Best-effort flush events at shutdown (#15331)

src/app/reporting/Engine.cpp

@@ -42,6 +42,9 @@ CHIP_ERROR Engine::Init()
 
 void Engine::Shutdown()
 {
+    // Flush out the event buffer synchronously
+    ScheduleUrgentEventDeliverySync();
+
     mNumReportsInFlight = 0;
     mCurReadHandlerIdx  = 0;
     mGlobalDirtySet.ReleaseAll();
@@ -746,6 +749,22 @@ CHIP_ERROR Engine::ScheduleEventDelivery(ConcreteEventPath & aPath, EventOptions
     return CHIP_NO_ERROR;
 }
 
+void Engine::ScheduleUrgentEventDeliverySync()
+{
+    InteractionModelEngine::GetInstance()->mReadHandlers.ForEachActiveObject([](ReadHandler * handler) {
+        if (handler->IsType(ReadHandler::InteractionType::Read))
+        {
+            return Loop::Continue;
+        }
+
+        handler->UnblockUrgentEventDelivery();
+
+        return Loop::Continue;
+    });
+
+    Run();
+}
+
 }; // namespace reporting
 } // namespace app
 } // namespace chip

src/app/reporting/Engine.h

@@ -146,6 +146,7 @@ class Engine
     CHIP_ERROR ScheduleUrgentEventDelivery(ConcreteEventPath & aPath);
     CHIP_ERROR ScheduleBufferPressureEventDelivery(uint32_t aBytesWritten);
     void GetMinEventLogPosition(uint32_t & aMinLogPosition);
+    void ScheduleUrgentEventDeliverySync();
 
     /**
      * If the provided path is a superset of our of our existing paths, update that existing path to match the