About the code implementation of qos0 message cache

[jiang4869]

Hello, about mosquitto code implementation, have a question want to ask.

As described in the configuration file, qos0 messages are cached only when queue_qos0_message is set to true and max_queued_message is set to 0.

I would like to ask whether the implementation code of this function is in the function db_message_insert in src/databases. When the socket is invalid, check whether the qos0 message is cached.

So when can a socket be invalid? Does the socket become invalid if the subscriber consumes more than the broker can push it?

int db__message_insert(struct mosquitto *context, uint16_t mid, enum mosquitto_msg_direction dir, uint8_t qos, bool retain, struct mosquitto_msg_store *stored, mosquitto_property *properties, bool update) {
	......
	if(context->sock == INVALID_SOCKET){
		/* Client is not connected only queue messages with QoS>0. */
		if(qos == 0 && !db.config->queue_qos0_messages){
			if(!context->bridge){
				mosquitto_property_free_all(&properties);
				return 2;
			}else{
				if(context->bridge->start_type != bst_lazy){
					mosquitto_property_free_all(&properties);
					return 2;
				}
			}
		}
		if(context->bridge && context->bridge->clean_start_local == true){
			mosquitto_property_free_all(&properties);
			return 2;
		}
	}
	......
	if(context->sock != INVALID_SOCKET){
		.......
	}else{
		if (db__ready_for_queue(context, qos, msg_data)){
			state = mosq_ms_queued;
		}else{
			G_MSGS_DROPPED_INC();
			if(context->is_dropping == false){
				context->is_dropping = true;
				log__printf(NULL, MOSQ_LOG_NOTICE,
						"Outgoing messages are being dropped for client %s.",
						context->id);
			}
			mosquitto_property_free_all(&properties);
			return 2;
		}
	}
}

Thank you for answering my question in your busy schedule.