1ZMQ_CTX_SET(3) 0MQ Manual ZMQ_CTX_SET(3)
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6 zmq_ctx_set - set context options
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9 int zmq_ctx_set (void *context, int option_name, int option_value);
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12 The zmq_ctx_set() function shall set the option specified by the
13 option_name argument to the value of the option_value argument.
14 The zmq_ctx_set() function accepts the following options:
16 ZMQ_BLOCKY: Fix blocky behavior
18 By default the context will block, forever, on a zmq_ctx_term call. The
19 assumption behind this behavior is that abrupt termination will cause
20 message loss. Most real applications use some form of handshaking to
21 ensure applications receive termination messages, and then terminate
22 the context with ZMQ_LINGER set to zero on all sockets. This setting is
23 an easier way to get the same result. When ZMQ_BLOCKY is set to false,
24 all new sockets are given a linger timeout of zero. You must still
25 close all sockets before calling zmq_ctx_term.
26 Default value true (old behavior)
29 ZMQ_IO_THREADS: Set number of I/O threads
32 The ZMQ_IO_THREADS argument specifies the size of the 0MQ thread pool
33 to handle I/O operations. If your application is using only the inproc
34 transport for messaging you may set this to zero, otherwise set it to
35 at least one. This option only applies before creating any sockets on
36 the context.
37 Default value 1
40 ZMQ_THREAD_SCHED_POLICY: Set scheduling policy for I/O threads
43 The ZMQ_THREAD_SCHED_POLICY argument sets the scheduling policy for
44 internal context’s thread pool. This option is not available on
45 windows. Supported values for this option can be found in sched.h file,
46 or at http://man7.org/linux/man-pages/man2/sched_setscheduler.2.html.
47 This option only applies before creating any sockets on the context.
48 Default value -1
51 ZMQ_THREAD_PRIORITY: Set scheduling priority for I/O threads
54 The ZMQ_THREAD_PRIORITY argument sets scheduling priority for internal
55 context’s thread pool. This option is not available on windows.
56 Supported values for this option depend on chosen scheduling policy. On
57 Linux, when the scheduler policy is SCHED_OTHER, SCHED_IDLE or
58 SCHED_BATCH, the OS scheduler will not use the thread priority but
59 rather the thread "nice value"; in such cases the system call "nice"
60 will be used to set the nice value to -20 (max priority) instead of
61 adjusting the thread priority (which must be zero for those scheduling
62 policies). Details can be found in sched.h file, or at
63 http://man7.org/linux/man-pages/man2/sched_setscheduler.2.html. This
64 option only applies before creating any sockets on the context.
65 Default value -1
69 ZMQ_THREAD_AFFINITY_CPU_ADD: Add a CPU to list of affinity for I/O threads
72 The ZMQ_THREAD_AFFINITY_CPU_ADD argument adds a specific CPU to the
73 affinity list for the internal context’s thread pool. This option is
74 only supported on Linux. This option only applies before creating any
75 sockets on the context. The default affinity list is empty and means
76 that no explicit CPU-affinity will be set on internal context’s
77 threads.
78 Default value -1
81 ZMQ_THREAD_AFFINITY_CPU_REMOVE: Remove a CPU to list of affinity for I/O
84 threads
85 The ZMQ_THREAD_AFFINITY_CPU_REMOVE argument removes a specific CPU to
86 the affinity list for the internal context’s thread pool. This option
87 is only supported on Linux. This option only applies before creating
88 any sockets on the context. The default affinity list is empty and
89 means that no explicit CPU-affinity will be set on internal context’s
90 threads.
91 Default value -1
94 ZMQ_THREAD_NAME_PREFIX: Set name prefix for I/O threads
97 The ZMQ_THREAD_NAME_PREFIX argument sets a numeric prefix to each
98 thread created for the internal context’s thread pool. This option is
99 only supported on Linux. This option is useful to help debugging done
100 via "top -H" or "gdb"; in case multiple processes on the system are
101 using ZeroMQ it is useful to provide through this context option an
102 application-specific prefix to distinguish ZeroMQ background threads
103 that belong to different processes. This option only applies before
104 creating any sockets on the context.
105 Default value -1
108 ZMQ_MAX_MSGSZ: Set maximum message size
111 The ZMQ_MAX_MSGSZ argument sets the maximum allowed size of a message
112 sent in the context. You can query the maximal allowed value with
113 zmq_ctx_get(3) using the ZMQ_MAX_MSGSZ option.
114 Default value INT_MAX
117 Maximum value INT_MAX
119 ZMQ_ZERO_COPY_RECV: Specify message decoding strategy
122 The ZMQ_ZERO_COPY_RECV argument specifies whether the message decoder
123 should use a zero copy strategy when receiving messages. The zero copy
124 strategy can lead to increased memory usage in some cases. This option
125 allows you to use the older copying strategy. You can query the value
126 of this option with zmq_ctx_get(3) using the ZMQ_ZERO_COPY_RECV option.
127 NOTE: in DRAFT state, not yet available in stable releases.
128 Default value 1
131 ZMQ_MAX_SOCKETS: Set maximum number of sockets
134 The ZMQ_MAX_SOCKETS argument sets the maximum number of sockets allowed
135 on the context. You can query the maximal allowed value with
136 zmq_ctx_get(3) using the ZMQ_SOCKET_LIMIT option.
137 Default value 1023
140 ZMQ_IPV6: Set IPv6 option
143 The ZMQ_IPV6 argument sets the IPv6 value for all sockets created in
144 the context from this point onwards. A value of 1 means IPv6 is
145 enabled, while 0 means the socket will use only IPv4. When IPv6 is
146 enabled, a socket will connect to, or accept connections from, both
147 IPv4 and IPv6 hosts.
148 Default value 0
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154 The zmq_ctx_set() function returns zero if successful. Otherwise it
155 returns -1 and sets errno to one of the values defined below.
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158 EINVAL
159 The requested option option_name is unknown.
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162 Setting a limit on the number of sockets.
163 void *context = zmq_ctx_new ();
165 zmq_ctx_set (context, ZMQ_MAX_SOCKETS, 256);
166 int max_sockets = zmq_ctx_get (context, ZMQ_MAX_SOCKETS);
167 assert (max_sockets == 256);
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171 zmq_ctx_get(3) zmq(7)
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174 This page was written by the 0MQ community. To make a change please
175 read the 0MQ Contribution Policy at
176 http://www.zeromq.org/docs:contributing.
1770MQ 4.3.4 01/22/2022 ZMQ_CTX_SET(3)