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);
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