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NAME

       xs_setsockopt - set Crossroads socket options

SYNOPSIS

       int xs_setsockopt (void *socket, int option_name, const void
       *option_value, size_t option_len);

       Caution: All options, with the exception of XS_SUBSCRIBE,
       XS_UNSUBSCRIBE and XS_LINGER, only take effect for subsequent socket
       bind/connects.

DESCRIPTION

       The xs_setsockopt() function shall set the option specified by the
       option_name argument to the value pointed to by the option_value
       argument for the Crossroads 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 xs_setsockopt()
       function:

   XS_SNDHWM: Set high water mark for outbound messages
       The XS_SNDHWM option shall set the high water mark for outbound
       messages on the specified socket. The high water mark is a hard limit
       on the maximum number of outstanding messages the library 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, the library shall take
       appropriate action such as blocking or dropping sent messages. Refer to
       the individual socket descriptions in xs_socket(3) for details on the
       exact action taken for each socket type.

       Option value type         int

       Option value unit         messages

       Default value             1000

       Applicable socket types   all

   XS_RCVHWM: Set high water mark for inbound messages
       The XS_RCVHWM option shall set the high water mark for inbound messages
       on the specified socket. The high water mark is a hard limit on the
       maximum number of outstanding messages the libray 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, the library shall take
       appropriate action such as blocking or dropping sent messages. Refer to
       the individual socket descriptions in xs_socket(3) for details on the
       exact action taken for each socket type.

       Option value type         int

       Option value unit         messages

       Default value             1000

       Applicable socket types   all

   XS_AFFINITY: Set I/O thread affinity
       The XS_AFFINITY option shall set the I/O thread affinity for newly
       created connections on the specified socket.

       Affinity determines which threads from the Crossroads 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 Crossroads 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 xs_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

   XS_SUBSCRIBE: Establish message filter
       The XS_SUBSCRIBE option shall establish a new message filter on a
       XS_SUB socket. Newly created XS_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 XS_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   XS_SUB

   XS_UNSUBSCRIBE: Remove message filter
       The XS_UNSUBSCRIBE option shall remove an existing message filter on a
       XS_SUB socket. The filter specified must match an existing filter
       previously established with the XS_SUBSCRIBE option. If the socket has
       several instances of the same filter attached the XS_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   XS_SUB

   XS_IDENTITY: Set socket identity
       The XS_IDENTITY option shall set the identity of the specified socket.
       Socket identity is used only by request/reply pattern. Namely, it can
       be used in tandem with a XS_XREP socket to route messages to the peer
       with specific identity.

       Identity should be at least one byte and at most 255 bytes long.
       Identities starting with binary zero are reserved for use by Crossroads
       infrastructure.

       Option value type         binary data

       Option value unit         N/A

       Default value             NULL

       Applicable socket types   all

   XS_RATE: Set multicast data rate
       The XS_RATE option shall set the maximum send or receive data rate for
       multicast transports such as xs_pgm(7) using the specified socket.

       Option value type         int

       Option value unit         kilobits per second

       Default value             100

       Applicable socket types   all, when using multicast
                                 transports

   XS_RECOVERY_IVL: Set multicast recovery interval
       The XS_RECOVERY_IVL option shall set the recovery interval 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.

           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         int

       Option value unit         milliseconds

       Default value             10000

       Applicable socket types   all, when using multicast
                                 transports

   XS_SNDBUF: Set kernel transmit buffer size
       The XS_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         int

       Option value unit         bytes

       Default value             0

       Applicable socket types   all

   XS_RCVBUF: Set kernel receive buffer size
       The XS_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         int

       Option value unit         bytes

       Default value             0

       Applicable socket types   all

   XS_LINGER: Set linger period for socket shutdown
       The XS_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 xs_close(3), and further affects the termination of the
       socket’s context with xs_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 xs_close();
           attempting to terminate the socket’s context with xs_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 xs_close().

       ·   Positive values specify an upper bound for the linger period in
           milliseconds. Pending messages shall not be discarded after a call
           to xs_close(); attempting to terminate the socket’s context with
           xs_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

   XS_RECONNECT_IVL: Set reconnection interval
       The XS_RECONNECT_IVL option shall set the initial reconnection interval
       for the specified socket. The reconnection interval is the period the
       library shall wait between attempts to reconnect disconnected peers
       when using connection-oriented transports.

