zctx(3)

zctx(3)

CZMQ Manual - CZMQ/3.0.2

Name

zctx - working with ØMQ contexts (deprecated)

Synopsis

//  Create new context, returns context object, replaces zmq_init
CZMQ_EXPORT zctx_t *
    zctx_new (void);

//  Destroy context and all sockets in it, replaces zmq_term
CZMQ_EXPORT void
    zctx_destroy (zctx_t **self_p);

//  Create new shadow context, returns context object
CZMQ_EXPORT zctx_t *
    zctx_shadow (zctx_t *self);
//  Raise default I/O threads from 1, for crazy heavy applications
//  The rule of thumb is one I/O thread per gigabyte of traffic in
//  or out. Call this method before creating any sockets on the context,
//  or calling zctx_shadow, or the setting will have no effect.
CZMQ_EXPORT void
    zctx_set_iothreads (zctx_t *self, int iothreads);

//  Set msecs to flush sockets when closing them, see the ZMQ_LINGER
//  man page section for more details. By default, set to zero, so
//  any in-transit messages are discarded when you destroy a socket or
//  a context.
CZMQ_EXPORT void
    zctx_set_linger (zctx_t *self, int linger);

//  Set initial high-water mark for inter-thread pipe sockets. Note that
//  this setting is separate from the default for normal sockets. You
//  should change the default for pipe sockets *with care*. Too low values
//  will cause blocked threads, and an infinite setting can cause memory
//  exhaustion. The default, no matter the underlying ZeroMQ version, is
//  1,000.
CZMQ_EXPORT void
    zctx_set_pipehwm (zctx_t *self, int pipehwm);

//  Set initial send HWM for all new normal sockets created in context.
//  You can set this per-socket after the socket is created.
//  The default, no matter the underlying ZeroMQ version, is 1,000.
CZMQ_EXPORT void
    zctx_set_sndhwm (zctx_t *self, int sndhwm);

//  Set initial receive HWM for all new normal sockets created in context.
//  You can set this per-socket after the socket is created.
//  The default, no matter the underlying ZeroMQ version, is 1,000.
CZMQ_EXPORT void
    zctx_set_rcvhwm (zctx_t *self, int rcvhwm);

//  Return low-level ØMQ context object, will be NULL before first socket
//  is created. Use with care.
CZMQ_EXPORT void *
    zctx_underlying (zctx_t *self);

//  Self test of this class
CZMQ_EXPORT void
    zctx_test (bool verbose);

Description

The zctx class wraps ØMQ contexts. It manages open sockets in the context and automatically closes these before terminating the context. It provides a simple way to set the linger timeout on sockets, and configure contexts for number of I/O threads. Sets-up signal (interrupt) handling for the process.

The zctx class has these main features:

  • Tracks all open sockets and automatically closes them before calling zmq_term(). This avoids an infinite wait on open sockets.
  • Automatically configures sockets with a ZMQ_LINGER timeout you can define, and which defaults to zero. The default behavior of zctx is therefore like ØMQ/2.0, immediate termination with loss of any pending messages. You can set any linger timeout you like by calling the zctx_set_linger() method.
  • Moves the iothreads configuration to a separate method, so that default usage is 1 I/O thread. Lets you configure this value.
  • Sets up signal (SIGINT and SIGTERM) handling so that blocking calls such as zmq_recv() and zmq_poll() will return when the user presses Ctrl-C.

this class is deprecated in favor of zsock, which does not expose contexts in the API at all. All zsock instances use the same global context.

Example

From zctx_test method

// Create and destroy a context without using it
zctx_t *ctx = zctx_new ();
assert (ctx);
zctx_destroy (&ctx);
assert (ctx == NULL);

// Create a context with many busy sockets, destroy it
ctx = zctx_new ();
assert (ctx);
zctx_set_iothreads (ctx, 1);
zctx_set_linger (ctx, 5); // 5 msecs
void *s1 = zctx__socket_new (ctx, ZMQ_PAIR);
assert (s1);
void *s2 = zctx__socket_new (ctx, ZMQ_XREQ);
assert (s2);
void *s3 = zctx__socket_new (ctx, ZMQ_REQ);
assert (s3);
void *s4 = zctx__socket_new (ctx, ZMQ_REP);
assert (s4);
void *s5 = zctx__socket_new (ctx, ZMQ_PUB);
assert (s5);
void *s6 = zctx__socket_new (ctx, ZMQ_SUB);
assert (s6);
int rc = zsocket_connect (s1, "tcp://127.0.0.1:5555");
assert (rc == 0);
rc = zsocket_connect (s2, "tcp://127.0.0.1:5555");
assert (rc == 0);
rc = zsocket_connect (s3, "tcp://127.0.0.1:5555");
assert (rc == 0);
rc = zsocket_connect (s4, "tcp://127.0.0.1:5555");
assert (rc == 0);
rc = zsocket_connect (s5, "tcp://127.0.0.1:5555");
assert (rc == 0);
rc = zsocket_connect (s6, "tcp://127.0.0.1:5555");
assert (rc == 0);
assert (zctx_underlying (ctx)); zctx_destroy (&ctx);

Authors

The czmq manual was written by the authors in the AUTHORS file.

Resources

Main web site:

Report bugs to the email <gro.qmorez.stsil|ved-qmorez#gro.qmorez.stsil|ved-qmorez>

Copyright

Copyright (c) 1991-2012 iMatix Corporation — http://www.imatix.com Copyright other contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for ØMQ: http://czmq.zeromq.org This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/. LICENSE included with the czmq distribution.