NAME¶
zmq_setsockopt - set 0MQ socket options
SYNOPSIS¶
int zmq_setsockopt (void *socket, int
option_name , const void
*option_value, size_t
option_len);
Caution: All options, with the exception of ZMQ_SUBSCRIBE, ZMQ_UNSUBSCRIBE and
ZMQ_LINGER, only take effect for subsequent socket bind/connects.
DESCRIPTION¶
The
zmq_setsockopt() function shall set the option specified by the
option_name argument to the value pointed to by the
option_value
argument for the 0MQ socket pointed to by the
socket argument. The
option_len argument is the size of the option value in bytes.
The following socket options can be set with the
zmq_setsockopt()
function:
ZMQ_HWM: Set high water mark¶
The
ZMQ_HWM option shall set the high water mark for the specified
socket. The high water mark is a hard limit on the maximum number of
outstanding messages 0MQ shall queue in memory for any single peer that the
specified
socket is communicating with.
If this limit has been reached the socket shall enter an exceptional state and
depending on the socket type, 0MQ shall take appropriate action such as
blocking or dropping sent messages. Refer to the individual socket
descriptions in
zmq_socket(3) for details on the exact action taken for
each socket type.
The default
ZMQ_HWM value of zero means "no limit".
Option value type |
uint64_t |
Option value unit |
messages |
Default value |
0 |
Applicable socket types |
all |
ZMQ_SWAP: Set disk offload size¶
The
ZMQ_SWAP option shall set the disk offload (swap) size for the
specified
socket. A socket which has
ZMQ_SWAP set to a non-zero
value may exceed its high water mark; in this case outstanding messages shall
be offloaded to storage on disk rather than held in memory.
The value of
ZMQ_SWAP defines the maximum size of the swap space in
bytes.
Option value type |
int64_t |
Option value unit |
bytes |
Default value |
0 |
Applicable socket types |
all |
ZMQ_AFFINITY: Set I/O thread affinity¶
The
ZMQ_AFFINITY option shall set the I/O thread affinity for newly
created connections on the specified
socket.
Affinity determines which threads from the 0MQ I/O thread pool associated with
the socket’s
context shall handle newly created connections. A
value of zero specifies no affinity, meaning that work shall be distributed
fairly among all 0MQ I/O threads in the thread pool. For non-zero values, the
lowest bit corresponds to thread 1, second lowest bit to thread 2 and so on.
For example, a value of 3 specifies that subsequent connections on
socket shall be handled exclusively by I/O threads 1 and 2.
See also
zmq_init(3) for details on allocating the number of I/O threads
for a specific
context.
Option value type |
uint64_t |
Option value unit |
N/A (bitmap) |
Default value |
0 |
Applicable socket types |
N/A |
ZMQ_IDENTITY: Set socket identity¶
The
ZMQ_IDENTITY option shall set the identity of the specified
socket. Socket identity determines if existing 0MQ infrastructure (
message queues,
forwarding devices) shall be identified with a
specific application and persist across multiple runs of the application.
If the socket has no identity, each run of an application is completely separate
from other runs. However, with identity set the socket shall re-use any
existing 0MQ infrastructure configured by the previous run(s). Thus the
application may receive messages that were sent in the meantime,
message
queue limits shall be shared with previous run(s) and so on.
Identity should be at least one byte and at most 255 bytes long. Identities
starting with binary zero are reserved for use by 0MQ infrastructure.
Option value type |
binary data |
Option value unit |
N/A |
Default value |
NULL |
Applicable socket types |
all |
ZMQ_SUBSCRIBE: Establish message filter¶
The
ZMQ_SUBSCRIBE option shall establish a new message filter on a
ZMQ_SUB socket. Newly created
ZMQ_SUB sockets shall filter out
all incoming messages, therefore you should call this option to establish an
initial message filter.
An empty
option_value of length zero shall subscribe to all incoming
messages. A non-empty
option_value shall subscribe to all messages
beginning with the specified prefix. Multiple filters may be attached to a
single
ZMQ_SUB socket, in which case a message shall be accepted if it
matches at least one filter.
Option value type |
binary data |
Option value unit |
N/A |
Default value |
N/A |
Applicable socket types |
ZMQ_SUB |
ZMQ_UNSUBSCRIBE: Remove message filter¶
The
ZMQ_UNSUBSCRIBE option shall remove an existing message filter on a
ZMQ_SUB socket. The filter specified must match an existing filter
previously established with the
ZMQ_SUBSCRIBE option. If the socket has
several instances of the same filter attached the
ZMQ_UNSUBSCRIBE
option shall remove only one instance, leaving the rest in place and
functional.
