x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_EVENT_SOURCE_SET_RATELsd_event_source_set_rSD_EVENT_SOURCE_SET_RATELIMIT(3)
NAME
sd_event_source_set_ratelimit, sd_event_source_get_ratelimit,
sd_event_source_is_ratelimited,
sd_event_source_set_ratelimit_expire_callback,
sd_event_source_leave_ratelimit - Configure rate limiting on event
sources
SYNOPSIS
#include <systemd/sd-event.h>
int sd_event_source_set_ratelimit(sd_event_source *source,
uint64_t interval_usec,
unsigned burst);
int sd_event_source_get_ratelimit(sd_event_source *source,
uint64_t* ret_interval_usec,
unsigned* ret_burst);
int sd_event_source_is_ratelimited(sd_event_source *source);
int
sd_event_source_set_ratelimit_expire_callback(sd_event_source *source,
sd_event_handler_tcallback);
int sd_event_source_leave_ratelimit(sd_event_source *source);
DESCRIPTION
sd_event_source_set_ratelimit() may be used to enforce rate limiting on
an event source. When used an event source will be temporarily turned
off when it fires more often then a specified burst number within a
specified time interval. This is useful as simple mechanism to avoid
event source starvation if high priority event sources fire very
frequently.
Pass the event source to operate on as first argument, a time interval
in microseconds as second argument and a maximum dispatch limit
("burst") as third parameter. Whenever the event source is dispatched
more often than the specified burst within the specified interval it is
placed in a mode similar to being disabled with
sd_event_source_set_enabled(3) and the SD_EVENT_OFF parameter. However
it is disabled only temporarily - once the specified interval is over
regular operation resumes. It is again disabled temporarily once the
specified rate limiting is hit the next time. If either the interval or
the burst value are specified as zero, rate limiting is turned off. By
default event sources do not have rate limiting enabled. Note that rate
limiting and disabling via sd_event_source_set_enabled() are
independent of each other, and an event source will only effect event
loop wake-ups and is dispatched while it both is enabled and rate
limiting is not in effect.
sd_event_source_get_ratelimit() may be used to query the current rate
limiting parameters set on the event source object source. The
previously set interval and burst vales are returned in the second and
third argument.
sd_event_source_is_ratelimited() may be used to query whether the event
source is currently affected by rate limiting, i.e. it has recently hit
the rate limit and is currently temporarily disabled due to that.
sd_event_source_set_ratelimit_expire_callback() may be used to set a
callback function that is invoked every time the event source leaves
rate limited state. Note that function is called in the same event loop
iteration in which state transition occurred.
sd_event_source_leave_ratelimit() may be used to immediately reenable
an event source that was temporarily disabled due to rate limiting.
This will reset the ratelimit counters for the current time interval.
Rate limiting is currently implemented for I/O, timer, signal, defer
and inotify event sources.
RETURN VALUE
On success, sd_event_source_set_ratelimit(),
sd_event_source_set_ratelimit_expire_callback and
sd_event_source_get_ratelimit() return a non-negative integer. On
failure, they return a negative errno-style error code.
sd_event_source_is_ratelimited() returns zero if rate limiting is
currently not in effect and greater than zero if it is in effect; it
returns a negative errno-style error code on failure.
sd_event_source_leave_ratelimit() returns zero if rate limiting wasn't
in effect on the specified event source, and positive if it was and
rate limiting is now turned off again; it returns a negative
errno-style error code on failure.
Errors
Returned errors may indicate the following problems:
-EINVAL
source is not a valid pointer to an sd_event_source object.
-ECHILD
The event loop has been created in a different process, library or
module instance.
-EDOM
It was attempted to use the rate limiting feature on an event
source type that does not support rate limiting.
-ENOEXEC
sd_event_source_get_ratelimit() was called on an event source that
doesn't have rate limiting configured.
NOTES
Functions described here are available as a shared library, which can
be compiled against and linked to with the libsystemd pkg-config(1)
file.
The code described here uses getenv(3), which is declared to be not
multi-thread-safe. This means that the code calling the functions
described here must not call setenv(3) from a parallel thread. It is
recommended to only do calls to setenv() from an early phase of the
program when no other threads have been started.
SEE ALSO
sd-event(3), sd_event_add_io(3), sd_event_add_time(3),
sd_event_add_signal(3), sd_event_add_inotify(3), sd_event_add_defer(3),
sd_event_source_set_enabled(3)
systemd 254 SD_EVENT_SOURCE_SET_RATELIMIT(3)
Want to link to this manual page? Use this URL:
<http://star2.abcm.com/cgi-bin/bsdi-man?query=sd_event_source_set_ratelimit&sektion=3&manpath=>