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-<?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">
-
-<!--
- This file is part of systemd.
-
- Copyright 2013 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
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- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
-
-<refentry id="sd_watchdog_enabled"
- xmlns:xi="http://www.w3.org/2001/XInclude">
-
- <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>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>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>
-
- <xi:include href="libsystemd-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
- systemd-41.</para>
-
- <para><function>sd_watchdog_enabled()</function> function was
- added in systemd-209. Since that version the
- <varname>$WATCHDOG_PID</varname> variable is also set.</para>
- </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>
~ianmdlvl / elogind.git / blobdiff