AMQP-CPP 初学者问题答案

【问题标题】：AMQP-CPP beginner problemsAMQP-CPP 初学者问题
【发布时间】：2020-11-16 18:02:06
【问题描述】：

我是 rabbitmq 的新手，并尝试让一个侦听器从消息队列中读取。服务器应该没问题（不是我实现的，我猜是用 Java 实现的）。我为消费者使用 C++，并使用 amqpcpp 库。

这是我到目前为止所尝试的：

    int main(int argc, char* const argv[])
{
  // access to the boost asio handler
    // note: we suggest use of 2 threads - normally one is fin (we are simply demonstrating thread safety).
    boost::asio::io_service service(2);

    // handler for libev
    AMQP::LibBoostAsioHandler handler(service);
    
    // make a connection
    AMQP::Address address("amqp://10.40.216.87");
    AMQP::TcpConnection connection(&handler, address);

    // we need a channel too
    AMQP::TcpChannel channel(&connection);


    //channel.onError(errorTCP);

    channel.declareQueue("logmessages");

   // Define callbacks and start
    auto messageCb = [&channel](
            const AMQP::Message &message, uint64_t deliveryTag, 
            bool redelivered)
    {
        std::cout << "message received" << std::endl;
        // acknowledge the message
        // channel.ack(deliveryTag);
        //processMessage(message.routingKey(), message.body());
    };

    // callback function that is called when the consume operation starts
    auto startCb = [](const std::string &consumertag) {

        std::cout << "consume operation started: " << consumertag << std::endl;
    };

    // callback function that is called when the consume operation failed
    auto errorCb = [](const char* message) {

        std::cout << "consume operation failed:" << *message << std::endl;
    };

    channel.consume("logmessages")
        .onReceived(messageCb)
        .onSuccess(startCb)
        .onError(errorCb);

    
    // create a temporary queue
    /*channel.declareQueue(AMQP::exclusive).onSuccess([&connection](const std::string &name, uint32_t messagecount, uint32_t consumercount) {
        
        // report the name of the temporary queue
        std::cout << "declared queue " << name << std::endl;
        
        // now we can close the connection
        connection.close();
    });*/

    channel.consume("devices.state.*");
    
    // run the handler
    // a t the moment, one will need SIGINT to stop.  In time, should add signal handling through boost API.
    return service.run();
}

我总是收到“消费操作失败”。现在的问题是为什么......有没有办法获得更多的错误信息？（例如无法连接 TCP 套接字、找不到正确名称的队列等）。

感谢您的提示！

【问题讨论】：

标签： c++ rabbitmq amqp

【解决方案1】：

在您的代码中，您试图计算 *message 指针而不是消息本身。

而不是，

auto errorCb = [](const char* message) {
    std::cout << "consume operation failed:" << *message << std::endl;
};

应该是，

auto errorCb = [](const char* message) {
    std::cout << "consume operation failed:" << message << std::endl;
};

这应该会给你正确的错误信息。请查看official repo 中的文档/示例。

【讨论】：