Feat: Delay the resumption of the message queue after reconnect

include/ocpp/common/message_queue.hpp

@@ -94,8 +94,8 @@ template <typename M> class MessageQueue {
     /// message queue for non-transaction related messages
     std::queue<std::shared_ptr<ControlMessage<M>>> normal_message_queue;
     std::shared_ptr<ControlMessage<M>> in_flight;
-    std::mutex message_mutex;
-    std::condition_variable cv;
+    std::recursive_mutex message_mutex;
+    std::condition_variable_any cv;
     std::function<bool(json message)> send_callback;
     std::vector<M> external_notify;
     bool paused;
@@ -107,6 +107,12 @@ template <typename M> class MessageQueue {
     Everest::SteadyTimer in_flight_timeout_timer;
     Everest::SteadyTimer notify_queue_timer;
 
+    // This timer schedules the resumption of the message queue
+    Everest::SteadyTimer resume_timer;
+    // Counts the number of pause()/resume() calls.
+    // Used by the resume timer callback to abort itself in case the timer triggered before it could be cancelled.
+    u_int64_t pause_resume_ctr = 0;
+
     // key is the message id of the stop transaction and the value is the transaction id
     // this map is used for StopTransaction.req that have been put on the message queue without having received a
     // transactionId from the backend (e.g. when offline) it is used to replace the transactionId in the
@@ -147,7 +153,7 @@ template <typename M> class MessageQueue {
     void add_to_normal_message_queue(std::shared_ptr<ControlMessage<M>> message) {
         EVLOG_debug << "Adding message to normal message queue";
         {
-            std::lock_guard<std::mutex> lk(this->message_mutex);
+            std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
             this->normal_message_queue.push(message);
             this->new_message = true;
             this->check_queue_sizes();
@@ -158,7 +164,7 @@ template <typename M> class MessageQueue {
     void add_to_transaction_message_queue(std::shared_ptr<ControlMessage<M>> message) {
         EVLOG_debug << "Adding message to transaction message queue";
         {
-            std::lock_guard<std::mutex> lk(this->message_mutex);
+            std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
             this->transaction_message_queue.push_back(message);
             ocpp::common::DBTransactionMessage db_message{message->message, messagetype_to_string(message->messageType),
                                                           message->message_attempts, message->timestamp,
@@ -241,6 +247,16 @@ template <typename M> class MessageQueue {
         }
     }
 
+    // The public resume() delegates the actual resumption to this method
+    void resume_now(u_int64_t expected_pause_resume_ctr) {
+        std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
+        if (this->pause_resume_ctr == expected_pause_resume_ctr) {
+            this->paused = false;
+            this->cv.notify_one();
+            EVLOG_debug << "resume() notified message queue";
+        }
+    }
+
 public:
     /// \brief Creates a new MessageQueue object with the provided \p configuration and \p send_callback
     MessageQueue(const std::function<bool(json message)>& send_callback, const MessageQueueConfig& config,
@@ -260,8 +276,9 @@ template <typename M> class MessageQueue {
             while (this->running) {
                 EVLOG_debug << "Waiting for a message from the message queue";
 
-                std::unique_lock<std::mutex> lk(this->message_mutex);
+                std::unique_lock<std::recursive_mutex> lk(this->message_mutex);
                 using namespace std::chrono_literals;
+                // It's safe to wait on the cv here because we're guaranteed to only lock this->message_mutex once
                 this->cv.wait(lk, [this]() {
                     return !this->running || (!this->paused && this->new_message && this->in_flight == nullptr);
                 });
@@ -532,7 +549,7 @@ template <typename M> class MessageQueue {
                 // we need to remove Call messages from in_flight if we receive a CallResult OR a CallError
 
                 // TODO(kai): we need to do some error handling in the CallError case
-                std::unique_lock<std::mutex> lk(this->message_mutex);
+                std::unique_lock<std::recursive_mutex> lk(this->message_mutex);
                 if (this->in_flight == nullptr) {
                     EVLOG_error
                         << "Received a CALLRESULT OR CALLERROR without a message in flight, this should not happen";
@@ -594,7 +611,7 @@ template <typename M> class MessageQueue {
 
