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91 lines
3.1 KiB
Plaintext
91 lines
3.1 KiB
Plaintext
= zmq_proxy(3)
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== NAME
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zmq_proxy - start built-in 0MQ proxy
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== SYNOPSIS
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*int zmq_proxy (void '*frontend', void '*backend', void '*capture');*
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== DESCRIPTION
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The _zmq_proxy()_ function starts the built-in 0MQ proxy in the current
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application thread.
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The proxy connects a frontend socket to a backend socket. Conceptually, data
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flows from frontend to backend. Depending on the socket types, replies may flow
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in the opposite direction. The direction is conceptual only; the proxy is fully
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symmetric and there is no technical difference between frontend and backend.
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Before calling _zmq_proxy()_ you must set any socket options, and connect or
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bind both frontend and backend sockets. The two conventional proxy models are:
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_zmq_proxy()_ runs in the current thread and returns only if/when the current
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context is closed.
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If the capture socket is not NULL, the proxy shall send all messages, received
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on both frontend and backend, to the capture socket. The capture socket should
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be a 'ZMQ_PUB', 'ZMQ_DEALER', 'ZMQ_PUSH', or 'ZMQ_PAIR' socket.
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Refer to xref:zmq_socket.adoc[zmq_socket] for a description of the available socket types.
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== EXAMPLE USAGE
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Shared Queue
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~~~~~~~~~~~~
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When the frontend is a ZMQ_ROUTER socket, and the backend is a ZMQ_DEALER
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socket, the proxy shall act as a shared queue that collects requests from a
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set of clients, and distributes these fairly among a set of services.
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Requests shall be fair-queued from frontend connections and distributed evenly
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across backend connections. Replies shall automatically return to the client
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that made the original request.
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Forwarder
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~~~~~~~~~
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When the frontend is a ZMQ_XSUB socket, and the backend is a ZMQ_XPUB socket,
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the proxy shall act as a message forwarder that collects messages from a set
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of publishers and forwards these to a set of subscribers. This may be used to
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bridge networks transports, e.g. read on tcp:// and forward on pgm://.
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Streamer
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~~~~~~~~
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When the frontend is a ZMQ_PULL socket, and the backend is a ZMQ_PUSH socket,
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the proxy shall collect tasks from a set of clients and forwards these to a set
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of workers using the pipeline pattern.
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== RETURN VALUE
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The _zmq_proxy()_ function always returns `-1` and 'errno' set to *ETERM* or
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*EINTR* (the 0MQ 'context' associated with either of the specified sockets was
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terminated) or *EFAULT* (the provided 'frontend' or 'backend' was invalid).
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== EXAMPLE
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.Creating a shared queue proxy
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----
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// Create frontend and backend sockets
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void *frontend = zmq_socket (context, ZMQ_ROUTER);
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assert (frontend);
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void *backend = zmq_socket (context, ZMQ_DEALER);
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assert (backend);
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// Bind both sockets to TCP ports
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assert (zmq_bind (frontend, "tcp://*:5555") == 0);
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assert (zmq_bind (backend, "tcp://*:5556") == 0);
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// Start the queue proxy, which runs until ETERM
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zmq_proxy (frontend, backend, NULL);
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----
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== SEE ALSO
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* xref:zmq_bind.adoc[zmq_bind]
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* xref:zmq_connect.adoc[zmq_connect]
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* xref:zmq_socket.adoc[zmq_socket]
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* xref:zmq.adoc[zmq]
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== AUTHORS
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This page was written by the 0MQ community. To make a change please
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read the 0MQ Contribution Policy at <https://zeromq.org/how-to-contribute/>.
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