+<?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 elogind.
+
+ Copyright 2013 Lennart Poettering
+
+ elogind 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.
+
+ elogind 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 elogind; 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>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