Merge pull request #642 from FabienArcellier/WF-114-the-process-of-sa…

…ving-project-information-stops-in-a-predictable-manner

fix: the process of saving project information stops properly in any condition - WF-114

src/writer/app_runner.py

@@ -634,17 +634,6 @@ def _start_wf_project_process_write_files(self):
         wf_project.start_process_write_files_async(self.wf_project_context, AppRunner.WF_PROJECT_SAVE_INTERVAL)
 
     def load(self) -> None:
-        def signal_handler(sig, frame):
-            self.shut_down()
-            sys.exit(0)
-
-        try:
-            signal.signal(signal.SIGINT, signal_handler)
-            signal.signal(signal.SIGTERM, signal_handler)
-        except ValueError:
-            # No need to handle signal as not main thread
-            pass
-
         self.run_code = self._load_persisted_script()
         self.bmc_components = self._load_persisted_components()
 
@@ -654,6 +643,13 @@ def signal_handler(sig, frame):
 
         self._start_app_process()
 
+        # We have to create new processes as wf_projet_process before subscribing to signal.
+        # When a new process is create, the parent process is fork. The child would also subscribe to signal.
+        #
+        # When signal happen, both process will answer and one of them raise error due to mismatch between
+        # parent pid and pid.
+        self._subscribe_terminal_signal()
+
     async def dispatch_message(self, session_id: Optional[str], request: AppProcessServerRequest) -> AppProcessServerResponse:
 
         """
@@ -885,3 +881,15 @@ def run_async_in_thread():
         thread.start()
         thread.join()
         return
+
+    def _subscribe_terminal_signal(self):
+        def signal_handler(sig, frame):
+            self.shut_down()
+            sys.exit(0)
+
+        try:
+            signal.signal(signal.SIGINT, signal_handler)
+            signal.signal(signal.SIGTERM, signal_handler)
+        except ValueError:
+            # No need to handle signal as not main thread
+            pass

src/writer/wf_project.py

@@ -11,6 +11,7 @@
 import logging
 import multiprocessing
 import os
+import queue
 import time
 import typing
 from collections import OrderedDict
@@ -30,6 +31,7 @@ class WfProjectContext:
     app_path: str
     write_files_async_queue: Queue = Queue()
     write_files_async_process: typing.Optional[multiprocessing.Process] = None
+    write_files_async_stop: Any = multiprocessing.Event() # Note: Event is a function, not a class in python, it can't be typed
 
 
 def write_files_async(context: WfProjectContext, metadata: MetadataDefinition, components: Dict[str, ComponentDefinition]) -> None:
@@ -77,9 +79,10 @@ def start_process_write_files_async(context: WfProjectContext, save_interval: fl
     :param wf_project_save_interval: the interval in seconds to save the project files
     :return:
     """
-
-
-    p = multiprocessing.Process(target=_start_process_write_files_async_process, args=(context, save_interval,))
+    p = multiprocessing.Process(
+        target=_start_process_write_files_async_process,
+        args=(context, save_interval, context.write_files_async_stop)
+    )
     context.write_files_async_process = p
     p.start()
 
@@ -88,9 +91,12 @@ def shutdown_process_write_files_async(context: WfProjectContext) -> None:
     """
     Shutdown the process that writes the .wf/ files
     """
-    if context.write_files_async_process is not None:
-        context.write_files_async_process.terminate()
+    if context.write_files_async_process is not None and \
+        context.write_files_async_process.is_alive():
+        context.write_files_async_stop.set()
         context.write_files_async_process.join()
+        context.write_files_async_process = None
+        context.write_files_async_stop.clear()
 
 def read_files(app_path: str) -> Tuple[MetadataDefinition, dict[str, ComponentDefinition]]:
     """
@@ -271,9 +277,16 @@ def _hierarchical_position(components, c):
     return sorted(components.values(), key=lambda c: _hierarchical_position(components, c))
 
 
-def _start_process_write_files_async_process(context: WfProjectContext, save_interval):
+def _start_process_write_files_async_process(context: WfProjectContext, save_interval, stop_event):
     while True:
-        obj = context.write_files_async_queue.get()
+        if stop_event.is_set():
+            break
+
+        try:
+            obj = context.write_files_async_queue.get(block=False)
+        except queue.Empty:
+            obj = None
+
         if obj is not None:
             app_path, metadata, components = obj
             write_files(app_path, metadata, components)