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60f067b4 | 1 | <?xml version='1.0'?> <!--*-nxml-*--> |
bb4f798a | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
e735f4d4 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
a032b68d | 4 | <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
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5 | |
6 | <refentry id="sd_watchdog_enabled" | |
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7 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
8 | ||
9 | <refentryinfo> | |
10 | <title>sd_watchdog_enabled</title> | |
11 | <productname>systemd</productname> | |
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12 | </refentryinfo> |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>sd_watchdog_enabled</refentrytitle> | |
16 | <manvolnum>3</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>sd_watchdog_enabled</refname> | |
21 | <refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose> | |
22 | </refnamediv> | |
23 | ||
24 | <refsynopsisdiv> | |
25 | <funcsynopsis> | |
26 | <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> | |
27 | ||
28 | <funcprototype> | |
29 | <funcdef>int <function>sd_watchdog_enabled</function></funcdef> | |
30 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
31 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> | |
32 | </funcprototype> | |
33 | </funcsynopsis> | |
34 | </refsynopsisdiv> | |
35 | ||
36 | <refsect1> | |
37 | <title>Description</title> | |
38 | <para><function>sd_watchdog_enabled()</function> may be called by | |
39 | a service to detect whether the service manager expects regular | |
40 | keep-alive watchdog notification events from it, and the timeout | |
41 | after which the manager will act on the service if it did not get | |
42 | such a notification.</para> | |
43 | ||
44 | <para>If the <varname>$WATCHDOG_USEC</varname> environment | |
45 | variable is set, and the <varname>$WATCHDOG_PID</varname> variable | |
46 | is unset or set to the PID of the current process, the service | |
47 | manager expects notifications from this process. The manager will | |
48 | usually terminate a service when it does not get a notification | |
49 | message within the specified time after startup and after each | |
50 | previous message. It is recommended that a daemon sends a | |
51 | keep-alive notification message to the service manager every half | |
52 | of the time returned here. Notification messages may be sent with | |
53 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
54 | with a message string of <literal>WATCHDOG=1</literal>.</para> | |
55 | ||
56 | <para>If the <parameter>unset_environment</parameter> parameter is | |
57 | non-zero, <function>sd_watchdog_enabled()</function> will unset | |
58 | the <varname>$WATCHDOG_USEC</varname> and | |
59 | <varname>$WATCHDOG_PID</varname> environment variables before | |
60 | returning (regardless of whether the function call itself | |
61 | succeeded or not). Those variables are no longer inherited by | |
62 | child processes. Further calls to | |
63 | <function>sd_watchdog_enabled()</function> will also return with | |
64 | zero.</para> | |
65 | ||
a032b68d | 66 | <para>If the <parameter>usec</parameter> parameter is non-<constant>NULL</constant>, |
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67 | <function>sd_watchdog_enabled()</function> will write the timeout |
68 | in µs for the watchdog logic to it.</para> | |
69 | ||
70 | <para>To enable service supervision with the watchdog logic, use | |
71 | <varname>WatchdogSec=</varname> in service files. See | |
72 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
73 | for details.</para> | |
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74 | |
75 | <para>Use | |
76 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
77 | to enable automatic watchdog support in | |
78 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>-based event loops.</para> | |
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79 | </refsect1> |
80 | ||
81 | <refsect1> | |
82 | <title>Return Value</title> | |
83 | ||
84 | <para>On failure, this call returns a negative errno-style error | |
85 | code. If the service manager expects watchdog keep-alive | |
86 | notification messages to be sent, > 0 is returned, otherwise 0 | |
87 | is returned. Only if the return value is > 0, the | |
88 | <parameter>usec</parameter> parameter is valid after the | |
89 | call.</para> | |
90 | </refsect1> | |
91 | ||
92 | <refsect1> | |
93 | <title>Notes</title> | |
94 | ||
95 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> | |
96 | ||
2897b343 | 97 | <para>Internally, this function parses the |
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98 | <varname>$WATCHDOG_PID</varname> and |
99 | <varname>$WATCHDOG_USEC</varname> environment variable. The call | |
100 | will ignore these variables if <varname>$WATCHDOG_PID</varname> | |
101 | does not contain the PID of the current process, under the | |
102 | assumption that in that case, the variables were set for a | |
103 | different process further up the process tree.</para> | |
104 | </refsect1> | |
105 | ||
106 | <refsect1> | |
107 | <title>Environment</title> | |
108 | ||
109 | <variablelist class='environment-variables'> | |
110 | <varlistentry> | |
111 | <term><varname>$WATCHDOG_PID</varname></term> | |
112 | ||
113 | <listitem><para>Set by the system manager for supervised | |
114 | process for which watchdog support is enabled, and contains | |
115 | the PID of that process. See above for | |
116 | details.</para></listitem> | |
117 | </varlistentry> | |
118 | ||
119 | <varlistentry> | |
120 | <term><varname>$WATCHDOG_USEC</varname></term> | |
121 | ||
122 | <listitem><para>Set by the system manager for supervised | |
123 | process for which watchdog support is enabled, and contains | |
2897b343 | 124 | the watchdog timeout in µs. See above for |
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125 | details.</para></listitem> |
126 | </varlistentry> | |
127 | </variablelist> | |
128 | </refsect1> | |
129 | ||
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130 | <refsect1> |
131 | <title>See Also</title> | |
132 | <para> | |
133 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
134 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
135 | <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
136 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
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137 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
138 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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139 | </para> |
140 | </refsect1> | |
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141 | |
142 | </refentry> |