     /// \brief Handles a message timeout or a CALLERROR. \p enhanced_message_opt is set only in case of CALLERROR
     void handle_timeout_or_callerror(const std::optional<EnhancedMessage<M>>& enhanced_message_opt) {
-        std::lock_guard<std::mutex> lk(this->message_mutex);
+        std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
         EVLOG_warning << "Message timeout or CALLERROR for: " << this->in_flight->messageType << " ("
                       << this->in_flight->uniqueId() << ")";
         if (this->in_flight->isTransactionMessage()) {
@@ -664,28 +681,37 @@ template <typename M> class MessageQueue {
     /// \brief Pauses the message queue
     void pause() {
         EVLOG_debug << "pause()";
-        std::lock_guard<std::mutex> lk(this->message_mutex);
+        std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
+        this->pause_resume_ctr++;
+        this->resume_timer.stop();
         this->paused = true;
         this->cv.notify_one();
         EVLOG_debug << "pause() notified message queue";
     }
 
     /// \brief Resumes the message queue
-    void resume() {
-        EVLOG_debug << "resume()";
-        std::lock_guard<std::mutex> lk(this->message_mutex);
-        this->paused = false;
-        this->cv.notify_one();
-        EVLOG_debug << "resume() notified message queue";
+    void resume(std::chrono::seconds delay_on_reconnect) {
+        EVLOG_debug << "resume() called";
+        std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
+        this->pause_resume_ctr++;
+        // Do not delay if this is the first call to resume(), i.e. this is the initial connection
+        if (this->pause_resume_ctr > 1 && delay_on_reconnect > std::chrono::seconds(0)) {
+            EVLOG_debug << "Delaying message queue resume by " << delay_on_reconnect.count() << " seconds";
+            u_int64_t expected_pause_resume_ctr = this->pause_resume_ctr;
+            this->resume_timer.timeout(
+                [this, expected_pause_resume_ctr] { this->resume_now(expected_pause_resume_ctr); }, delay_on_reconnect);
+        } else {
+            this->resume_now(this->pause_resume_ctr);
+        }
     }
 
     bool is_transaction_message_queue_empty() {
-        std::lock_guard<std::mutex> lk(this->message_mutex);
+        std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
         return this->transaction_message_queue.empty();
     }
 
     bool contains_transaction_messages(const CiString<36> transaction_id) {
-        std::lock_guard<std::mutex> lk(this->message_mutex);
+        std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
         for (const auto control_message : this->transaction_message_queue) {
             if (control_message->messageType == v201::MessageType::TransactionEvent) {
                 v201::TransactionEventRequest req = control_message->message.at(CALL_PAYLOAD);
@@ -698,7 +724,7 @@ template <typename M> class MessageQueue {
     }
 
     bool contains_stop_transaction_message(const int32_t transaction_id) {
-        std::lock_guard<std::mutex> lk(this->message_mutex);
+        std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
         for (const auto control_message : this->transaction_message_queue) {
             if (control_message->messageType == v16::MessageType::StopTransaction) {
                 v16::StopTransactionRequest req = control_message->message.at(CALL_PAYLOAD);
@@ -753,7 +779,7 @@ template <typename M> class MessageQueue {
 
         // replace transaction id in meter values if start_transaction_message_id is present in map
         // this is necessary when the chargepoint queued MeterValue.req for a transaction with unknown transaction_id
-        std::lock_guard<std::mutex> lk(this->message_mutex);
+        std::lock_guard<std::recursive_mutex> lk(this->message_mutex);
         if (this->start_transaction_mid_meter_values_mid_map.count(start_transaction_message_id)) {
             for (auto it = this->transaction_message_queue.begin(); it != transaction_message_queue.end(); ++it) {
                 for (const auto& meter_value_message_id :

include/ocpp/v16/charge_point.hpp

@@ -458,6 +458,10 @@ class ChargePoint {
     /// \param callback
     void register_is_token_reserved_for_connector_callback(
         const std::function<bool(const int32_t connector, const std::string& id_token)>& callback);
+
+    /// \brief Delay draining the message queue after reconnecting, so the CSMS can perform post-reconnect checks first
+    /// \param delay The delay period (seconds)
+    void set_message_queue_resume_delay(std::chrono::seconds delay);
 };
 
