<?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. 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>