boost搭建的http服务端接收文件失败

Question

请问C++ 使用boost实现http服务端时，在接收form-data中的文件时，
文件超过1mb就会
报错：ec: beast.http:9
message: body limit exceeded
在网上找了几个设置请求体大小的方法没有作用

代码如下：

class http_connection : public std::enable_shared_from_this<http_connection>
{
public:
    http_connection(tcp::socket socket)
        : socket_(std::move(socket))
    {
    
    }

    // Initiate the asynchronous operations associated with the connection.
    void
        start()
    {
    
        read_request();
        check_deadline();
    }

private:
    // The socket for the currently connected client.
    tcp::socket socket_;

    // The buffer for performing reads.
    beast::flat_buffer buffer_;

    // The request message.
    http::request<http::dynamic_body> request_;
    

    // The response message.
    http::response<http::dynamic_body> response_;

    // The timer for putting a deadline on connection processing.
    net::steady_timer deadline_{
        socket_.get_executor(), std::chrono::seconds(60 * 20) };

    // Asynchronously receive a complete request message.
    void read_request()
    {
        auto self = shared_from_this();        
        http::async_read(
            socket_,
            buffer_,
            request_,        
            [self](beast::error_code ec,
                std::size_t bytes_transferred)
            {
                std::cout << "开始读取http接口数据 " << std::endl;
                boost::ignore_unused(bytes_transferred);
                std::cout << "1 " << std::endl;
                if (!ec) {
                    self->process_request();
                    std::cout << "2 " << std::endl;                
                }
                std::cout<< "ec: " << ec << std::endl;
                std::cout<< "message: " << ec.message() << std::endl;
                    
            });
        std::cout << "3 " << std::endl;
    }

    // Determine what needs to be done with the request message.
    void process_request()
    {
        std::cout << "选择接口请求方式 "<< request_.method() << std::endl;
        response_.version(request_.version());
        response_.keep_alive(false);

        switch (request_.method())
        {
        case http::verb::get:
            response_.result(http::status::ok);
            response_.set(http::field::server, "Beast");
            create_response();
            break;
        case http::verb::post:
            response_.result(http::status::ok);
            response_.set(http::field::server, "Beast");
            create_post_response();
            break;
        default:
            // We return responses indicating an error if
            // we do not recognize the request method.
            response_.result(http::status::bad_request);
            response_.set(http::field::content_type, "text/plain");
            beast::ostream(response_.body())
                << "Invalid request-method '"
                << std::string(request_.method_string())
                << "'";
            break;
        }

        write_response();
    }

Answer 1

上午好☀️☀️☀️️
本答案参考ChatGPT-3.5

针对此问题，你可以参考以下方案以解决问题：

1. 使用beast库中的body_limit(std::uint64_t limit)方法设置请求体的大小限制，而非手动读取和检查请求体大小。

2. 检查是否有其它处理程序导致文件上传失败或卡顿，例如IO线程池是否处理缓慢或陷入死循环。

3. 如果以上两个方案均无效，则可以尝试将文档类型设置为multipart/form-data或multipart/mixed，以确保正确地解析请求体。

修改后的代码如下：

注意：在 process_request() 方法中添加了 request_.body_limit(1024*1024)，限制请求体大小为1MB。

class http_connection : public std::enable_shared_from_this<http_connection> { public: http_connection(tcp::socket socket) : socket_(std::move(socket)) {

}

// Initiate the asynchronous operations associated with the connection.
void start()
{

    read_request();
    check_deadline();
}

private: // The socket for the currently connected client. tcp::socket socket_;

// The buffer for performing reads.
beast::flat_buffer buffer_;

// The request message.
http::request<http::dynamic_body> request_;


// The response message.
http::response<http::dynamic_body> response_;

// The timer for putting a deadline on connection processing.
net::steady_timer deadline_{
    socket_.get_executor(), std::chrono::seconds(60 * 20) };

// Asynchronously receive a complete request message.
void read_request()
{
    auto self = shared_from_this();        
    http::async_read(
        socket_,
        buffer_,
        request_,        
        [self](beast::error_code ec,
            std::size_t bytes_transferred)
        {
            std::cout << "开始读取http接口数据 " << std::endl;
            boost::ignore_unused(bytes_transferred);
            std::cout << "1 " << std::endl;
            if (!ec) {
                self->process_request();
                std::cout << "2 " << std::endl;                
            }
            std::cout<< "ec: " << ec << std::endl;
            std::cout<< "message: " << ec.message() << std::endl;
                
        });
    std::cout << "3 " << std::endl;
}

// Determine what needs to be done with the request message.
void process_request()
{
    request_.body_limit(1024*1024);  // 设置请求体大小限制为1MB
    std::cout << "选择接口请求方式 "<< request_.method() << std::endl;
    response_.version(request_.version());
    response_.keep_alive(false);

    switch (request_.method())
    {
    case http::verb::get:
        response_.result(http::status::ok);
        response_.set(http::field::server, "Beast");
        create_response();
        break;
    case http::verb::post:
        response_.result(http::status::ok);
        response_.set(http::field::server, "Beast");
        create_post_response();
        break;
    default:
        // We return responses indicating an error if
        // we do not recognize the request method.
        response_.result(http::status::bad_request);
        response_.set(http::field::content_type, "text/plain");
        beast::ostream(response_.body())
            << "Invalid request-method '"
            << std::string(request_.method_string())
            << "'";
        break;
    }

    write_response();
}

// ... };