make sure subscribe pulls stay running

nonfree/controller/PubSubListener.cpp

@@ -88,10 +88,11 @@ void PubSubListener::subscribe()
 	while (_run) {
 		try {
 			fprintf(stderr, "PubSubListener::subscribe: starting session for subscription %s\n", _subscription_id.c_str());
+			_lastMessageTime.store(std::chrono::steady_clock::now());
+
 			auto session = _subscriber->Subscribe([this](pubsub::Message const& m, pubsub::AckHandler h) {
+				_lastMessageTime.store(std::chrono::steady_clock::now());
 				try {
-					fprintf(stderr, "PubSubListener callback invoked: subscription=%s message_id=%s ordering_key=%s\n",
-						_subscription_id.c_str(), m.message_id().c_str(), m.ordering_key().c_str());
 					auto provider = opentelemetry::trace::Provider::GetTracerProvider();
 					auto tracer = provider->GetTracer("PubSubListener");
 
@@ -143,19 +144,38 @@ void PubSubListener::subscribe()
 				_hasSession = true;
 			}
 
-			// Block until the session ends (server disconnect, error, or
-			// cancel from destructor).  Do NOT cancel on a timer — cancelling
-			// races with in-flight acks and silently drops messages,
-			// especially with ordering enabled.
-			auto status = _session.get();
+			// Poll the session with a timeout. If no messages have been
+			// received for 60 seconds, assume the pull stream is frozen
+			// and cancel so we can reconnect.  This avoids the old
+			// 10-second blind cancel that raced with in-flight acks.
+			while (_run) {
+				auto result = _session.wait_for(std::chrono::seconds(15));
+				if (result == std::future_status::ready) {
+					break;	// session ended naturally
+				}
+				auto idle = std::chrono::steady_clock::now() - _lastMessageTime.load();
+				if (idle > std::chrono::seconds(60)) {
+					fprintf(stderr, "PubSubListener: no messages for 60s on %s, reconnecting\n",
+						_subscription_id.c_str());
+					_session.cancel();
+					break;
+				}
+			}
 
 			{
 				std::lock_guard<std::mutex> lock(_sessionMutex);
 				_hasSession = false;
 			}
 
-			if (! status.ok()) {
-				fprintf(stderr, "Subscription session ended: %s\n", status.message().c_str());
+			// Retrieve the session status (blocks until cancel or natural end completes)
+			try {
+				auto status = _session.get();
+				if (! status.ok()) {
+					fprintf(stderr, "Subscription session ended: %s\n", status.message().c_str());
+				}
+			}
+			catch (...) {
+				fprintf(stderr, "Subscription session ended with exception on %s\n", _subscription_id.c_str());
 			}
 		}
 		catch (google::cloud::Status const& status) {

nonfree/controller/PubSubListener.hpp

@@ -39,6 +39,7 @@ class PubSubListener : public NotificationListener {
 	std::mutex _sessionMutex;
 	google::cloud::future<google::cloud::Status> _session;
 	bool _hasSession = false;
+	std::atomic<std::chrono::steady_clock::time_point> _lastMessageTime;
 	google::cloud::pubsub_admin::SubscriptionAdminClient _adminClient;
 	google::cloud::pubsub::Subscription* _subscription;
 	std::shared_ptr<google::cloud::pubsub::Subscriber> _subscriber;