 } // namespace v16

include/ocpp/v16/charge_point_impl.hpp

@@ -138,6 +138,9 @@ class ChargePointImpl : ocpp::ChargingStationBase {
     FirmwareStatusEnumType signed_firmware_status;
     int signed_firmware_status_request_id;
 
+    /// \brief optional delay to resumption of message queue after reconnecting to the CSMS
+    std::chrono::seconds message_queue_resume_delay = std::chrono::seconds(0);
+
     // callbacks
     std::function<bool(int32_t connector)> enable_evse_callback;
     std::function<bool(int32_t connector)> disable_evse_callback;
@@ -729,6 +732,12 @@ class ChargePointImpl : ocpp::ChargingStationBase {
     /// \param value
     /// \return Indicates the result of the operation
     ConfigurationStatus set_custom_configuration_key(CiString<50> key, CiString<500> value);
+
+    /// \brief Delay draining the message queue after reconnecting, so the CSMS can perform post-reconnect checks first
+    /// \param delay The delay period (seconds)
+    void set_message_queue_resume_delay(std::chrono::seconds delay) {
+        this->message_queue_resume_delay = delay;
+    }
 };
 
 } // namespace v16

include/ocpp/v201/charge_point.hpp

@@ -226,6 +226,8 @@ class ChargePoint : ocpp::ChargingStationBase {
 
     /// \brief Handler for automatic or explicit OCSP cache updates
     OcspUpdater ocsp_updater;
+    /// \brief optional delay to resumption of message queue after reconnecting to the CSMS
+    std::chrono::seconds message_queue_resume_delay = std::chrono::seconds(0);
 
     bool send(CallError call_error);
 
@@ -643,6 +645,12 @@ class ChargePoint : ocpp::ChargingStationBase {
     /// \return DataTransferResponse contaning the result from CSMS
     DataTransferResponse data_transfer_req(const CiString<255>& vendorId, const std::optional<CiString<50>>& messageId,
                                            const std::optional<std::string>& data);
+
+    /// \brief Delay draining the message queue after reconnecting, so the CSMS can perform post-reconnect checks first
+    /// \param delay The delay period (seconds)
+    void set_message_queue_resume_delay(std::chrono::seconds delay) {
+        this->message_queue_resume_delay = delay;
+    }
 };
 
 } // namespace v201

lib/ocpp/v16/charge_point.cpp

@@ -298,5 +298,9 @@ void ChargePoint::register_is_token_reserved_for_connector_callback(
     this->charge_point->register_is_token_reserved_for_connector_callback(callback);
 }
 
+void ChargePoint::set_message_queue_resume_delay(std::chrono::seconds delay) {
+    this->charge_point->set_message_queue_resume_delay(delay);
+}
+
 } // namespace v16
 } // namespace ocpp

lib/ocpp/v16/charge_point_impl.cpp

@@ -162,14 +162,14 @@ void ChargePointImpl::init_websocket() {
         if (this->connection_state_changed_callback != nullptr) {
             this->connection_state_changed_callback(true);
         }
-        this->message_queue->resume(); //
-        this->connected_callback();    //
+        this->message_queue->resume(this->message_queue_resume_delay);
+        this->connected_callback();
     });
     this->websocket->register_disconnected_callback([this]() {
         if (this->connection_state_changed_callback != nullptr) {
             this->connection_state_changed_callback(false);
         }
-        this->message_queue->pause(); //
+        this->message_queue->pause();
         if (this->ocsp_request_timer != nullptr) {
             this->ocsp_request_timer->stop();
         }

lib/ocpp/v201/charge_point.cpp

@@ -654,7 +654,7 @@ void ChargePoint::init_websocket() {
 
     this->websocket = std::make_unique<Websocket>(connection_options, this->evse_security, this->logging);
     this->websocket->register_connected_callback([this](const int security_profile) {
-        this->message_queue->resume();
+        this->message_queue->resume(this->message_queue_resume_delay);
 
         const auto& security_profile_cv = ControllerComponentVariables::SecurityProfile;
         if (security_profile_cv.variable.has_value()) {