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diff --git a/man/sd_event_source_set_ratelimit.xml b/man/sd_event_source_set_ratelimit.xml new file mode 100644 index 0000000..b8e6380 --- /dev/null +++ b/man/sd_event_source_set_ratelimit.xml @@ -0,0 +1,160 @@ +<?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> |