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156 lines
5.1 KiB
Plaintext
156 lines
5.1 KiB
Plaintext
zmq_setsockopt(3)
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=================
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NAME
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----
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zmq_setsockopt - sets a specified option on a 0MQ socket
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SYNOPSIS
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--------
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'int zmq_setsockopt (void *s, int option, const void *optval, size_t optvallen);'
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DESCRIPTION
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-----------
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Sets an option on the socket. 'option' argument specifies the option from the
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list below. 'optval' is a pointer to the value to set, 'optvallen' is the size
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of the value in bytes.
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*ZMQ_HWM*::
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High watermark for the message pipes associated with the socket. The water
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mark cannot be exceeded. If the messages don't fit into the pipe emergency
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mechanisms of the particular socket type are used (block, drop etc.) If HWM
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is set to zero, there are no limits for the content of the pipe.
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+
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Type: int64_t Unit: messages Default: 0
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*ZMQ_LWM*::
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Low watermark makes sense only if high watermark is defined (i.e. is non-zero).
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When the emergency state is reached when messages overflow the pipe, the
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emergency lasts at most till the size of the pipe decreases to low watermark.
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Normal state is resumed at that point.
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+
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Type: int64_t Unit: messages Default: 0
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*ZMQ_SWAP*::
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Swap allows the pipe to exceed high watermark. However, the data are written
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to the disk rather than held in the memory. Until high watermark is
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exceeded there is no disk activity involved though. The value of the option
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defines maximal size of the swap file.
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Type: int64_t Unit: bytes Default: 0
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*ZMQ_AFFINITY*::
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Affinity defines which threads in the thread pool will be used to handle
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newly created sockets. This way you can dedicate some of the threads (CPUs)
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to a specific work. Value of 0 means no affinity. Work is distributed
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fairly among the threads in the thread pool. For non-zero values, the lowest
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bit corresponds to the thread 1, second lowest bit to the thread 2 etc.
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Thus, value of 3 means that from now on newly created sockets will handle
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I/O activity exclusively using threads no. 1 and 2.
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+
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Type: int64_t Unit: N/A (bitmap) Default: 0
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*ZMQ_IDENTITY*::
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Identity of the socket. Identity is important when restarting applications.
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If the socket has no identity, each run of the application is completely
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separated from other runs. However, with identity application reconnects to
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existing infrastructure left by the previous run. Thus it may receive
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messages that were sent in the meantime, it shares pipe limits with the
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previous run etc.
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Type: string Unit: N/A Default: NULL
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*ZMQ_SUBSCRIBE*::
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Applicable only to ZMQ_SUB socket type. It establishes new message filter.
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When ZMQ_SUB socket is created all the incoming messages are filtered out.
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This option allows you to subscribe for all messages (""), or messages
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beginning with specific prefix (e.g. "animals.mammals.dogs."). Multiple
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filters can be attached to a single 'sub' socket. In that case message passes
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if it matches at least one of the filters.
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Type: string Unit: N/A Default: N/A
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*ZMQ_UNSUBSCRIBE*::
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Applicable only to ZMQ_SUB socket type. Removes existing message filter.
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The filter specified must match the string passed to ZMQ_SUBSCRIBE options
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exactly. If there were several instances of the same filter created,
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this options removes only one of them, leaving the rest in place
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and functional.
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Type: string Unit: N/A Default: N/A
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*ZMQ_RATE*::
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This option applies only to sending side of multicast transports (pgm & udp).
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It specifies maximal outgoing data rate that an individual sender socket
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can send.
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Type: uint64_t Unit: kilobits/second Default: 100
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*ZMQ_RECOVERY_IVL*::
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This option applies only to multicast transports (pgm & udp). It specifies
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how long can the receiver socket survive when the sender is inaccessible.
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Keep in mind that large recovery intervals at high data rates result in
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very large recovery buffers, meaning that you can easily overload your box
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by setting say 1 minute recovery interval at 1Gb/s rate (requires
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7GB in-memory buffer).
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+
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Type: uint64_t Unit: seconds Default: 10
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*ZMQ_MCAST_LOOP*::
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This option applies only to multicast transports (pgm & udp). Value of 1
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means that the mutlicast packets can be received on the box they were sent
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from. Setting the value to 0 disables the loopback functionality which
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can have negative impact on the performance. If possible, disable
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the loopback in production environments.
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+
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Type: uint64_t Unit: N/A (boolean value) Default: 1
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*ZMQ_SNDBUF*::
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Sets the underlying kernel transmit buffer size to the specified size. See
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'SO_SNDBUF' POSIX socket option. Value of zero means leaving the OS default
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unchanged.
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+
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Type: uint64_t Unit: bytes Default: 0
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*ZMQ_RCVBUF*::
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Sets the underlying kernel receive buffer size to the specified size. See
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'SO_RCVBUF' POSIX socket option. Value of zero means leaving the OS default
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unchanged.
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+
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Type: uint64_t Unit: bytes Default: 0
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RETURN VALUE
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------------
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In case of success the function returns zero. Otherwise it returns -1 and
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sets 'errno' to the appropriate value.
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ERRORS
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------
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*EINVAL*::
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unknown option, a value with incorrect length or invalid value.
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EXAMPLE
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-------
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----
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int rc = zmq_setsockopt (s, ZMQ_SUBSCRIBE, "", 0);
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assert (rc == 0);
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----
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SEE ALSO
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--------
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linkzmq:zmq_socket[3]
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linkzmq:zmq[7]
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AUTHOR
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------
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Martin Sustrik <sustrik at 250bpm dot com>
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