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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
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6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
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8 | This file is part of systemd. |
9 | ||
10 | Copyright 2013 Lennart Poettering | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
21 | ||
22 | You should have received a copy of the GNU Lesser General Public License | |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
24 | --> | |
25 | ||
6a70f3aa | 26 | <refentry id="sd_watchdog_enabled" |
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27 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
28 | ||
29 | <refentryinfo> | |
30 | <title>sd_watchdog_enabled</title> | |
31 | <productname>systemd</productname> | |
32 | ||
33 | <authorgroup> | |
34 | <author> | |
35 | <contrib>Developer</contrib> | |
36 | <firstname>Lennart</firstname> | |
37 | <surname>Poettering</surname> | |
38 | <email>lennart@poettering.net</email> | |
39 | </author> | |
40 | </authorgroup> | |
41 | </refentryinfo> | |
42 | ||
43 | <refmeta> | |
44 | <refentrytitle>sd_watchdog_enabled</refentrytitle> | |
45 | <manvolnum>3</manvolnum> | |
46 | </refmeta> | |
47 | ||
48 | <refnamediv> | |
49 | <refname>sd_watchdog_enabled</refname> | |
50 | <refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose> | |
51 | </refnamediv> | |
52 | ||
53 | <refsynopsisdiv> | |
54 | <funcsynopsis> | |
55 | <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> | |
56 | ||
57 | <funcprototype> | |
58 | <funcdef>int <function>sd_watchdog_enabled</function></funcdef> | |
59 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
60 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> | |
61 | </funcprototype> | |
62 | </funcsynopsis> | |
63 | </refsynopsisdiv> | |
64 | ||
65 | <refsect1> | |
66 | <title>Description</title> | |
67 | <para><function>sd_watchdog_enabled()</function> may be called by | |
68 | a service to detect whether the service manager expects regular | |
69 | keep-alive watchdog notification events from it, and the timeout | |
70 | after which the manager will act on the service if it did not get | |
71 | such a notification.</para> | |
72 | ||
73 | <para>If the <varname>$WATCHDOG_USEC</varname> environment | |
74 | variable is set, and the <varname>$WATCHDOG_PID</varname> variable | |
75 | is unset or set to the PID of the current process, the service | |
76 | manager expects notifications from this process. The manager will | |
77 | usually terminate a service when it does not get a notification | |
78 | message within the specified time after startup and after each | |
79 | previous message. It is recommended that a daemon sends a | |
80 | keep-alive notification message to the service manager every half | |
81 | of the time returned here. Notification messages may be sent with | |
82 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
83 | with a message string of <literal>WATCHDOG=1</literal>.</para> | |
84 | ||
85 | <para>If the <parameter>unset_environment</parameter> parameter is | |
86 | non-zero, <function>sd_watchdog_enabled()</function> will unset | |
87 | the <varname>$WATCHDOG_USEC</varname> and | |
88 | <varname>$WATCHDOG_PID</varname> environment variables before | |
89 | returning (regardless of whether the function call itself | |
90 | succeeded or not). Those variables are no longer inherited by | |
91 | child processes. Further calls to | |
92 | <function>sd_watchdog_enabled()</function> will also return with | |
93 | zero.</para> | |
94 | ||
95 | <para>If the <parameter>usec</parameter> parameter is non-NULL, | |
96 | <function>sd_watchdog_enabled()</function> will write the timeout | |
97 | in µs for the watchdog logic to it.</para> | |
98 | ||
99 | <para>To enable service supervision with the watchdog logic, use | |
100 | <varname>WatchdogSec=</varname> in service files. See | |
101 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
102 | for details.</para> | |
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103 | |
104 | <para>Use | |
105 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
106 | to enable automatic watchdog support in | |
107 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>-based event loops.</para> | |
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108 | </refsect1> |
109 | ||
110 | <refsect1> | |
111 | <title>Return Value</title> | |
112 | ||
113 | <para>On failure, this call returns a negative errno-style error | |
114 | code. If the service manager expects watchdog keep-alive | |
115 | notification messages to be sent, > 0 is returned, otherwise 0 | |
116 | is returned. Only if the return value is > 0, the | |
117 | <parameter>usec</parameter> parameter is valid after the | |
118 | call.</para> | |
119 | </refsect1> | |
120 | ||
121 | <refsect1> | |
122 | <title>Notes</title> | |
123 | ||
124 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> | |
125 | ||
fa000db3 | 126 | <para>Internally, this function parses the |
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127 | <varname>$WATCHDOG_PID</varname> and |
128 | <varname>$WATCHDOG_USEC</varname> environment variable. The call | |
129 | will ignore these variables if <varname>$WATCHDOG_PID</varname> | |
130 | does not contain the PID of the current process, under the | |
131 | assumption that in that case, the variables were set for a | |
132 | different process further up the process tree.</para> | |
133 | </refsect1> | |
134 | ||
135 | <refsect1> | |
136 | <title>Environment</title> | |
137 | ||
138 | <variablelist class='environment-variables'> | |
139 | <varlistentry> | |
140 | <term><varname>$WATCHDOG_PID</varname></term> | |
141 | ||
142 | <listitem><para>Set by the system manager for supervised | |
143 | process for which watchdog support is enabled, and contains | |
144 | the PID of that process. See above for | |
145 | details.</para></listitem> | |
146 | </varlistentry> | |
147 | ||
148 | <varlistentry> | |
149 | <term><varname>$WATCHDOG_USEC</varname></term> | |
150 | ||
151 | <listitem><para>Set by the system manager for supervised | |
152 | process for which watchdog support is enabled, and contains | |
fa000db3 | 153 | the watchdog timeout in µs. See above for |
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154 | details.</para></listitem> |
155 | </varlistentry> | |
156 | </variablelist> | |
157 | </refsect1> | |
158 | ||
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159 | <refsect1> |
160 | <title>See Also</title> | |
161 | <para> | |
162 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
163 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
164 | <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
165 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
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166 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
167 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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168 | </para> |
169 | </refsect1> | |
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170 | |
171 | </refentry> |