           Note
           The reconnection interval may be randomized by the library 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

   XS_RECONNECT_IVL_MAX: Set maximum reconnection interval
       The XS_RECONNECT_IVL_MAX option shall set the maximum reconnection
       interval for the specified socket. This is the maximum period the
       library shall wait between attempts to reconnect. On each reconnect
       attempt, the previous interval shall be doubled untill
       XS_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 XS_RECONNECT_IVL.

           Note
           Values less than XS_RECONNECT_IVL will be ignored.

       Option value type         int

       Option value unit         milliseconds

       Default value             0 (only use
                                 XS_RECONNECT_IVL)

       Applicable socket types   all, only for
                                 connection-oriented
                                 transports

   XS_BACKLOG: Set maximum length of the queue of outstanding connections
       The XS_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.

   XS_MAXMSGSIZE: Maximum acceptable inbound message size
       Limits the size of the inbound message. If a peer sends a message
       larger than XS_MAXMSGSIZE it is disconnected.

       Option value type         uint64_t

       Option value unit         bytes

       Default value             2^64-1

       Applicable socket types   all

   XS_MULTICAST_HOPS: Maximum network hops for multicast packets
       Sets the time-to-live field in every multicast packet sent from this
       socket. The default is 1 which means that the multicast packets don’t
       leave the local network.

       Option value type         int

       Option value unit         network hops

       Default value             1

       Applicable socket types   all, when using multicast
                                 transports

   XS_RCVTIMEO: Maximum time before a recv operation returns with EAGAIN
       Sets the timeout for receive operation on the socket. If the value is
       0, xs_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

   XS_SNDTIMEO: Maximum time before a send operation returns with EAGAIN
       Sets the timeout for send operation on the socket. If the value is 0,
       xs_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

   XS_IPV4ONLY: Use IPv4-only sockets
       Sets the underlying native socket type. A value of 1 will use IPv4
       sockets, while the value of 0 will use IPv6 sockets. An IPv6 socket
       lets applications connect to and accept connections from both IPv4 and
       IPv6 hosts.

       Option value type         int

       Option value unit         boolean

       Default value             1 (true)

       Applicable socket types   all, when using TCP
                                 transport.

   XS_KEEPALIVE: Enable transport keepalives
       When set to 1, this option enables use of protocol keepalives on the
       socket, if supported by the underlying transport protocol.

       Option value type         int

       Option value unit         boolean

       Default value             0 (false)

       Applicable socket types   all, when using TCP
                                 transport.

   XS_SURVEY_TIMEOUT: Sets the deadline for the survey
       Specifies how long to wait for responses to the survey. After the
       interval expires, any firther calls to xs_recv() will return EAGAIN
       error. All the responses received later on will be silently discarded.
       Value of -1 means infinite.

       Option value type         int

       Option value unit         milliseconds

       Default value             -1 (infinite)

       Applicable socket types   XS_SURVEYOR

RETURN VALUE

       The xs_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 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 XS_SUB socket.

           /* Subscribe to all messages */
           rc = xs_setsockopt (socket, XS_SUBSCRIBE, "", 0);
           assert (rc == 0);
           /* Subscribe to messages prefixed with "ANIMALS.CATS" */
           rc = xs_setsockopt (socket, XS_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 = xs_setsockopt (socket, XS_AFFINITY, &affinity, sizeof affinity);
           assert (rc == 0);
           rc = xs_bind (socket, "tcp://lo:5555");
           assert (rc != -1);
           /* Incoming connections on TCP port 5556 shall be handled by I/O thread 2 */
           affinity = 2;
           rc = xs_setsockopt (socket, XS_AFFINITY, &affinity, sizeof affinity);
           assert (rc == 0);
           rc = xs_bind (socket, "tcp://lo:5556");
           assert (rc != -1);

SEE ALSO

       xs_getsockopt(3) xs_socket(3) xs(7)

AUTHORS

       The Crossroads documentation was written by Martin Sustrik
       <sustrik@250bpm.com[1]> and Martin Lucina <martin@lucina.net[2]>.

NOTES

        1. sustrik@250bpm.com
           mailto:sustrik@250bpm.com

        2. martin@lucina.net
           mailto:martin@lucina.net



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