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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 | |
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11 | --> |
12 | ||
6a70f3aa | 13 | <refentry id="sd_watchdog_enabled" |
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14 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
15 | ||
16 | <refentryinfo> | |
17 | <title>sd_watchdog_enabled</title> | |
18 | <productname>systemd</productname> | |
19 | ||
20 | <authorgroup> | |
21 | <author> | |
22 | <contrib>Developer</contrib> | |
23 | <firstname>Lennart</firstname> | |
24 | <surname>Poettering</surname> | |
25 | <email>lennart@poettering.net</email> | |
26 | </author> | |
27 | </authorgroup> | |
28 | </refentryinfo> | |
29 | ||
30 | <refmeta> | |
31 | <refentrytitle>sd_watchdog_enabled</refentrytitle> | |
32 | <manvolnum>3</manvolnum> | |
33 | </refmeta> | |
34 | ||
35 | <refnamediv> | |
36 | <refname>sd_watchdog_enabled</refname> | |
37 | <refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose> | |
38 | </refnamediv> | |
39 | ||
40 | <refsynopsisdiv> | |
41 | <funcsynopsis> | |
42 | <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> | |
43 | ||
44 | <funcprototype> | |
45 | <funcdef>int <function>sd_watchdog_enabled</function></funcdef> | |
46 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
47 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> | |
48 | </funcprototype> | |
49 | </funcsynopsis> | |
50 | </refsynopsisdiv> | |
51 | ||
52 | <refsect1> | |
53 | <title>Description</title> | |
54 | <para><function>sd_watchdog_enabled()</function> may be called by | |
55 | a service to detect whether the service manager expects regular | |
56 | keep-alive watchdog notification events from it, and the timeout | |
57 | after which the manager will act on the service if it did not get | |
58 | such a notification.</para> | |
59 | ||
60 | <para>If the <varname>$WATCHDOG_USEC</varname> environment | |
61 | variable is set, and the <varname>$WATCHDOG_PID</varname> variable | |
62 | is unset or set to the PID of the current process, the service | |
63 | manager expects notifications from this process. The manager will | |
64 | usually terminate a service when it does not get a notification | |
65 | message within the specified time after startup and after each | |
66 | previous message. It is recommended that a daemon sends a | |
67 | keep-alive notification message to the service manager every half | |
68 | of the time returned here. Notification messages may be sent with | |
69 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
70 | with a message string of <literal>WATCHDOG=1</literal>.</para> | |
71 | ||
72 | <para>If the <parameter>unset_environment</parameter> parameter is | |
73 | non-zero, <function>sd_watchdog_enabled()</function> will unset | |
74 | the <varname>$WATCHDOG_USEC</varname> and | |
75 | <varname>$WATCHDOG_PID</varname> environment variables before | |
76 | returning (regardless of whether the function call itself | |
77 | succeeded or not). Those variables are no longer inherited by | |
78 | child processes. Further calls to | |
79 | <function>sd_watchdog_enabled()</function> will also return with | |
80 | zero.</para> | |
81 | ||
82 | <para>If the <parameter>usec</parameter> parameter is non-NULL, | |
83 | <function>sd_watchdog_enabled()</function> will write the timeout | |
84 | in µs for the watchdog logic to it.</para> | |
85 | ||
86 | <para>To enable service supervision with the watchdog logic, use | |
87 | <varname>WatchdogSec=</varname> in service files. See | |
88 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
89 | for details.</para> | |
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90 | |
91 | <para>Use | |
92 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
93 | to enable automatic watchdog support in | |
94 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>-based event loops.</para> | |
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95 | </refsect1> |
96 | ||
97 | <refsect1> | |
98 | <title>Return Value</title> | |
99 | ||
100 | <para>On failure, this call returns a negative errno-style error | |
101 | code. If the service manager expects watchdog keep-alive | |
102 | notification messages to be sent, > 0 is returned, otherwise 0 | |
103 | is returned. Only if the return value is > 0, the | |
104 | <parameter>usec</parameter> parameter is valid after the | |
105 | call.</para> | |
106 | </refsect1> | |
107 | ||
108 | <refsect1> | |
109 | <title>Notes</title> | |
110 | ||
111 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> | |
112 | ||
fa000db3 | 113 | <para>Internally, this function parses the |
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114 | <varname>$WATCHDOG_PID</varname> and |
115 | <varname>$WATCHDOG_USEC</varname> environment variable. The call | |
116 | will ignore these variables if <varname>$WATCHDOG_PID</varname> | |
117 | does not contain the PID of the current process, under the | |
118 | assumption that in that case, the variables were set for a | |
119 | different process further up the process tree.</para> | |
120 | </refsect1> | |
121 | ||
122 | <refsect1> | |
123 | <title>Environment</title> | |
124 | ||
125 | <variablelist class='environment-variables'> | |
126 | <varlistentry> | |
127 | <term><varname>$WATCHDOG_PID</varname></term> | |
128 | ||
129 | <listitem><para>Set by the system manager for supervised | |
130 | process for which watchdog support is enabled, and contains | |
131 | the PID of that process. See above for | |
132 | details.</para></listitem> | |
133 | </varlistentry> | |
134 | ||
135 | <varlistentry> | |
136 | <term><varname>$WATCHDOG_USEC</varname></term> | |
137 | ||
138 | <listitem><para>Set by the system manager for supervised | |
139 | process for which watchdog support is enabled, and contains | |
fa000db3 | 140 | the watchdog timeout in µs. See above for |
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141 | details.</para></listitem> |
142 | </varlistentry> | |
143 | </variablelist> | |
144 | </refsect1> | |
145 | ||
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146 | <refsect1> |
147 | <title>See Also</title> | |
148 | <para> | |
149 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
150 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
151 | <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
152 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
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153 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
154 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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155 | </para> |
156 | </refsect1> | |
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157 | |
158 | </refentry> |