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9ac40c47d7
- reverted commit 941be8d217.
- fixed zmq_device implementation for latest socket_base class
- added back zmq_device.3 man page
126 lines
4.0 KiB
Plaintext
126 lines
4.0 KiB
Plaintext
zmq_device(3)
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=============
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NAME
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----
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zmq_device - start built-in 0MQ device
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SYNOPSIS
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--------
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*int zmq_device (int 'device', const void '*frontend', const void '*backend');*
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DESCRIPTION
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-----------
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The _zmq_device()_ function starts a built-in 0MQ device. The 'device' argument
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is one of:
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'ZMQ_QUEUE'::
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starts a queue device
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'ZMQ_FORWARDER'::
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starts a forwarder device
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'ZMQ_STREAMER'::
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starts a streamer device
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The device 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.
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Before calling _zmq_device()_ you must set any socket options, and connect or
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bind both frontend and backend sockets. The two conventional device models are:
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*proxy*::
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bind frontend socket to an endpoint, and connect backend socket to
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downstream components. A proxy device model does not require changes to
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the downstream topology but that topology is static (any changes require
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reconfiguring the device).
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*broker*::
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bind frontend socket to one endpoint and bind backend socket to a second
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endpoint. Downstream components must now connect into the device. A broker
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device model allows a dynamic downstream topology (components can come and
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go at any time).
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_zmq_device()_ runs in the current thread and returns only if/when the current
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context is closed.
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QUEUE DEVICE
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------------
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'ZMQ_QUEUE' creates a shared queue that collects requests from a set of clients,
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and distributes these fairly among a set of services. Requests are fair-queued
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from frontend connections and load-balanced between backend connections.
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Replies automatically return to the client that made the original request.
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This device is part of the 'request-reply' pattern. The frontend speaks to
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clients and the backend speaks to services. You should use 'ZMQ_QUEUE' with a
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'ZMQ_ROUTER' socket for the frontend and a 'ZMQ_DEALER' socket for the backend.
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Other combinations are not documented.
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Refer to linkzmq:zmq_socket[3] for a description of these socket types.
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FORWARDER DEVICE
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----------------
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'ZMQ_FORWARDER' collects messages from a set of publishers and forwards these to
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a set of subscribers. You will generally use this to bridge networks, e.g. read
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on TCP unicast and forward on multicast.
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This device is part of the 'publish-subscribe' pattern. The frontend speaks to
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publishers and the backend speaks to subscribers. You should use
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'ZMQ_FORWARDER' with a 'ZMQ_SUB' socket for the frontend and a 'ZMQ_PUB' socket
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for the backend. Other combinations are not documented.
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Refer to linkzmq:zmq_socket[3] for a description of these socket types.
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STREAMER DEVICE
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---------------
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'ZMQ_STREAMER' collects tasks from a set of pushers and forwards these to a set
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of pullers. You will generally use this to bridge networks. Messages are
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fair-queued from pushers and load-balanced to pullers.
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This device is part of the 'pipeline' pattern. The frontend speaks to pushers
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and the backend speaks to pullers. You should use 'ZMQ_STREAMER' with a
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'ZMQ_PULL' socket for the frontend and a 'ZMQ_PUSH' socket for the backend.
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Other combinations are not documented.
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Refer to linkzmq:zmq_socket[3] for a description of these socket types.
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RETURN VALUE
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------------
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The _zmq_device()_ function always returns `-1` and 'errno' set to *ETERM* (the
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0MQ 'context' associated with either of the specified sockets was terminated).
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EXAMPLE
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-------
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.Creating a queue broker
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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 (backend);
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void *backend = zmq_socket (context, ZMQ_DEALER);
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assert (frontend);
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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 a queue device
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zmq_device (ZMQ_QUEUE, frontend, backend);
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----
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SEE ALSO
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--------
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linkzmq:zmq_bind[3]
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linkzmq:zmq_connect[3]
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linkzmq:zmq_socket[3]
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linkzmq:zmq[7]
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AUTHORS
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-------
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This 0MQ manual page was written by Pieter Hintjens <ph@imatix.com>
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