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127 lines
4.0 KiB
Plaintext
127 lines
4.0 KiB
Plaintext
zmq_proxy_steerable(3)
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======================
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NAME
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----
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zmq_proxy_steerable - built-in 0MQ proxy with control flow
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SYNOPSIS
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--------
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*int zmq_proxy_steerable (const void '*frontend', const void '*backend',
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const void '*capture', const void '*control');*
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DESCRIPTION
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-----------
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The _zmq_proxy_steerable()_ function starts the built-in 0MQ proxy in the
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current application thread, as _zmq_proxy()_ do. Please, refer to this function
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for the general description and usage. We describe here only the additional
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control flow provided by the socket passed as the fourth argument "control".
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If the control socket is not NULL, the proxy supports control flow. If
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'PAUSE' is received on this socket, the proxy suspends its activities. If
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'RESUME' is received, it goes on. If 'TERMINATE' is received, it terminates
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smoothly. If 'STATISTICS' is received, the proxy will reply on the control socket
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sending a multipart message with 8 frames, each with an unsigned integer 64-bit
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wide that provide in the following order:
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- number of messages received by the frontend socket
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- number of bytes received by the frontend socket
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- number of messages sent out the frontend socket
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- number of bytes sent out the frontend socket
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- number of messages received by the backend socket
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- number of bytes received by the backend socket
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- number of messages sent out the backend socket
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- number of bytes sent out the backend socket
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At start, the proxy runs normally as if zmq_proxy was used.
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If the control socket is NULL, the function behave exactly as if linkzmq:zmq_proxy[3]
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had been called.
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Refer to linkzmq:zmq_socket[3] for a description of the available socket types.
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Refer to linkzmq:zmq_proxy[3] for a description of the zmq_proxy.
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EXAMPLE USAGE
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-------------
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cf zmq_proxy
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RETURN VALUE
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------------
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The _zmq_proxy_steerable()_ function returns 0 if TERMINATE is sent to its
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control socket. Otherwise, it 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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-------
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.Creating a shared queue proxy
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----
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// Create frontend, backend and control 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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void *control = zmq_socket (context, ZMQ_SUB);
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assert (control);
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// Bind 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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assert (zmq_connect (control, "tcp://*:5557") == 0);
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// Subscribe to the control socket since we have chosen SUB here
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assert (zmq_setsockopt (control, ZMQ_SUBSCRIBE, "", 0));
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// Start the queue proxy, which runs until ETERM or "TERMINATE"
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// received on the control socket
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zmq_proxy_steerable (frontend, backend, NULL, control);
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----
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.Set up a controller in another node, process or whatever
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----
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void *control = zmq_socket (context, ZMQ_PUB);
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assert (control);
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assert (zmq_bind (control, "tcp://*:5557") == 0);
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// pause the proxy
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assert (zmq_send (control, "PAUSE", 5, 0) == 0);
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// resume the proxy
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assert (zmq_send (control, "RESUME", 6, 0) == 0);
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// terminate the proxy
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assert (zmq_send (control, "TERMINATE", 9, 0) == 0);
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// check statistics
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assert (zmq_send (control, "STATISTICS", 10, 0) == 0);
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zmq_msg_t stats_msg;
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while (1) {
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assert (zmq_msg_init (&stats_msg) == 0);
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assert (zmq_recvmsg (control, &stats_msg, 0) == sizeof (uint64_t));
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assert (rc == sizeof (uint64_t));
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printf ("Stat: %lu\n", *(unsigned long int *)zmq_msg_data (&stats_msg));
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if (!zmq_msg_get (&stats_msg, ZMQ_MORE))
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break;
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assert (zmq_msg_close (&stats_msg) == 0);
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}
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assert (zmq_msg_close (&stats_msg) == 0);
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---
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SEE ALSO
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--------
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linkzmq:zmq_proxy[3]
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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 page was written by the 0MQ community. To make a change please
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read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.
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