Option value type |
binary data |
Option value unit |
N/A |
Default value |
N/A |
Applicable socket types |
ZMQ_SUB |
ZMQ_RCVTIMEO: Maximum time before a recv operation returns with EAGAIN¶
Sets the timeout for receive operation on the socket. If the value is 0,
zmq_recv(3) will return immediately, with a EAGAIN error if there is no
message to receive. If the value is -1, it will block until a message is
available. For all other values, it will wait for a message for that amount of
time before returning with an EAGAIN error.
Option value type |
int |
Option value unit |
milliseconds |
Default value |
-1 (infinite) |
Applicable socket types |
all |
ZMQ_SNDTIMEO: Maximum time before a send operation returns with EAGAIN¶
Sets the timeout for send operation on the socket. If the value is 0,
zmq_send(3) will return immediately, with a EAGAIN error if the message
cannot be sent. If the value is -1, it will block until the message is sent.
For all other values, it will try to send the message for that amount of time
before returning with an EAGAIN error.
Option value type |
int |
Option value unit |
milliseconds |
Default value |
-1 (infinite) |
Applicable socket types |
all |
ZMQ_RATE: Set multicast data rate¶
The
ZMQ_RATE option shall set the maximum send or receive data rate for
multicast transports such as
zmq_pgm(7) using the specified
socket.
Option value type |
int64_t |
Option value unit |
kilobits per second |
Default value |
100 |
Applicable socket types |
all, when using multicast transports |
ZMQ_RECOVERY_IVL: Set multicast recovery interval¶
The
ZMQ_RECOVERY_IVL option shall set the recovery interval for multicast
transports using the specified
socket. The recovery interval determines
the maximum time in seconds that a receiver can be absent from a multicast
group before unrecoverable data loss will occur.
Caution
Exercise care when setting large recovery intervals as the data needed for
recovery will be held in memory. For example, a 1 minute recovery interval at
a data rate of 1Gbps requires a 7GB in-memory buffer.
Option value type |
int64_t |
Option value unit |
seconds |
Default value |
10 |
Applicable socket types |
all, when using multicast transports |
ZMQ_RECOVERY_IVL_MSEC: Set multicast recovery interval in milliseconds¶
The
ZMQ_RECOVERY_IVL_MSEC option shall set the recovery interval,
specified in milliseconds (ms) for multicast transports using the specified
socket. The recovery interval determines the maximum time in
milliseconds that a receiver can be absent from a multicast group before
unrecoverable data loss will occur.
A non-zero value of the
ZMQ_RECOVERY_IVL_MSEC option will take precedence
over the
ZMQ_RECOVERY_IVL option, but since the default for the
ZMQ_RECOVERY_IVL_MSEC is -1, the default is to use the
ZMQ_RECOVERY_IVL option value.
Caution
Exercise care when setting large recovery intervals as the data needed for
recovery will be held in memory. For example, a 1 minute recovery interval at
a data rate of 1Gbps requires a 7GB in-memory buffer.
Option value type |
int64_t |
Option value unit |
milliseconds |
Default value |
-1 |
Applicable socket types |
all, when using multicast transports |
ZMQ_MCAST_LOOP: Control multicast loop-back¶
The
ZMQ_MCAST_LOOP option shall control whether data sent via multicast
transports using the specified
socket can also be received by the
sending host via loop-back. A value of zero disables the loop-back
functionality, while the default value of 1 enables the loop-back
functionality. Leaving multicast loop-back enabled when it is not required can
have a negative impact on performance. Where possible, disable
ZMQ_MCAST_LOOP in production environments.
Option value type |
int64_t |
Option value unit |
boolean |
Default value |
1 |
Applicable socket types |
all, when using multicast transports |
ZMQ_SNDBUF: Set kernel transmit buffer size¶
The
ZMQ_SNDBUF option shall set the underlying kernel transmit buffer
size for the
socket to the specified size in bytes. A value of zero
means leave the OS default unchanged. For details please refer to your
operating system documentation for the
SO_SNDBUF socket option.
Option value type |
uint64_t |
Option value unit |
bytes |
Default value |
0 |
Applicable socket types |
all |
ZMQ_RCVBUF: Set kernel receive buffer size¶
The
ZMQ_RCVBUF option shall set the underlying kernel receive buffer size
for the
socket to the specified size in bytes. A value of zero means
leave the OS default unchanged. For details refer to your operating system
documentation for the
SO_RCVBUF socket option.
