<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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+ This file is part of elogind.
Copyright 2013 Lennart Poettering
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+ elogind is free software; you can redistribute it and/or modify it
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+ along with elogind; If not, see <http://www.gnu.org/licenses/>.
-->
-<refentry id="sd_watchdog_enabled">
-
- <refentryinfo>
- <title>sd_watchdog_enabled</title>
- <productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
- </refentryinfo>
-
- <refmeta>
- <refentrytitle>sd_watchdog_enabled</refentrytitle>
- <manvolnum>3</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>sd_watchdog_enabled</refname>
- <refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo>
-
- <funcprototype>
- <funcdef>int <function>sd_watchdog_enabled</function></funcdef>
- <paramdef>int <parameter>unset_environment</parameter></paramdef>
- <paramdef>const uint64_t *<parameter>usec</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
- <para><function>sd_watchdog_enabled()</function> may
- be called by a service to detect whether the service
- manager expects regular keep-alive watchdog
- notification events from it, and the timeout after
- which the manager will act on the service if it did
- not get such a notification.</para>
-
- <para>If the <parameter>unset_environment</parameter>
- parameter is non-zero,
- <function>sd_watchdog_enabled()</function> will unset
- the <varname>$WATCHDOG_USEC</varname> and
- <varname>$WATCHDOG_PID</varname> environment variables
- before returning (regardless of whether the function call
- itself succeeded or not). Further calls to
- <function>sd_watchdog_enabled()</function> will then
- return with zero, but the variable is no longer
- inherited by child processes.</para>
-
- <para>If the <parameter>usec</parameter> parameter is
- non-NULL, <function>sd_watchdog_enabled()</function>
- will return the timeout in µs for the watchdog
- logic. The service manager will usually terminate a
- service when it did not get a notification message
- within the specified time after startup and after each
- previous message. It is recommended that a daemon
- sends a keep-alive notification message to the service
- manager every half of the time returned
- here. Notification messages may be sent with
- <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- with a message string of
- <literal>WATCHDOG=1</literal>.</para>
-
- <para>To enable service supervision with the watchdog
- logic, use <varname>WatchdogSec=</varname> in service
- files. See
- <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- for details.</para>
- </refsect1>
-
- <refsect1>
- <title>Return Value</title>
-
- <para>On failure, this call returns a negative
- errno-style error code. If the service manager expects
- watchdog keep-alive notification messages to be sent,
- > 0 is returned, otherwise 0 is returned. Only if
- the return value is > 0, the
- <parameter>usec</parameter> parameter is valid after
- the call.</para>
- </refsect1>
-
- <refsect1>
- <title>Notes</title>
-
- <para>These APIs are implemented as a shared library,
- which can be compiled and linked to with the
- <constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- file.</para>
-
- <para>Internally, this functions parses the
- <varname>$WATCHDOG_PID</varname> and
- <varname>$WATCHDOG_USEC</varname> environment
- variable. The call will ignore these variables if
- <varname>$WATCHDOG_PID</varname> does containe the PID
- of the current process, under the assumption that in
- that case, the variables were set for a different
- process further up the process tree.</para>
-
- </refsect1>
-
- <refsect1>
- <title>Environment</title>
-
- <variablelist class='environment-variables'>
- <varlistentry>
- <term><varname>$WATCHDOG_PID</varname></term>
-
- <listitem><para>Set by the system
- manager for supervised process for
- which watchdog support is enabled, and
- contains the PID of that process. See
- above for details.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>$WATCHDOG_USEC</varname></term>
-
- <listitem><para>Set by the system
- manager for supervised process for
- which watchdog support is enabled, and
- contains the watchdog timeout in µs
- See above for
- details.</para></listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-
- <refsect1>
- <title>See Also</title>
- <para>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- </para>
- </refsect1>
+<refentry id="sd_watchdog_enabled"
+ xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_watchdog_enabled</title>
+ <productname>elogind</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_watchdog_enabled</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_watchdog_enabled</refname>
+ <refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <elogind/sd-daemon.h></funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_watchdog_enabled</function></funcdef>
+ <paramdef>int <parameter>unset_environment</parameter></paramdef>
+ <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+ <para><function>sd_watchdog_enabled()</function> may be called by
+ a service to detect whether the service manager expects regular
+ keep-alive watchdog notification events from it, and the timeout
+ after which the manager will act on the service if it did not get
+ such a notification.</para>
+
+ <para>If the <varname>$WATCHDOG_USEC</varname> environment
+ variable is set, and the <varname>$WATCHDOG_PID</varname> variable
+ is unset or set to the PID of the current process, the service
+ manager expects notifications from this process. The manager will
+ usually terminate a service when it does not get a notification
+ message within the specified time after startup and after each
+ previous message. It is recommended that a daemon sends a
+ keep-alive notification message to the service manager every half
+ of the time returned here. Notification messages may be sent with
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ with a message string of <literal>WATCHDOG=1</literal>.</para>
+
+ <para>If the <parameter>unset_environment</parameter> parameter is
+ non-zero, <function>sd_watchdog_enabled()</function> will unset
+ the <varname>$WATCHDOG_USEC</varname> and
+ <varname>$WATCHDOG_PID</varname> environment variables before
+ returning (regardless of whether the function call itself
+ succeeded or not). Those variables are no longer inherited by
+ child processes. Further calls to
+ <function>sd_watchdog_enabled()</function> will also return with
+ zero.</para>
+
+ <para>If the <parameter>usec</parameter> parameter is non-NULL,
+ <function>sd_watchdog_enabled()</function> will write the timeout
+ in µs for the watchdog logic to it.</para>
+
+ <para>To enable service supervision with the watchdog logic, use
+ <varname>WatchdogSec=</varname> in service files. See
+ <citerefentry><refentrytitle>elogind.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On failure, this call returns a negative errno-style error
+ code. If the service manager expects watchdog keep-alive
+ notification messages to be sent, > 0 is returned, otherwise 0
+ is returned. Only if the return value is > 0, the
+ <parameter>usec</parameter> parameter is valid after the
+ call.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <xi:include href="libelogind-pkgconfig.xml" xpointer="pkgconfig-text"/>
+
+ <para>Internally, this functions parses the
+ <varname>$WATCHDOG_PID</varname> and
+ <varname>$WATCHDOG_USEC</varname> environment variable. The call
+ will ignore these variables if <varname>$WATCHDOG_PID</varname>
+ does not contain the PID of the current process, under the
+ assumption that in that case, the variables were set for a
+ different process further up the process tree.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Environment</title>
+
+ <variablelist class='environment-variables'>
+ <varlistentry>
+ <term><varname>$WATCHDOG_PID</varname></term>
+
+ <listitem><para>Set by the system manager for supervised
+ process for which watchdog support is enabled, and contains
+ the PID of that process. See above for
+ details.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$WATCHDOG_USEC</varname></term>
+
+ <listitem><para>Set by the system manager for supervised
+ process for which watchdog support is enabled, and contains
+ the watchdog timeout in µs See above for
+ details.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>History</title>
+
+ <para>The watchdog functionality and the
+ <varname>$WATCHDOG_USEC</varname> variable were added in
+ elogind-41.</para>
+
+ <para><function>sd_watchdog_enabled()</function> function was
+ added in elogind-209. Since that version the
+ <varname>$WATCHDOG_PID</varname> variable is also set.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>elogind.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
</refentry>
~ianmdlvl / elogind.git / blobdiff