121 lines
4.7 KiB
Python
121 lines
4.7 KiB
Python
import random
|
|
import string
|
|
import sys
|
|
import threading
|
|
import weakref
|
|
|
|
|
|
class Local:
|
|
"""
|
|
A drop-in replacement for threading.locals that also works with asyncio
|
|
Tasks (via the current_task asyncio method), and passes locals through
|
|
sync_to_async and async_to_sync.
|
|
|
|
Specifically:
|
|
- Locals work per-coroutine on any thread not spawned using asgiref
|
|
- Locals work per-thread on any thread not spawned using asgiref
|
|
- Locals are shared with the parent coroutine when using sync_to_async
|
|
- Locals are shared with the parent thread when using async_to_sync
|
|
(and if that thread was launched using sync_to_async, with its parent
|
|
coroutine as well, with this working for indefinite levels of nesting)
|
|
|
|
Set thread_critical to True to not allow locals to pass from an async Task
|
|
to a thread it spawns. This is needed for code that truly needs
|
|
thread-safety, as opposed to things used for helpful context (e.g. sqlite
|
|
does not like being called from a different thread to the one it is from).
|
|
Thread-critical code will still be differentiated per-Task within a thread
|
|
as it is expected it does not like concurrent access.
|
|
|
|
This doesn't use contextvars as it needs to support 3.6. Once it can support
|
|
3.7 only, we can then reimplement the storage more nicely.
|
|
"""
|
|
|
|
def __init__(self, thread_critical: bool = False) -> None:
|
|
self._thread_critical = thread_critical
|
|
self._thread_lock = threading.RLock()
|
|
self._context_refs: "weakref.WeakSet[object]" = weakref.WeakSet()
|
|
# Random suffixes stop accidental reuse between different Locals,
|
|
# though we try to force deletion as well.
|
|
self._attr_name = "_asgiref_local_impl_{}_{}".format(
|
|
id(self),
|
|
"".join(random.choice(string.ascii_letters) for i in range(8)),
|
|
)
|
|
|
|
def _get_context_id(self):
|
|
"""
|
|
Get the ID we should use for looking up variables
|
|
"""
|
|
# Prevent a circular reference
|
|
from .sync import AsyncToSync, SyncToAsync
|
|
|
|
# First, pull the current task if we can
|
|
context_id = SyncToAsync.get_current_task()
|
|
context_is_async = True
|
|
# OK, let's try for a thread ID
|
|
if context_id is None:
|
|
context_id = threading.current_thread()
|
|
context_is_async = False
|
|
# If we're thread-critical, we stop here, as we can't share contexts.
|
|
if self._thread_critical:
|
|
return context_id
|
|
# Now, take those and see if we can resolve them through the launch maps
|
|
for i in range(sys.getrecursionlimit()):
|
|
try:
|
|
if context_is_async:
|
|
# Tasks have a source thread in AsyncToSync
|
|
context_id = AsyncToSync.launch_map[context_id]
|
|
context_is_async = False
|
|
else:
|
|
# Threads have a source task in SyncToAsync
|
|
context_id = SyncToAsync.launch_map[context_id]
|
|
context_is_async = True
|
|
except KeyError:
|
|
break
|
|
else:
|
|
# Catch infinite loops (they happen if you are screwing around
|
|
# with AsyncToSync implementations)
|
|
raise RuntimeError("Infinite launch_map loops")
|
|
return context_id
|
|
|
|
def _get_storage(self):
|
|
context_obj = self._get_context_id()
|
|
if not hasattr(context_obj, self._attr_name):
|
|
setattr(context_obj, self._attr_name, {})
|
|
self._context_refs.add(context_obj)
|
|
return getattr(context_obj, self._attr_name)
|
|
|
|
def __del__(self):
|
|
try:
|
|
for context_obj in self._context_refs:
|
|
try:
|
|
delattr(context_obj, self._attr_name)
|
|
except AttributeError:
|
|
pass
|
|
except TypeError:
|
|
# WeakSet.__iter__ can crash when interpreter is shutting down due
|
|
# to _IterationGuard being None.
|
|
pass
|
|
|
|
def __getattr__(self, key):
|
|
with self._thread_lock:
|
|
storage = self._get_storage()
|
|
if key in storage:
|
|
return storage[key]
|
|
else:
|
|
raise AttributeError(f"{self!r} object has no attribute {key!r}")
|
|
|
|
def __setattr__(self, key, value):
|
|
if key in ("_context_refs", "_thread_critical", "_thread_lock", "_attr_name"):
|
|
return super().__setattr__(key, value)
|
|
with self._thread_lock:
|
|
storage = self._get_storage()
|
|
storage[key] = value
|
|
|
|
def __delattr__(self, key):
|
|
with self._thread_lock:
|
|
storage = self._get_storage()
|
|
if key in storage:
|
|
del storage[key]
|
|
else:
|
|
raise AttributeError(f"{self!r} object has no attribute {key!r}")
|