Option value type |
uint64_t |
Option value unit |
bytes |
Default value |
0 |
Applicable socket types |
all |
ZMQ_LINGER: Set linger period for socket shutdown¶
The
ZMQ_LINGER option shall set the linger period for the specified
socket. The linger period determines how long pending messages which
have yet to be sent to a peer shall linger in memory after a socket is closed
with
zmq_close(3), and further affects the termination of the
socket’s context with
zmq_term(3). The following outlines the
different behaviours:
•The default value of -1 specifies an
infinite linger period. Pending messages shall not be discarded after a call
to zmq_close(); attempting to terminate the socket’s context
with zmq_term() shall block until all pending messages have been sent
to a peer.
•The value of 0 specifies no linger period.
Pending messages shall be discarded immediately when the socket is closed with
zmq_close().
•Positive values specify an upper bound for the
linger period in milliseconds. Pending messages shall not be discarded after a
call to
zmq_close(); attempting to terminate the socket’s
context with
zmq_term() shall block until either all pending messages
have been sent to a peer, or the linger period expires, after which any
pending messages shall be discarded.
Option value type |
int |
Option value unit |
milliseconds |
Default value |
-1 (infinite) |
Applicable socket types |
all |
ZMQ_RECONNECT_IVL: Set reconnection interval¶
The
ZMQ_RECONNECT_IVL option shall set the initial reconnection interval
for the specified
socket. The reconnection interval is the period 0MQ
shall wait between attempts to reconnect disconnected peers when using
connection-oriented transports.
Note
The reconnection interval may be randomized by 0MQ to prevent reconnection
storms in topologies with a large number of peers per socket.
Option value type |
int |
Option value unit |
milliseconds |
Default value |
100 |
Applicable socket types |
all, only for connection-oriented transports |
ZMQ_RECONNECT_IVL_MAX: Set maximum reconnection interval¶
The
ZMQ_RECONNECT_IVL_MAX option shall set the maximum reconnection
interval for the specified
socket. This is the maximum period 0MQ shall
wait between attempts to reconnect. On each reconnect attempt, the previous
interval shall be doubled untill ZMQ_RECONNECT_IVL_MAX is reached. This allows
for exponential backoff strategy. Default value means no exponential backoff
is performed and reconnect interval calculations are only based on
ZMQ_RECONNECT_IVL.
Note
Values less than ZMQ_RECONNECT_IVL will be ignored.
Option value type |
int |
Option value unit |
milliseconds |
Default value |
0 (only use ZMQ_RECONNECT_IVL) |
Applicable socket types |
all, only for connection-oriented transports |
ZMQ_BACKLOG: Set maximum length of the queue of outstanding connections¶
The
ZMQ_BACKLOG option shall set the maximum length of the queue of
outstanding peer connections for the specified
socket; this only
applies to connection-oriented transports. For details refer to your operating
system documentation for the
listen function.
Option value type |
int |
Option value unit |
connections |
Default value |
100 |
Applicable socket types |
all, only for connection-oriented transports. |
RETURN VALUE¶
The
zmq_setsockopt() function shall return zero if successful. Otherwise
it shall return -1 and set
errno to one of the values defined below.
ERRORS¶
EINVAL
The requested option option_name is unknown, or
the requested option_len or option_value is invalid.
ETERM
The 0MQ context associated with the specified
socket was terminated.
ENOTSOCK
The provided socket was invalid.
EINTR
The operation was interrupted by delivery of a
signal.
EXAMPLE¶
Subscribing to messages on a ZMQ_SUB socket.
/* Subscribe to all messages */
rc = zmq_setsockopt (socket, ZMQ_SUBSCRIBE, "", 0);
assert (rc == 0);
/* Subscribe to messages prefixed with "ANIMALS.CATS" */
rc = zmq_setsockopt (socket, ZMQ_SUBSCRIBE, "ANIMALS.CATS", 12);
Setting I/O thread affinity.
int64_t affinity;
/* Incoming connections on TCP port 5555 shall be handled by I/O thread 1 */
affinity = 1;
rc = zmq_setsockopt (socket, ZMQ_AFFINITY, &affinity, sizeof affinity);
assert (rc);
rc = zmq_bind (socket, "tcp://lo:5555");
assert (rc);
/* Incoming connections on TCP port 5556 shall be handled by I/O thread 2 */
affinity = 2;
rc = zmq_setsockopt (socket, ZMQ_AFFINITY, &affinity, sizeof affinity);
assert (rc);
rc = zmq_bind (socket, "tcp://lo:5556");
assert (rc);
SEE ALSO¶
zmq_getsockopt(3) zmq_socket(3) zmq(7)
AUTHORS¶
This manual page was written by the 0MQ community.