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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">
<!--
SPDX-License-Identifier: LGPL-2.1+
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.
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>
<para>Use
<citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
to enable automatic watchdog support in
<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>-based event loops.</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 function 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>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>,
<citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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