mirror of
https://github.com/systemd/systemd.git
synced 2024-11-27 20:23:36 +08:00
172 lines
6.7 KiB
XML
172 lines
6.7 KiB
XML
<?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>
|