Added queue full notification

include/cppkafka/utils/buffered_producer.h

@@ -87,8 +87,15 @@ template <typename BufferType,
           typename Allocator = std::allocator<ConcreteMessageBuilder<BufferType>>>
 class CPPKAFKA_API BufferedProducer {
 public:
-    enum class FlushMethod { Sync,    ///< Empty the buffer and wait for acks from the broker
-                             Async }; ///< Empty the buffer and don't wait for acks
+    enum class FlushMethod {
+        Sync,    ///< Empty the buffer and wait for acks from the broker.
+        Async    ///< Empty the buffer and don't wait for acks.
+    };
+    enum class QueueFullNotification {
+        None,          ///< Don't notify
+        EdgeTriggered, ///< Notify once. Application must call queue_full_trigger_reset() to enable again.
+        EachOccurence  ///< Notify on each occurence.
+    };
     /**
      * Concrete builder
      */
@@ -358,6 +365,25 @@ public:
      * Simple helper to construct a builder object
      */
     Builder make_builder(std::string topic);
+    
+    /**
+     * Set the type of notification when RD_KAFKA_RESP_ERR__QUEUE_FULL is received.
+     *
+     * This will call the error callback for this producer. By default this is set to QueueFullNotification::None.
+     */
+    void set_queue_full_notification(QueueFullNotification notification);
+    
+    /**
+     * Get the queue full notification type.
+     */
+    QueueFullNotification get_queue_full_notification() const;
+    
+    /**
+     * Reset the queue full notification trigger.
+     *
+     * This function has no effect unless QueueFullNotification == EdgeTriggered.
+     */
+    void queue_full_trigger_reset();
 
     /**
      * \brief Sets the message produce failure callback
@@ -505,6 +531,8 @@ private:
     std::atomic<size_t> total_messages_dropped_{0};
     int max_number_retries_{0};
     bool has_internal_data_{false};
+    QueueFullNotification queue_full_notification_{QueueFullNotification::None};
+    bool queue_full_trigger_{true};
 #ifdef KAFKA_TEST_INSTANCE
     TestParameters* test_params_;
 #endif
@@ -798,6 +826,22 @@ BufferedProducer<BufferType, Allocator>::make_builder(std::string topic) {
     return Builder(std::move(topic));
 }
 
+template <typename BufferType, typename Allocator>
+void BufferedProducer<BufferType, Allocator>::set_queue_full_notification(QueueFullNotification notification) {
+    queue_full_notification_ = notification;
+}
+
+template <typename BufferType, typename Allocator>
+typename BufferedProducer<BufferType, Allocator>::QueueFullNotification
+BufferedProducer<BufferType, Allocator>::get_queue_full_notification() const {
+    return queue_full_notification_;
+}
+
+template <typename BufferType, typename Allocator>
+void BufferedProducer<BufferType, Allocator>::queue_full_trigger_reset() {
+    queue_full_trigger_ = true;
+}
+
 template <typename BufferType, typename Allocator>
 void BufferedProducer<BufferType, Allocator>::set_produce_failure_callback(ProduceFailureCallback callback) {
     produce_failure_callback_ = std::move(callback);
@@ -827,6 +871,9 @@ template <typename BufferType, typename Allocator>
 template <typename BuilderType>
 void BufferedProducer<BufferType, Allocator>::produce_message(BuilderType&& builder) {
     using builder_type = typename std::decay<BuilderType>::type;
+    bool queue_full_notify = (queue_full_notification_ == QueueFullNotification::None) ? false :
+                             (queue_full_notification_ == QueueFullNotification::EdgeTriggered) ?
+                             queue_full_trigger_ : true;
     while (true) {
         try {
             MessageInternalGuard<builder_type> internal_guard(const_cast<builder_type&>(builder));
@@ -840,6 +887,13 @@ void BufferedProducer<BufferType, Allocator>::produce_message(BuilderType&& buil
             if (ex.get_error() == RD_KAFKA_RESP_ERR__QUEUE_FULL) {
                 // If the output queue is full, then just poll
                 producer_.poll();
+                // Notify application so it can slow-down production
+                if (queue_full_notify) {
+                    queue_full_notify = queue_full_trigger_ = false; //clear trigger and local state
+                    CallbackInvoker<Configuration::ErrorCallback>
+                        ("error", get_producer().get_configuration().get_error_callback(), &get_producer())
+                        (get_producer(), static_cast<int>(ex.get_error().get_error()), ex.what());
+                }
             }
             else {
                 throw;