問題描述

我有一個使用 ZeroMQ 進行消息傳遞的 C++ 應用程序.但它還必須為基于 AJAX/Comet 的 Web 服務提供 SGCI 連接.

I've got a C++ application that is using ZeroMQ for some messaging. But it also has to provide a SGCI connection for an AJAX / Comet based web service.

為此，我需要一個普通的 TCP 套接字.我可以通過普通的 Posix 套接字做到這一點，但為了保持跨平臺的便攜性并使我的生活更輕松(我希望......)我正在考慮使用 Boost::ASIO.

For this I need a normal TCP socket. I could do that by normal Posix sockets, but to stay cross platform portable and make my life easier (I hope...) I was thinking of using Boost::ASIO.

但現(xiàn)在我有 ZMQ 的沖突，想要使用它自己的 zmq_poll() 和 ASIO 它是 io_service.run()...

But now I have the clash of ZMQ wanting to use it's own zmq_poll() and ASIO it's io_service.run()...

有沒有辦法讓 ASIO 與 0MQ zmq_poll() 一起工作?

Is there a way to get ASIO to work together with the 0MQ zmq_poll()?

或者是否有其他推薦的方法來實現(xiàn)這樣的設(shè)置?

Or is there an other recommended way to achieve such a setup?

注意:我可以通過使用多線程來解決這個問題——但它只是一個小小的單核/CPU 盒子，它可以以非常低的 SCGI 流量運行該程序，所以多線程會浪費資源......

Note: I could solve that by using multiple threads - but it's only a little single core / CPU box that'll run that program with a very low amount of SCGI traffic, so multithreading would be a waste of resources...

推薦答案

閱讀文檔后 這里和這里，特別是這一段

After reading the documentation here and here, specifically this paragraph

ZMQ_FD:檢索與套接字關(guān)聯(lián)的文件描述符 ZMQ_FD選項應檢索與關(guān)聯(lián)的文件描述符指定的套接字.返回的文件描述符可用于將套接字集成到現(xiàn)有的事件循環(huán)中；?MQ 庫應以邊緣觸發(fā)的方式向套接字上的任何未決事件發(fā)出信號通過使文件描述符準備好讀取來實現(xiàn)時尚.

ZMQ_FD: Retrieve file descriptor associated with the socket The ZMQ_FD option shall retrieve the file descriptor associated with the specified socket. The returned file descriptor can be used to integrate the socket into an existing event loop; the ?MQ library shall signal any pending events on the socket in an edge-triggered fashion by making the file descriptor become ready for reading.

我認為您可以為每個 zmq_pollitem_t 使用 null_buffers并將事件循環(huán)推遲到 io_service，完全繞過 zmq_poll().然而，上述文檔中似乎有一些警告，特別是

I think you can use null_buffers for every zmq_pollitem_t and defer the event loop to an io_service, completely bypassing zmq_poll() altogether. There appear to be some caveats in the aforementioned documentation however, notably

從返回的文件描述符中讀取的能力不必然表明消息可供讀取，或可以寫入，底層套接字；應用程序必須檢索實際事件狀態(tài)，隨后檢索 ZMQ_EVENTS選項.

The ability to read from the returned file descriptor does not necessarily indicate that messages are available to be read from, or can be written to, the underlying socket; applications must retrieve the actual event state with a subsequent retrieval of the ZMQ_EVENTS option.

因此，當您的一個 zmq 套接字的處理程序被觸發(fā)時，您必須在處理我認為的事件之前做更多的工作.未編譯的偽代碼如下

So when the handler for one of your zmq sockets is fired, you'll have to do a little more work before handling the event I think. Uncompiled pseudo-code is below

const int fd = getZmqDescriptorSomehow();
boost::asio::posix::stream_descriptor socket( _io_service, fd );
socket->async_read_some(
    boost::asio::null_buffers(),
    [=](const boost::system::error_code& error)
    {
       if (!error) {
           // handle data ready to be read
       }
     }
);

注意你不必在這里使用 lambda，boost::bind 到成員函數(shù)就足夠了.

note you don't have to use a lambda here, boost::bind to a member function would be sufficient.

這篇關(guān)于將 ZeroMQ 與 Boost::ASIO 一起使用的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！