1SD_EVENT_SOURCE_SET_RATELIsMdI_Te(v3e)nt_source_set_raStDe_lEiVmEiNtT_SOURCE_SET_RATELIMIT(3)
2
6 sd_event_source_set_ratelimit, sd_event_source_get_ratelimit,
7 sd_event_source_is_ratelimited - Configure rate limiting on event
8 sources
9
11 #include <systemd/sd-event.h>
12 int sd_event_source_set_ratelimit(sd_event_source *source,
14 uint64_t interval_usec,
15 unsigned burst);
16 int sd_event_source_get_ratelimit(sd_event_source *source,
18 uint64_t* ret_interval_usec,
19 unsigned* ret_burst);
20 int sd_event_source_is_ratelimited(sd_event_source *source);
22
24 sd_event_source_set_ratelimit() may be used to enforce rate limiting on
25 an event source. When used an event source will be temporarily turned
26 off when it fires more often then a specified burst number within a
27 specified time interval. This is useful as simple mechanism to avoid
28 event source starvation if high priority event sources fire very
29 frequently.
30 Pass the event source to operate on as first argument, a time interval
32 in microseconds as second argument and a maximum dispatch limit
33 ("burst") as third parameter. Whenever the event source is dispatched
34 more often than the specified burst within the specified interval it is
35 placed in a mode similar to being disabled with
36 sd_event_source_set_enabled(3) and the SD_EVENT_OFF parameter. However
37 it is disabled only temporarily – once the specified interval is over
38 regular operation resumes. It is again disabled temporarily once the
39 specified rate limiting is hit the next time. If either the interval or
40 the burst value are specified as zero, rate limiting is turned off. By
41 default event sources do not have rate limiting enabled. Note that rate
42 limiting and disabling via sd_event_source_set_enabled() are
43 independent of each other, and an event source will only effect event
44 loop wake-ups and is dispatched while it both is enabled and rate
45 limiting is not in effect.
46 sd_event_source_get_ratelimit() may be used to query the current rate
48 limiting parameters set on the event source object source. The
49 previously set interval and burst vales are returned in the second and
50 third argument.
51 sd_event_source_is_ratelimited() may be used to query whether the event
53 source is currently affected by rate limiting, i.e. it has recently hit
54 the rate limit and is currently temporarily disabled due to that.
55 Rate limiting is currently implemented for I/O, timer, signal, defer
57 and inotify event sources.
58
60 On success, sd_event_source_set_ratelimit() and
61 sd_event_source_get_ratelimit() return a non-negative integer. On
62 failure, they return a negative errno-style error code.
63 sd_event_source_is_ratelimited returns zero if rate limiting is
64 currently not in effect and greater than zero if it is in effect; it
65 returns a negative errno-style error code on failure.
66 Errors
68 Returned errors may indicate the following problems:
69 -EINVAL
71 source is not a valid pointer to an sd_event_source object.
72 -ECHILD
74 The event loop has been created in a different process.
75 -EDOM
77 It was attempted to use the rate limiting feature on an event
78 source type that does not support rate limiting.
79 -ENOEXEC
81 sd_event_source_get_ratelimit() was called on a event source that
82 doesn't have rate limiting configured.
83
85 These APIs are implemented as a shared library, which can be compiled
86 and linked to with the libsystemd pkg-config(1) file.
87
89 sd-event(3), sd_event_add_io(3), sd_event_add_time(3),
90 sd_event_add_signal(3), sd_event_add_inotify(3), sd_event_add_defer(3),
91 sd_event_source_set_enabled(3)
92systemd 248 SD_EVENT_SOURCE_SET_RATELIMIT(3)