]>
Commit | Line | Data |
---|---|---|
09812eb7 LP |
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"> |
09812eb7 LP |
4 | |
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
09812eb7 LP |
7 | --> |
8 | ||
6a70f3aa | 9 | <refentry id="sd_watchdog_enabled" |
798d3a52 ZJS |
10 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
11 | ||
12 | <refentryinfo> | |
13 | <title>sd_watchdog_enabled</title> | |
14 | <productname>systemd</productname> | |
15 | ||
16 | <authorgroup> | |
17 | <author> | |
18 | <contrib>Developer</contrib> | |
19 | <firstname>Lennart</firstname> | |
20 | <surname>Poettering</surname> | |
21 | <email>lennart@poettering.net</email> | |
22 | </author> | |
23 | </authorgroup> | |
24 | </refentryinfo> | |
25 | ||
26 | <refmeta> | |
27 | <refentrytitle>sd_watchdog_enabled</refentrytitle> | |
28 | <manvolnum>3</manvolnum> | |
29 | </refmeta> | |
30 | ||
31 | <refnamediv> | |
32 | <refname>sd_watchdog_enabled</refname> | |
33 | <refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose> | |
34 | </refnamediv> | |
35 | ||
36 | <refsynopsisdiv> | |
37 | <funcsynopsis> | |
38 | <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> | |
39 | ||
40 | <funcprototype> | |
41 | <funcdef>int <function>sd_watchdog_enabled</function></funcdef> | |
42 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
43 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> | |
44 | </funcprototype> | |
45 | </funcsynopsis> | |
46 | </refsynopsisdiv> | |
47 | ||
48 | <refsect1> | |
49 | <title>Description</title> | |
50 | <para><function>sd_watchdog_enabled()</function> may be called by | |
51 | a service to detect whether the service manager expects regular | |
52 | keep-alive watchdog notification events from it, and the timeout | |
53 | after which the manager will act on the service if it did not get | |
54 | such a notification.</para> | |
55 | ||
56 | <para>If the <varname>$WATCHDOG_USEC</varname> environment | |
57 | variable is set, and the <varname>$WATCHDOG_PID</varname> variable | |
58 | is unset or set to the PID of the current process, the service | |
59 | manager expects notifications from this process. The manager will | |
60 | usually terminate a service when it does not get a notification | |
61 | message within the specified time after startup and after each | |
62 | previous message. It is recommended that a daemon sends a | |
63 | keep-alive notification message to the service manager every half | |
64 | of the time returned here. Notification messages may be sent with | |
65 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
66 | with a message string of <literal>WATCHDOG=1</literal>.</para> | |
67 | ||
68 | <para>If the <parameter>unset_environment</parameter> parameter is | |
69 | non-zero, <function>sd_watchdog_enabled()</function> will unset | |
70 | the <varname>$WATCHDOG_USEC</varname> and | |
71 | <varname>$WATCHDOG_PID</varname> environment variables before | |
72 | returning (regardless of whether the function call itself | |
73 | succeeded or not). Those variables are no longer inherited by | |
74 | child processes. Further calls to | |
75 | <function>sd_watchdog_enabled()</function> will also return with | |
76 | zero.</para> | |
77 | ||
78 | <para>If the <parameter>usec</parameter> parameter is non-NULL, | |
79 | <function>sd_watchdog_enabled()</function> will write the timeout | |
80 | in µs for the watchdog logic to it.</para> | |
81 | ||
82 | <para>To enable service supervision with the watchdog logic, use | |
83 | <varname>WatchdogSec=</varname> in service files. See | |
84 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
85 | for details.</para> | |
dc83f27a LP |
86 | |
87 | <para>Use | |
88 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
89 | to enable automatic watchdog support in | |
90 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>-based event loops.</para> | |
798d3a52 ZJS |
91 | </refsect1> |
92 | ||
93 | <refsect1> | |
94 | <title>Return Value</title> | |
95 | ||
96 | <para>On failure, this call returns a negative errno-style error | |
97 | code. If the service manager expects watchdog keep-alive | |
98 | notification messages to be sent, > 0 is returned, otherwise 0 | |
99 | is returned. Only if the return value is > 0, the | |
100 | <parameter>usec</parameter> parameter is valid after the | |
101 | call.</para> | |
102 | </refsect1> | |
103 | ||
104 | <refsect1> | |
105 | <title>Notes</title> | |
106 | ||
107 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> | |
108 | ||
fa000db3 | 109 | <para>Internally, this function parses the |
798d3a52 ZJS |
110 | <varname>$WATCHDOG_PID</varname> and |
111 | <varname>$WATCHDOG_USEC</varname> environment variable. The call | |
112 | will ignore these variables if <varname>$WATCHDOG_PID</varname> | |
113 | does not contain the PID of the current process, under the | |
114 | assumption that in that case, the variables were set for a | |
115 | different process further up the process tree.</para> | |
116 | </refsect1> | |
117 | ||
118 | <refsect1> | |
119 | <title>Environment</title> | |
120 | ||
121 | <variablelist class='environment-variables'> | |
122 | <varlistentry> | |
123 | <term><varname>$WATCHDOG_PID</varname></term> | |
124 | ||
125 | <listitem><para>Set by the system manager for supervised | |
126 | process for which watchdog support is enabled, and contains | |
127 | the PID of that process. See above for | |
128 | details.</para></listitem> | |
129 | </varlistentry> | |
130 | ||
131 | <varlistentry> | |
132 | <term><varname>$WATCHDOG_USEC</varname></term> | |
133 | ||
134 | <listitem><para>Set by the system manager for supervised | |
135 | process for which watchdog support is enabled, and contains | |
fa000db3 | 136 | the watchdog timeout in µs. See above for |
798d3a52 ZJS |
137 | details.</para></listitem> |
138 | </varlistentry> | |
139 | </variablelist> | |
140 | </refsect1> | |
141 | ||
798d3a52 ZJS |
142 | <refsect1> |
143 | <title>See Also</title> | |
144 | <para> | |
145 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
146 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
147 | <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
148 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
dc83f27a LP |
149 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
150 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
798d3a52 ZJS |
151 | </para> |
152 | </refsect1> | |
09812eb7 LP |
153 | |
154 | </refentry> |