ZMQ_PROXY_STEERABLE(3) 0MQ Manual ZMQ_PROXY_STEERABLE(3)
NAME
zmq_proxy_steerable - built-in 0MQ proxy with control flow
SYNOPSIS
int zmq_proxy_steerable (const void *frontend, const void *backend,
const void *capture, const void *control);
DESCRIPTION
The zmq_proxy_steerable() function starts the built-in 0MQ proxy in the
current application thread, as zmq_proxy() do. Please, refer to this
function for the general description and usage. We describe here only
the additional control flow provided by the socket passed as the fourth
argument "control".
If the control socket is not NULL, the proxy supports control flow. If
PAUSE is received on this socket, the proxy suspends its activities. If
RESUME is received, it goes on. If TERMINATE is received, it terminates
smoothly. If STATISTICS is received, the proxy will reply on the
control socket sending a multipart message with 8 frames, each with an
unsigned integer 64-bit wide that provide in the following order: -
number of messages received by the frontend socket - number of bytes
received by the frontend socket - number of messages sent out the
frontend socket - number of bytes sent out the frontend socket - number
of messages received by the backend socket - number of bytes received
by the backend socket - number of messages sent out the backend socket
- number of bytes sent out the backend socket
At start, the proxy runs normally as if zmq_proxy was used.
If the control socket is NULL, the function behave exactly as if
zmq_proxy(3) had been called.
Refer to zmq_socket(3) for a description of the available socket types.
Refer to zmq_proxy(3) for a description of the zmq_proxy.
EXAMPLE USAGE
cf zmq_proxy
RETURN VALUE
The zmq_proxy_steerable() function returns 0 if TERMINATE is sent to
its control socket. Otherwise, it returns -1 and errno set to ETERM or
EINTR (the 0MQ context associated with either of the specified sockets
was terminated) or EFAULT (the provided frontend or backend was
invalid).
EXAMPLE
Creating a shared queue proxy.
// Create frontend, backend and control sockets
void *frontend = zmq_socket (context, ZMQ_ROUTER);
assert (frontend);
void *backend = zmq_socket (context, ZMQ_DEALER);
assert (backend);
void *control = zmq_socket (context, ZMQ_SUB);
assert (control);
// Bind sockets to TCP ports
assert (zmq_bind (frontend, "tcp://*:5555") == 0);
assert (zmq_bind (backend, "tcp://*:5556") == 0);
assert (zmq_connect (control, "tcp://*:5557") == 0);
// Subscribe to the control socket since we have chosen SUB here
assert (zmq_setsockopt (control, ZMQ_SUBSCRIBE, "", 0));
// Start the queue proxy, which runs until ETERM or "TERMINATE"
// received on the control socket
zmq_proxy_steerable (frontend, backend, NULL, control);
Set up a controller in another node, process or whatever.
void *control = zmq_socket (context, ZMQ_PUB);
assert (control);
assert (zmq_bind (control, "tcp://*:5557") == 0);
// pause the proxy
assert (zmq_send (control, "PAUSE", 5, 0) == 0);
// resume the proxy
assert (zmq_send (control, "RESUME", 6, 0) == 0);
// terminate the proxy
assert (zmq_send (control, "TERMINATE", 9, 0) == 0);
// check statistics
assert (zmq_send (control, "STATISTICS", 10, 0) == 0);
zmq_msg_t stats_msg;
while (1) {
assert (zmq_msg_init (&stats_msg) == 0);
assert (zmq_recvmsg (control, &stats_msg, 0) == sizeof (uint64_t));
assert (rc == sizeof (uint64_t));
printf ("Stat: %lu\n", *(unsigned long int *)zmq_msg_data (&stats_msg));
if (!zmq_msg_get (&stats_msg, ZMQ_MORE))
break;
assert (zmq_msg_close (&stats_msg) == 0);
}
assert (zmq_msg_close (&stats_msg) == 0);
---
SEE ALSO
zmq_proxy(3) zmq_bind(3) zmq_connect(3) zmq_socket(3) zmq(7)
AUTHORS
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0MQ 4.3.4 01/18/2023 ZMQ_PROXY_STEERABLE(3)
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