Libmosquitto publish 不会将所有消息传递到 Azure IoT Hub

我正在尝试每秒向 Azure IoT 中心内置事件中心发布 100 多条消息。我正在使用libmosquitto 1.6.8库。我使用的是 Azure IoT 中心的免费层包，我知道每秒有 100 条消息的限制。但这与这个问题无关。我甚至无法将一半的消息发布到 AZ IoT 中心。

基本上，我有一个需要发送的多映射中多个值的列表。指标列表：

std::multimap< const std::string, std::tuple< const std::string, const std::string, float> > calculatedMetricList;

我将遍历多重映射并将每个值构造为对象有效负载，并将其发送。这意味着 mosquitto_publish 方法将被多次调用。

以下是用于发布消息的代码：

void MosquittoClient::sendDataToUpstreamSystem(){
StatisticalMethod statisticalMethod;
int rc;
MosquittoClient pub_mosq(
"<IoT Hub Name>.azure-devices.net",
"<deviceID>", 
"<username>", 
"<Password>", 
"devices/<deviceID>/messages/events/");
printf("Using MQTT to get data payload from host: %s and on port: %d.rn", pub_mosq.get_host(), pub_mosq.get_port());
// init the mosquitto lib
mosquitto_lib_init();
// create the mosquito object
struct mosquitto* mosq = mosquitto_new(pub_mosq.get_deviceID(), false, NULL);
// add callback functions
mosquitto_connect_callback_set(mosq, MosquittoClient::connect_callback);
mosquitto_publish_callback_set(mosq, MosquittoClient::publish_callback);
mosquitto_message_callback_set(mosq, MosquittoClient::on_message);
mosquitto_disconnect_callback_set(mosq, MosquittoClient::on_disconnect_callback);
// set mosquitto username, password and options
mosquitto_username_pw_set(mosq, pub_mosq.get_userName(), pub_mosq.get_password());
// specify the certificate to use
std::ifstream infile(pub_mosq.get_certificate());
bool certExists = infile.good();
infile.close();
if (!certExists)
{
printf("Warning: Could not find file '%s'! The mosquitto loop may fail.rn", pub_mosq.get_certificate());
}
printf("Using certificate: %srn", pub_mosq.get_certificate());
mosquitto_tls_set(mosq, pub_mosq.get_certificate(), NULL, NULL, NULL, NULL);
// specify the mqtt version to use
int* option = new int(MQTT_PROTOCOL_V311);
rc = mosquitto_opts_set(mosq, MOSQ_OPT_PROTOCOL_VERSION, option);
if (rc != MOSQ_ERR_SUCCESS)
{
rc = pub_mosq.mosquitto_error(rc, "Error: opts_set protocol version");
}
else
{
printf("Setting up options OKrn");
}
// connect
printf("Connecting...rn");
rc = mosquitto_connect_async(mosq, pub_mosq.get_host(), pub_mosq.get_port(), 4);
if (rc != MOSQ_ERR_SUCCESS)
{
rc = pub_mosq.mosquitto_error(rc, NULL);
}
else
{
printf("Connect returned OKrn");
rc = mosquitto_loop_start(mosq);
if (rc != MOSQ_ERR_SUCCESS)
{
rc = pub_mosq.mosquitto_error(rc, NULL);
}
else
{
do
{
for (auto itr = Metrics::calculatedMetricList.begin(); itr != Metrics::calculatedMetricList.end(); itr++) { 
int msgId = rand();
std::string test1= itr->first;
std::string test2 = std::get<0>(itr->second);
std::string test3= std::get<1>(itr->second); // metric type 
float value = std::get<2>(itr->second); // value
DataPayload objectPayload(
75162345,
496523,
test3,
value,
"test",
test1,
"test",
"test",
123,
213,
23
);
objectPayload.setPayload();
std::string dataPayload = objectPayload.getPayload();
//DEBUG
std::cout << "dataPayload: " << dataPayload << std::endl;
//DEBUG
std::cout << "dataPayload Size: " << dataPayload.size() << std::endl;
// once connected, we can publish (send) a Telemetry message
printf("Publishing to topic: %srn", pub_mosq.get_topic());
rc = pub_mosq.publishToTopic(mosq, &msgId, dataPayload.size(), (char *)dataPayload.c_str());
if (rc == MOSQ_ERR_SUCCESS)
{
printf("Publish returned OKrn");
}
else 
{               
rc = pub_mosq.mosquitto_error(rc, NULL);
}
} 
} while (rc != MOSQ_ERR_SUCCESS);   
}
}
mosquitto_loop_stop(mosq, true);
mosquitto_destroy(mosq);
mosquitto_lib_cleanup();}

发布方法：

int MosquittoClient::publishToTopic(struct mosquitto *mosq, int *msgId, int sizeOfData, char *data)
{
return mosquitto_publish(mosq, msgId, p_topic, sizeOfData, data, 1, true);
}

根据控制台，运行程序时，发布的所有消息都返回正常。但只有一两条消息出现在 Azure IoT 中心端。

下图显示了对 IoT 中心的监视，当时只有一条消息通过。 设备资源管理器孪生监视

我已经尝试了许多不同的解决方案，但该程序无法发布所有消息。看起来发布方法正在等待完成第一条消息，但迭代正在移动到下一条消息，导致它被删除。如果这是丢弃消息的原因，那么对消息发送进行排序的最佳方法是什么？否则，还有什么可能导致邮件被丢弃？

更新

问题是程序没有等到消息成功发布到代理(Azure IoT 中心(。如果返回publish_callback，您将知道消息是否已成功发布到代理。

void MosquittoClient::publish_callback(struct mosquitto* mosq, void* userdata, int mid)
{
printf("Publish OK.rn");
}

解决方案是在销毁之前休眠线程，清理调用并在建立连接之前启动 Mosquitto 循环。

sleep(30);
mosquitto_loop_stop(mosq, true);
mosquitto_destroy(mosq);
mosquitto_lib_cleanup();