diff options
Diffstat (limited to 'doc/zmq_getsockopt.txt')
| -rw-r--r-- | doc/zmq_getsockopt.txt | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/doc/zmq_getsockopt.txt b/doc/zmq_getsockopt.txt new file mode 100644 index 0000000..13243ec --- /dev/null +++ b/doc/zmq_getsockopt.txt @@ -0,0 +1,209 @@ +zmq_getsockopt(3) +================= + + +NAME +---- + +zmq_getsockopt - get 0MQ socket options + + +SYNOPSIS +-------- +*int zmq_getsockopt (void '*socket', int 'option_name', void '*option_value', size_t 'option_len');* + + +DESCRIPTION +----------- +The _zmq_getsockopt()_ function shall retrieve the value for the option +specified by the 'option_name' argument for the 0MQ socket pointed to by the +'socket' argument, and store it in the buffer pointed to by the 'option_value' +argument. The 'option_len' argument is the size in bytes of the buffer pointed +to by 'option_value'. + +The following options can be retrieved with the _zmq_getsockopt()_ function: + + +ZMQ_HWM: Retrieve high water mark +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'ZMQ_HWM' option shall retrieve the high water mark for the _message queue_ +associated with the specified 'socket'. The high water mark is a hard limit on +the number of outstanding messages in the queue; if this limit has been reached +the socket shall enter an "emergency" state and depending on the socket type, +0MQ shall take appropriate action such as blocking or dropping new messages +entering the queue. + +The default 'ZMQ_HWM' value of zero means "no limit". + +Option value type:: int64_t +Option value unit:: messages +Default value:: 0 +Applicable socket types:: all + + +ZMQ_SWAP: Retrieve disk offload size +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'ZMQ_SWAP' option shall retrieve the disk offload (swap) size for the +_message queue_ associated with the specified 'socket'. A socket which has +'ZMQ_SWAP' set to a non-zero value may exceed it's 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: Retrieve I/O thread affinity +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'ZMQ_AFFINITY' option shall retrieve 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 linkzmq:zmq_init[3] for details on allocating the number of I/O +threads for a specific _context_. + +Option value type:: int64_t +Option value unit:: N/A (bitmap) +Default value:: 0 +Applicable socket types:: N/A + + +ZMQ_IDENTITY: Retrieve socket identity +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'ZMQ_IDENTITY' option shall retrieve the identity of the specified +'socket'. Socket identity determines if existing 0MQ infastructure (_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 can 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_RATE: Retrieve multicast data rate +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'ZMQ_RATE' option shall retrieve the maximum send or receive data rate for +multicast transports using the specified 'socket'. + +Option value type:: uint64_t +Option value unit:: kilobits per second +Default value:: 100 +Applicable socket types:: all, when using multicast transports + + +ZMQ_RECOVERY_IVL: Get multicast recovery interval +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'ZMQ_RECOVERY_IVL' option shall retrieve 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. + +Option value type:: uint64_t +Option value unit:: seconds +Default value:: 10 +Applicable socket types:: all, when using multicast transports + + +ZMQ_MCAST_LOOP: Control multicast loopback +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'ZMQ_MCAST_LOOP' option controls whether data sent via multicast +transports can also be received by the sending host via loopback. A value of +zero indicates that the loopback functionality is disabled, while the default +value of 1 indicates that the loopback functionality is enabled. Leaving +multicast loopback 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:: uint64_t +Option value unit:: boolean +Default value:: 1 +Applicable socket types:: all, when using multicast transports + + +ZMQ_SNDBUF: Retrieve kernel transmit buffer size +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'ZMQ_SNDBUF' option shall retrieve the underlying kernel transmit buffer +size for the specified 'socket'. A value of zero means that the OS default is +in effect. For details 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: Retrieve kernel receive buffer size +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The 'ZMQ_RCVBUF' option shall retrieve the underlying kernel receive buffer +size for the specified 'socket'. A value of zero means that the OS default is +in effect. 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 + + +RETURN VALUE +------------ +The _zmq_getsockopt()_ 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, or the size of the buffer pointed to by +_option_value_, as specified by _option_len_, is insufficient for storing the +option value. + +*ETERM*:: +The 0MQ 'context' associated with the specified 'socket' was terminated. + + +EXAMPLE +------- +.Retrieving the high water mark +---- +/* Retrieve high water mark into hwm */ +int64_t hwm; +rc = zmq_getsockopt (socket, ZMQ_HWM, &hwm, sizeof hwm); +assert (rc == 0); +---- + + +SEE ALSO +-------- +linkzmq:zmq_setsockopt[3] +linkzmq:zmq_socket[3] +linkzmq:zmq[7] + + +AUTHORS +------- +The 0MQ documentation was written by Martin Sustrik <sustrik@250bpm.com> and +Martin Lucina <mato@kotelna.sk>. |