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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
e735f4d4 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
6 | This file is part of systemd. | |
7 | ||
8 | Copyright 2013 Lennart Poettering | |
9 | ||
10 | systemd is free software; you can redistribute it and/or modify it | |
11 | under the terms of the GNU Lesser General Public License as published by | |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
13 | (at your option) any later version. | |
14 | ||
15 | systemd is distributed in the hope that it will be useful, but | |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
18 | Lesser General Public License for more details. | |
19 | ||
20 | You should have received a copy of the GNU Lesser General Public License | |
21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
22 | --> | |
23 | ||
24 | <refentry id="sd_watchdog_enabled" | |
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25 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
26 | ||
27 | <refentryinfo> | |
28 | <title>sd_watchdog_enabled</title> | |
29 | <productname>systemd</productname> | |
30 | ||
31 | <authorgroup> | |
32 | <author> | |
33 | <contrib>Developer</contrib> | |
34 | <firstname>Lennart</firstname> | |
35 | <surname>Poettering</surname> | |
36 | <email>lennart@poettering.net</email> | |
37 | </author> | |
38 | </authorgroup> | |
39 | </refentryinfo> | |
40 | ||
41 | <refmeta> | |
42 | <refentrytitle>sd_watchdog_enabled</refentrytitle> | |
43 | <manvolnum>3</manvolnum> | |
44 | </refmeta> | |
45 | ||
46 | <refnamediv> | |
47 | <refname>sd_watchdog_enabled</refname> | |
48 | <refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose> | |
49 | </refnamediv> | |
50 | ||
51 | <refsynopsisdiv> | |
52 | <funcsynopsis> | |
53 | <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> | |
54 | ||
55 | <funcprototype> | |
56 | <funcdef>int <function>sd_watchdog_enabled</function></funcdef> | |
57 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
58 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> | |
59 | </funcprototype> | |
60 | </funcsynopsis> | |
61 | </refsynopsisdiv> | |
62 | ||
63 | <refsect1> | |
64 | <title>Description</title> | |
65 | <para><function>sd_watchdog_enabled()</function> may be called by | |
66 | a service to detect whether the service manager expects regular | |
67 | keep-alive watchdog notification events from it, and the timeout | |
68 | after which the manager will act on the service if it did not get | |
69 | such a notification.</para> | |
70 | ||
71 | <para>If the <varname>$WATCHDOG_USEC</varname> environment | |
72 | variable is set, and the <varname>$WATCHDOG_PID</varname> variable | |
73 | is unset or set to the PID of the current process, the service | |
74 | manager expects notifications from this process. The manager will | |
75 | usually terminate a service when it does not get a notification | |
76 | message within the specified time after startup and after each | |
77 | previous message. It is recommended that a daemon sends a | |
78 | keep-alive notification message to the service manager every half | |
79 | of the time returned here. Notification messages may be sent with | |
80 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
81 | with a message string of <literal>WATCHDOG=1</literal>.</para> | |
82 | ||
83 | <para>If the <parameter>unset_environment</parameter> parameter is | |
84 | non-zero, <function>sd_watchdog_enabled()</function> will unset | |
85 | the <varname>$WATCHDOG_USEC</varname> and | |
86 | <varname>$WATCHDOG_PID</varname> environment variables before | |
87 | returning (regardless of whether the function call itself | |
88 | succeeded or not). Those variables are no longer inherited by | |
89 | child processes. Further calls to | |
90 | <function>sd_watchdog_enabled()</function> will also return with | |
91 | zero.</para> | |
92 | ||
93 | <para>If the <parameter>usec</parameter> parameter is non-NULL, | |
94 | <function>sd_watchdog_enabled()</function> will write the timeout | |
95 | in µs for the watchdog logic to it.</para> | |
96 | ||
97 | <para>To enable service supervision with the watchdog logic, use | |
98 | <varname>WatchdogSec=</varname> in service files. See | |
99 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
100 | for details.</para> | |
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101 | |
102 | <para>Use | |
103 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
104 | to enable automatic watchdog support in | |
105 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>-based event loops.</para> | |
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106 | </refsect1> |
107 | ||
108 | <refsect1> | |
109 | <title>Return Value</title> | |
110 | ||
111 | <para>On failure, this call returns a negative errno-style error | |
112 | code. If the service manager expects watchdog keep-alive | |
113 | notification messages to be sent, > 0 is returned, otherwise 0 | |
114 | is returned. Only if the return value is > 0, the | |
115 | <parameter>usec</parameter> parameter is valid after the | |
116 | call.</para> | |
117 | </refsect1> | |
118 | ||
119 | <refsect1> | |
120 | <title>Notes</title> | |
121 | ||
122 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> | |
123 | ||
124 | <para>Internally, this functions parses the | |
125 | <varname>$WATCHDOG_PID</varname> and | |
126 | <varname>$WATCHDOG_USEC</varname> environment variable. The call | |
127 | will ignore these variables if <varname>$WATCHDOG_PID</varname> | |
128 | does not contain the PID of the current process, under the | |
129 | assumption that in that case, the variables were set for a | |
130 | different process further up the process tree.</para> | |
131 | </refsect1> | |
132 | ||
133 | <refsect1> | |
134 | <title>Environment</title> | |
135 | ||
136 | <variablelist class='environment-variables'> | |
137 | <varlistentry> | |
138 | <term><varname>$WATCHDOG_PID</varname></term> | |
139 | ||
140 | <listitem><para>Set by the system manager for supervised | |
141 | process for which watchdog support is enabled, and contains | |
142 | the PID of that process. See above for | |
143 | details.</para></listitem> | |
144 | </varlistentry> | |
145 | ||
146 | <varlistentry> | |
147 | <term><varname>$WATCHDOG_USEC</varname></term> | |
148 | ||
149 | <listitem><para>Set by the system manager for supervised | |
150 | process for which watchdog support is enabled, and contains | |
151 | the watchdog timeout in µs See above for | |
152 | details.</para></listitem> | |
153 | </varlistentry> | |
154 | </variablelist> | |
155 | </refsect1> | |
156 | ||
157 | <refsect1> | |
158 | <title>History</title> | |
159 | ||
160 | <para>The watchdog functionality and the | |
161 | <varname>$WATCHDOG_USEC</varname> variable were added in | |
162 | systemd-41.</para> | |
163 | ||
164 | <para><function>sd_watchdog_enabled()</function> function was | |
db2df898 | 165 | added in systemd-209. Since that version, the |
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166 | <varname>$WATCHDOG_PID</varname> variable is also set.</para> |
167 | </refsect1> | |
168 | ||
169 | <refsect1> | |
170 | <title>See Also</title> | |
171 | <para> | |
172 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
173 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
174 | <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
175 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
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176 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
177 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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178 | </para> |
179 | </refsect1> | |
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180 | |
181 | </refentry> |