Allow to get the size of the queue.

examples/file_downloader.cc

@@ -31,7 +31,6 @@ int main(int argc, char* argv[]) {
     if (auto file_body = r->file_body()) {
       file_body->Move(path);
     }
-
   } catch (const std::exception& e) {
     std::cerr << e.what() << std::endl;
   }

webcc/queue.h

@@ -54,9 +54,14 @@ public:
     not_empty_cv_.notify_one();
   }
 
+  std::size_t Size() const {
+    std::lock_guard<std::mutex> lock(mutex_);
+    return message_list_.size();
+  }
+
 private:
   std::list<T> message_list_;
-  std::mutex mutex_;
+  mutable std::mutex mutex_;
   std::condition_variable not_empty_cv_;
 };
 

webcc/server.cc

@@ -250,10 +250,13 @@ void Server::WorkerRoutine() {
 void Server::StopWorkers() {
   LOG_INFO("Stopping workers...");
 
-  // Clear pending connections.
+  // Clear/drop pending connections.
-  // The connections will be closed later.
+  // The connections will be closed later (see DoStop).
-  LOG_INFO("Clear pending connections...");
+  // Alternatively, we can wait for the pending connections to be handled.
-  queue_.Clear();
+  if (queue_.Size() != 0) {
+    LOG_INFO("Clear pending connections...");
+    queue_.Clear();
+  }
 
   // Enqueue a null connection to trigger the first worker to stop.
   queue_.Push(ConnectionPtr());