[DO NOT MERGE] Revert "Restructure cleaning up of the futures in deco…

…upled mode (#309) (#311)"

This reverts commit d2bcb22.

src/python_be.cc

@@ -811,7 +811,9 @@ ModelInstanceState::DecoupledMessageQueueMonitor()
       std::packaged_task<void()> task([this, response_send_message] {
         ResponseSendDecoupled(response_send_message);
       });
-      boost::asio::post(*thread_pool_, std::move(task));
+      std::future<void> future =
+          boost::asio::post(*thread_pool_, std::move(task));
+      futures_.emplace_back(std::move(future));
     } else if (
         message->Command() == PYTHONSTUB_InferExecRequest ||
         message->Command() == PYTHONSTUB_InferStreamExecRequest) {
@@ -821,7 +823,9 @@ ModelInstanceState::DecoupledMessageQueueMonitor()
             bls_execute,
             (bls_execute->Command() == PYTHONSTUB_InferStreamExecRequest));
       });
-      boost::asio::post(*thread_pool_, std::move(task));
+      std::future<void> future =
+          boost::asio::post(*thread_pool_, std::move(task));
+      futures_.emplace_back(std::move(future));
     }
   }
 }
@@ -1875,14 +1879,12 @@ ModelInstanceState::~ModelInstanceState()
   Stub()->UpdateHealth();
   if (Stub()->IsHealthy()) {
     if (model_state->IsDecoupled()) {
-      // Wait for all the pending tasks to finish.
-      thread_pool_->wait();
+      futures_.clear();
       // Push a dummy message to signal the thread to terminate.
       Stub()->ParentMessageQueue()->Push(DUMMY_MESSAGE);
       decoupled_monitor_.join();
-    } else {
-      thread_pool_->wait();
     }
+    thread_pool_->wait();
   }
   // Terminate stub first to allow any last messages to be received by the back
   // end before deallocating the queue memory