fix(flags): Fix bug where concurrent accesses to the flags property could raise a RunTime error

[cmanallen]

On error the SDK deep copies the flag buffer. If the SDK is receiving flags at the same time, the buffer copy can potentially raise a RunTime error. To fix this we guard the FlagBuffer with a lock.

Fixes: https://sentry.sentry.io/issues/6286673308/?project=1

[codecov]

❌ 54 Tests Failed:

Tests completed	Failed	Passed	Skipped
22316	54	22262	5758

View the top 3 failed test(s) by shortest run time

pytest internal

Stack Traces | 0s run time

Traceback (most recent call last):
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7...................../site-packages/coverage/sqldata.py", line 1173, in _execute
    return self.con.execute(sql, parameters)    # type: ignore[arg-type]
sqlite3.OperationalError: no such table: file

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7...................../site-packages/coverage/sqldata.py", line 1178, in _execute
    return self.con.execute(sql, parameters)    # type: ignore[arg-type]
sqlite3.OperationalError: no such table: file

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7....../site-packages/_pytest/main.py", line 271, in wrap_session
    session.exitstatus = doit(config, session) or 0
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7....../site-packages/_pytest/main.py", line 325, in _main
    config.hook.pytest_runtestloop(session=session)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7.../site-packages/pluggy/_hooks.py", line 433, in __call__
    return self._hookexec(self.name, self._hookimpls, kwargs, firstresult)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7.../site-packages/pluggy/_manager.py", line 112, in _hookexec
    return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7.../site-packages/pluggy/_callers.py", line 133, in _multicall
    teardown[0].send(outcome)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7.../site-packages/pytest_cov/plugin.py", line 298, in pytest_runtestloop
    self.cov_controller.finish()
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7....../site-packages/pytest_cov/engine.py", line 44, in ensure_topdir_wrapper
    return meth(self, *args, **kwargs)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7....../site-packages/pytest_cov/engine.py", line 249, in finish
    self.cov.stop()
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7........./site-packages/coverage/control.py", line 757, in save
    data = self.get_data()
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7........./site-packages/coverage/control.py", line 838, in get_data
    self._post_save_work()
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7........./site-packages/coverage/control.py", line 869, in _post_save_work
    self._data.touch_files(paths, plugin_name)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7...................../site-packages/coverage/sqldata.py", line 615, in touch_files
    self._file_id(filename, add=True)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7...................../site-packages/coverage/sqldata.py", line 419, in _file_id
    (filename,)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7...................../site-packages/coverage/sqldata.py", line 1219, in execute_for_rowid
    with self.execute(sql, parameters) as cur:
  File ".../hostedtoolcache/Python/3.7.17.../x64/lib/python3.7/contextlib.py", line 112, in __enter__
    return next(self.gen)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7...................../site-packages/coverage/sqldata.py", line 1207, in execute
    cur = self._execute(sql, parameters)
  File ".../sentry-python/sentry-python/.tox/py3.7-falcon-v1.4/lib/python3.7...................../site-packages/coverage/sqldata.py", line 1195, in _execute
    raise DataError(f"Couldn't use data file {self.filename!r}: {msg}") from exc
coverage.exceptions.DataError: Couldn't use data file '.../sentry-python/sentry-python/.coverage-sentry-py3.7-falcon-v1.4.fv-az890-162.3327.489845': no such table: file

tests.integrations.strawberry.test_strawberry test_handle_none_query_gracefully[async_app_client_factory-True-framework_integrations0]

Stack Traces | 0.064s run time

.../integrations/strawberry/test_strawberry.py:631: in test_handle_none_query_gracefully
    sentry_init(
tests/conftest.py:203: in inner
    client = sentry_sdk.Client(*a, **kw)
sentry_sdk/client.py:269: in __init__
    self._init_impl()
sentry_sdk/client.py:392: in _init_impl
    self.integrations = setup_integrations(
sentry_sdk/integrations/__init__.py:196: in setup_integrations
    type(integration).setup_once()
sentry_sdk/integrations/strawberry.py:81: in setup_once
    _patch_execute()
sentry_sdk/integrations/strawberry.py:293: in _patch_execute
    old_execute_sync = strawberry_schema.execute_sync
E   AttributeError: module 'strawberry.schema.schema' has no attribute 'execute_sync'

tests.integrations.strawberry.test_strawberry test_span_origin[sync_app_client_factory-False-framework_integrations1]

Stack Traces | 0.064s run time

.../integrations/strawberry/test_strawberry.py:661: in test_span_origin
    sentry_init(
tests/conftest.py:203: in inner
    client = sentry_sdk.Client(*a, **kw)
sentry_sdk/client.py:269: in __init__
    self._init_impl()
sentry_sdk/client.py:392: in _init_impl
    self.integrations = setup_integrations(
sentry_sdk/integrations/__init__.py:196: in setup_integrations
    type(integration).setup_once()
sentry_sdk/integrations/strawberry.py:81: in setup_once
    _patch_execute()
sentry_sdk/integrations/strawberry.py:293: in _patch_execute
    old_execute_sync = strawberry_schema.execute_sync
E   AttributeError: module 'strawberry.schema.schema' has no attribute 'execute_sync'

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[cmanallen]

@antonpirker Strawberry integration seems broken for unrelated reasons.

[antoniobg]

Apologies if this isn’t the right place to ask. We started a discussion about this fix but haven't received a response.

We’ve been testing the new feature flag functionality (currently in beta) and ran into an issue that appears to have been addressed by #4034
The fix introduces a lock to prevent concurrency issues, but we were wondering why FlagBuffered is shared across contexts rather than being thread-local. Wouldn’t it make more sense for it to be per-context to avoid the need for locking?
Thanks in advance for your help!

[cmanallen]

@antoniobg This is a fine place. Discussions don't send Slack notifications so apologies I missed it. Thanks for raising. I'll respond on the discussion topic to keep everything in one place.