fix: set multiprocessing context according to OS

Author: ClemDoum

neo4j-app/neo4j_app/app/dependencies.py

@@ -3,6 +3,7 @@
 import logging
 import multiprocessing
 import os
+import platform
 import sys
 import tempfile
 import traceback
@@ -37,6 +38,7 @@
 _TEST_DB_FILE: Optional[Path] = None
 _TEST_LOCK: Optional[multiprocessing.Lock] = None
 _PROCESS_EXECUTOR: Optional[concurrent.futures.ProcessPoolExecutor] = None
+_MP_CONTEXT = None
 
 
 class DependencyInjectionError(RuntimeError):
@@ -63,6 +65,24 @@ def lifespan_config() -> AppConfig:
     return cast(AppConfig, _CONFIG)
 
 
+def mp_context_enter(**__):
+    global _MP_CONTEXT
+    platform_system = platform.system()
+    if platform_system == "Darwin":
+        ctx = "spawn"
+    elif platform_system == "Linux":
+        ctx = "fork"
+    else:
+        raise ValueError(f"Unsupported OS: {platform_system}")
+    _MP_CONTEXT = multiprocessing.get_context(ctx)
+
+
+def lifespan_mp_context():
+    if _MP_CONTEXT is None:
+        raise DependencyInjectionError("multiprocessing context")
+    return _MP_CONTEXT
+
+
 async def neo4j_driver_enter(**__):
     global _NEO4J_DRIVER
     _NEO4J_DRIVER = lifespan_config().to_neo4j_driver()
@@ -164,7 +184,7 @@ def process_executor_enter(**_):
     worker_ids = [f"worker-{process_id}-{i}" for i in range(n_workers)]
     _PROCESS_EXECUTOR = concurrent.futures.ProcessPoolExecutor(  # pylint: disable=unnecessary-dunder-call
         max_workers=n_workers,
-        mp_context=multiprocessing.get_context("spawn"),
+        mp_context=lifespan_mp_context(),
     ).__enter__()
     kwargs = dict()
     worker_cls = config.to_worker_cls()
@@ -261,6 +281,7 @@ def lifespan_event_publisher() -> EventPublisher:
     ("neo4j driver creation", neo4j_driver_enter, neo4j_driver_exit),
     ("neo4j project registry creation", create_project_registry_db_enter, None),
     ("ES client creation", es_client_enter, es_client_exit),
+    (None, mp_context_enter, None),
     (None, test_process_manager_enter, test_process_manager_exit),
     (None, test_db_path_enter, test_db_path_exit),
     (None, _test_lock_enter, None),