key], 0, -before[key])
return diff
def print_diff(diff):
sorted_diff = sorted(diff.items(), key=lambda item: abs(item[1][2]), reverse=True)
print("Type | Before | After | Diff")
print("---------------------|--------|-------|------")
for key, (before_count, after_count, diff_count) in sorted_diff:
print(
f"{key.__name__:<20} | {before_count:6} | {after_count:6} | {diff_count:+6}")
def test_memory_leak():
print("Taking snapshot before calling leaky_function...")
before = count_objects_by_type()
# Call the suspected leaky function multiple times
for _ in range(1000):
leaky_function()
print("Taking snapshot after calling leaky_function...")
after = count_objects_by_type()
diff = diff_snapshots(before, after)
print_diff(diff)
if __name__ == "__main__":
test_memory_leak()
```
```
Taking snapshot before calling leaky_function...
Taking snapshot after calling leaky_function...
Type | Before | After | Diff
---------------------|--------|-------|------
list | 460 | 1460 | +1000
tuple | 2052 | 3052 | +1000
dict | 1493 | 1497 | +4
```
I suppose here is a memory leak. cattrs converter function use
linecacheby default to store a byte code of the generated converted function, so each time we called_get_cattrs_converterour custom dict function is cached.POC
Click to expand
```python from appstoreserverlibrary.models.JWSTransactionDecodedPayload import JWSTransactionDecodedPayload from appstoreserverlibrary.models.LibraryUtility import _get_cattrs_converter import gc def leaky_function(): c = _get_cattrs_converter(JWSTransactionDecodedPayload) # cattrs.Converter() c.structure( {"originalTransactionId": "123"}, JWSTransactionDecodedPayload, ) def count_objects_by_type(): gc.collect() type_count = {} for obj in gc.get_objects(): obj_type = type(obj) type_count[obj_type] = type_count.get(obj_type, 0) + 1 return type_count def diff_snapshots(before, after): diff = {} for key in after: before_count = before.get(key, 0) after_count = after[key] if after_count != before_count: diff[key] = (before_count, after_count, after_count - before_count) for key in before: if key not in after: diff[key] = (before[key], 0, -before[key]) return diff def print_diff(diff): sorted_diff = sorted(diff.items(), key=lambda item: abs(item[1][2]), reverse=True) print("Type | Before | After | Diff") print("---------------------|--------|-------|------") for key, (before_count, after_count, diff_count) in sorted_diff: print( f"{key.__name__:<20} | {before_count:6} | {after_count:6} | {diff_count:+6}") def test_memory_leak(): print("Taking snapshot before calling leaky_function...") before = count_objects_by_type() # Call the suspected leaky function multiple times for _ in range(1000): leaky_function() print("Taking snapshot after calling leaky_function...") after = count_objects_by_type() diff = diff_snapshots(before, after) print_diff(diff) if __name__ == "__main__": test_memory_leak() ``` ``` Taking snapshot before calling leaky_function... Taking snapshot after calling leaky_function... Type | Before | After | Diff ---------------------|--------|-------|------ list | 460 | 1460 | +1000 tuple | 2052 | 3052 | +1000 dict | 1493 | 1497 | +4 ```Leaking code
https://github.com/apple/app-store-server-library-python/blob/26f2682ab2f0ff44ce5a93d8c1ce10ebbcc6a253/appstoreserverlibrary/models/LibraryUtility.py#L67-L68
Possible fix
Looks like we can cache entirely
_get_cattrs_converteror disable line caching at the cattrs