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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"

"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<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 &lt;systemd/sd-daemon.h&gt;</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,

&gt; 0 is returned, otherwise 0 is returned. Only if

the return value is &gt; 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 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>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>