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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
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 | ||
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24 | <refentry id="sd_watchdog_enabled" |
25 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
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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>const 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 | |
66 | be called by a service to detect whether the service | |
67 | manager expects regular keep-alive watchdog | |
68 | notification events from it, and the timeout after | |
69 | which the manager will act on the service if it did | |
70 | not get such a notification.</para> | |
71 | ||
72 | <para>If the <parameter>unset_environment</parameter> | |
73 | parameter is non-zero, | |
74 | <function>sd_watchdog_enabled()</function> will unset | |
75 | the <varname>$WATCHDOG_USEC</varname> and | |
76 | <varname>$WATCHDOG_PID</varname> environment variables | |
494a6682 | 77 | before returning (regardless of whether the function call |
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78 | itself succeeded or not). Further calls to |
79 | <function>sd_watchdog_enabled()</function> will then | |
80 | return with zero, but the variable is no longer | |
81 | inherited by child processes.</para> | |
82 | ||
83 | <para>If the <parameter>usec</parameter> parameter is | |
b040723e | 84 | non-NULL, <function>sd_watchdog_enabled()</function> |
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85 | will return the timeout in µs for the watchdog |
86 | logic. The service manager will usually terminate a | |
87 | service when it did not get a notification message | |
88 | within the specified time after startup and after each | |
89 | previous message. It is recommended that a daemon | |
90 | sends a keep-alive notification message to the service | |
91 | manager every half of the time returned | |
92 | here. Notification messages may be sent with | |
93 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
94 | with a message string of | |
95 | <literal>WATCHDOG=1</literal>.</para> | |
96 | ||
97 | <para>To enable service supervision with the watchdog | |
b040723e | 98 | logic, use <varname>WatchdogSec=</varname> in service |
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99 | files. See |
100 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
101 | for details.</para> | |
102 | </refsect1> | |
103 | ||
104 | <refsect1> | |
105 | <title>Return Value</title> | |
106 | ||
107 | <para>On failure, this call returns a negative | |
108 | errno-style error code. If the service manager expects | |
109 | watchdog keep-alive notification messages to be sent, | |
110 | > 0 is returned, otherwise 0 is returned. Only if | |
b040723e | 111 | the return value is > 0, the |
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112 | <parameter>usec</parameter> parameter is valid after |
113 | the call.</para> | |
114 | </refsect1> | |
115 | ||
116 | <refsect1> | |
117 | <title>Notes</title> | |
118 | ||
6a70f3aa | 119 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> |
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120 | |
121 | <para>Internally, this functions parses the | |
122 | <varname>$WATCHDOG_PID</varname> and | |
123 | <varname>$WATCHDOG_USEC</varname> environment | |
124 | variable. The call will ignore these variables if | |
125 | <varname>$WATCHDOG_PID</varname> does containe the PID | |
126 | of the current process, under the assumption that in | |
b040723e | 127 | that case, the variables were set for a different |
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128 | process further up the process tree.</para> |
129 | ||
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130 | </refsect1> |
131 | ||
132 | <refsect1> | |
133 | <title>Environment</title> | |
134 | ||
135 | <variablelist class='environment-variables'> | |
136 | <varlistentry> | |
137 | <term><varname>$WATCHDOG_PID</varname></term> | |
138 | ||
139 | <listitem><para>Set by the system | |
140 | manager for supervised process for | |
141 | which watchdog support is enabled, and | |
142 | contains the PID of that process. See | |
143 | above for details.</para></listitem> | |
144 | </varlistentry> | |
145 | ||
146 | <varlistentry> | |
147 | <term><varname>$WATCHDOG_USEC</varname></term> | |
148 | ||
149 | <listitem><para>Set by the system | |
150 | manager for supervised process for | |
151 | which watchdog support is enabled, and | |
152 | contains the watchdog timeout in µs | |
153 | See above for | |
154 | details.</para></listitem> | |
155 | </varlistentry> | |
156 | </variablelist> | |
157 | </refsect1> | |
158 | ||
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>, | |
166 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
167 | </para> | |
168 | </refsect1> | |
169 | ||
170 | </refentry> |