mirror of
https://github.com/systemd/systemd-stable.git
synced 2024-12-23 17:34:00 +03:00
161 lines
7.3 KiB
XML
161 lines
7.3 KiB
XML
<?xml version='1.0'?>
|
||
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
||
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
||
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
|
||
|
||
<refentry id="sd_event_source_set_ratelimit" xmlns:xi="http://www.w3.org/2001/XInclude">
|
||
|
||
<refentryinfo>
|
||
<title>sd_event_source_set_ratelimit</title>
|
||
<productname>systemd</productname>
|
||
</refentryinfo>
|
||
|
||
<refmeta>
|
||
<refentrytitle>sd_event_source_set_ratelimit</refentrytitle>
|
||
<manvolnum>3</manvolnum>
|
||
</refmeta>
|
||
|
||
<refnamediv>
|
||
<refname>sd_event_source_set_ratelimit</refname>
|
||
<refname>sd_event_source_get_ratelimit</refname>
|
||
<refname>sd_event_source_is_ratelimited</refname>
|
||
<refname>sd_event_source_set_ratelimit_expire_callback</refname>
|
||
|
||
<refpurpose>Configure rate limiting on event sources</refpurpose>
|
||
</refnamediv>
|
||
|
||
<refsynopsisdiv>
|
||
<funcsynopsis>
|
||
<funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_event_source_set_ratelimit</function></funcdef>
|
||
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
||
<paramdef>uint64_t <parameter>interval_usec</parameter></paramdef>
|
||
<paramdef>unsigned <parameter>burst</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_event_source_get_ratelimit</function></funcdef>
|
||
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
||
<paramdef>uint64_t* <parameter>ret_interval_usec</parameter></paramdef>
|
||
<paramdef>unsigned* <parameter>ret_burst</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_event_source_is_ratelimited</function></funcdef>
|
||
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_event_source_set_ratelimit_expire_callback</function></funcdef>
|
||
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
||
<paramdef>sd_event_handler_t<parameter>callback</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
</funcsynopsis>
|
||
</refsynopsisdiv>
|
||
|
||
<refsect1>
|
||
<title>Description</title>
|
||
|
||
<para><function>sd_event_source_set_ratelimit()</function> 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.</para>
|
||
|
||
<para>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
|
||
<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
and the <constant>SD_EVENT_OFF</constant> 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 <function>sd_event_source_set_enabled()</function> 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.</para>
|
||
|
||
<para><function>sd_event_source_get_ratelimit()</function> may be used to query the current rate limiting
|
||
parameters set on the event source object <parameter>source</parameter>. The previously set interval and
|
||
burst vales are returned in the second and third argument.</para>
|
||
|
||
<para><function>sd_event_source_is_ratelimited()</function> 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.</para>
|
||
|
||
<para><function>sd_event_source_set_ratelimit_expire_callback</function> 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.</para>
|
||
|
||
<para>Rate limiting is currently implemented for I/O, timer, signal, defer and inotify event
|
||
sources.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Return Value</title>
|
||
|
||
<para>On success, <function>sd_event_source_set_ratelimit()</function>,
|
||
<function>sd_event_source_set_ratelimit_expire_callback</function> and
|
||
<function>sd_event_source_get_ratelimit()</function> return a non-negative integer. On failure, they return
|
||
a negative errno-style error code. <function>sd_event_source_is_ratelimited</function> 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.</para>
|
||
|
||
<refsect2>
|
||
<title>Errors</title>
|
||
|
||
<para>Returned errors may indicate the following problems:</para>
|
||
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><constant>-EINVAL</constant></term>
|
||
|
||
<listitem><para><parameter>source</parameter> is not a valid pointer to an
|
||
<structname>sd_event_source</structname> object.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><constant>-ECHILD</constant></term>
|
||
|
||
<listitem><para>The event loop has been created in a different process.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><constant>-EDOM</constant></term>
|
||
|
||
<listitem><para>It was attempted to use the rate limiting feature on an event source type that does
|
||
not support rate limiting.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><constant>-ENOEXEC</constant></term>
|
||
|
||
<listitem><para><function>sd_event_source_get_ratelimit()</function> was called on an event source
|
||
that doesn't have rate limiting configured.</para></listitem>
|
||
</varlistentry>
|
||
|
||
</variablelist>
|
||
</refsect2>
|
||
</refsect1>
|
||
|
||
<xi:include href="libsystemd-pkgconfig.xml" />
|
||
|
||
<refsect1>
|
||
<title>See Also</title>
|
||
|
||
<para>
|
||
<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
</para>
|
||
</refsect1>
|
||
|
||
</refentry>
|