diff options
Diffstat (limited to 'Lib/concurrent')
| -rw-r--r-- | Lib/concurrent/futures/process.py | 24 |
1 files changed, 17 insertions, 7 deletions
diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py index 0d49379c..821034d 100644 --- a/Lib/concurrent/futures/process.py +++ b/Lib/concurrent/futures/process.py @@ -617,14 +617,16 @@ class ProcessPoolExecutor(_base.Executor): execute the given calls. If None or not given then as many worker processes will be created as the machine has processors. mp_context: A multiprocessing context to launch the workers. This - object should provide SimpleQueue, Queue and Process. + object should provide SimpleQueue, Queue and Process. Useful + to allow specific multiprocessing start methods. initializer: A callable used to initialize worker processes. initargs: A tuple of arguments to pass to the initializer. - max_tasks_per_child: The maximum number of tasks a worker process can - complete before it will exit and be replaced with a fresh - worker process, to enable unused resources to be freed. The - default value is None, which means worker process will live - as long as the executor will live. + max_tasks_per_child: The maximum number of tasks a worker process + can complete before it will exit and be replaced with a fresh + worker process. The default of None means worker process will + live as long as the executor. Requires a non-'fork' mp_context + start method. When given, we default to using 'spawn' if no + mp_context is supplied. """ _check_system_limits() @@ -644,7 +646,10 @@ class ProcessPoolExecutor(_base.Executor): self._max_workers = max_workers if mp_context is None: - mp_context = mp.get_context() + if max_tasks_per_child is not None: + mp_context = mp.get_context("spawn") + else: + mp_context = mp.get_context() self._mp_context = mp_context if initializer is not None and not callable(initializer): @@ -657,6 +662,11 @@ class ProcessPoolExecutor(_base.Executor): raise TypeError("max_tasks_per_child must be an integer") elif max_tasks_per_child <= 0: raise ValueError("max_tasks_per_child must be >= 1") + if self._mp_context.get_start_method(allow_none=False) == "fork": + # https://github.com/python/cpython/issues/90622 + raise ValueError("max_tasks_per_child is incompatible with" + " the 'fork' multiprocessing start method;" + " supply a different mp_context.") self._max_tasks_per_child = max_tasks_per_child # Management thread |