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Keep thread pool executors around. #306

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Keep thread pool executors around. #306

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24 changes: 20 additions & 4 deletions asgiref/sync.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,9 @@
contextvars = None


SYNC_POOL_WORKER_COUNT = 10 # TODO: this is random for testing now


def _restore_context(context):
# Check for changes in contextvars, and set them to the current
# context for downstream consumers
Expand Down Expand Up @@ -84,9 +87,7 @@ async def __aexit__(self, exc, value, tb):
if not self.token:
return

executor = SyncToAsync.context_to_thread_executor.pop(self, None)
if executor:
executor.shutdown()
SyncToAsync.release_executor(self)
SyncToAsync.thread_sensitive_context.reset(self.token)

else:
Expand Down Expand Up @@ -343,6 +344,8 @@ class SyncToAsync:
# Single-thread executor for thread-sensitive code
single_thread_executor = ThreadPoolExecutor(max_workers=1)

executor_pool = []

# Maintain a contextvar for the current execution context. Optionally used
# for thread sensitive mode.
if sys.version_info >= (3, 7):
Expand Down Expand Up @@ -407,7 +410,10 @@ async def __call__(self, *args, **kwargs):
executor = self.context_to_thread_executor[thread_sensitive_context]
else:
# Create new thread executor in current context
executor = ThreadPoolExecutor(max_workers=1)
try:
executor = self.executor_pool.pop()
except IndexError:
executor = ThreadPoolExecutor(max_workers=1)
self.context_to_thread_executor[thread_sensitive_context] = executor
elif self.deadlock_context and self.deadlock_context.get(False):
raise RuntimeError(
Expand Down Expand Up @@ -506,6 +512,16 @@ def get_current_task():
except RuntimeError:
return None

@classmethod
def release_executor(cls, obj):
executor = cls.context_to_thread_executor.pop(obj, None)
if executor is None:
return
if len(cls.executor_pool) < SYNC_POOL_WORKER_COUNT:
cls.executor_pool.append(executor)
else:
executor.shutdown()


# Lowercase aliases (and decorator friendliness)
async_to_sync = AsyncToSync
Expand Down