1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
|
<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
-->
<refentry id="sd_watchdog_enabled"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_watchdog_enabled</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_watchdog_enabled</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_watchdog_enabled</refname>
<refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_watchdog_enabled</function></funcdef>
<paramdef>int <parameter>unset_environment</parameter></paramdef>
<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_watchdog_enabled()</function> may be called by
a service to detect whether the service manager expects regular
keep-alive watchdog notification events from it, and the timeout
after which the manager will act on the service if it did not get
such a notification.</para>
<para>If the <varname>$WATCHDOG_USEC</varname> environment
variable is set, and the <varname>$WATCHDOG_PID</varname> variable
is unset or set to the PID of the current process, the service
manager expects notifications from this process. The manager will
usually terminate a service when it does not get a notification
message within the specified time after startup and after each
previous message. It is recommended that a daemon sends a
keep-alive notification message to the service manager every half
of the time returned here. Notification messages may be sent with
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
with a message string of <literal>WATCHDOG=1</literal>.</para>
<para>If the <parameter>unset_environment</parameter> parameter is
non-zero, <function>sd_watchdog_enabled()</function> will unset
the <varname>$WATCHDOG_USEC</varname> and
<varname>$WATCHDOG_PID</varname> environment variables before
returning (regardless of whether the function call itself
succeeded or not). Those variables are no longer inherited by
child processes. Further calls to
<function>sd_watchdog_enabled()</function> will also return with
zero.</para>
<para>If the <parameter>usec</parameter> parameter is non-NULL,
<function>sd_watchdog_enabled()</function> will write the timeout
in µs for the watchdog logic to it.</para>
<para>To enable service supervision with the watchdog logic, use
<varname>WatchdogSec=</varname> in service files. See
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details.</para>
<para>Use
<citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
to enable automatic watchdog support in
<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>-based event loops.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On failure, this call returns a negative errno-style error
code. If the service manager expects watchdog keep-alive
notification messages to be sent, > 0 is returned, otherwise 0
is returned. Only if the return value is > 0, the
<parameter>usec</parameter> parameter is valid after the
call.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
<para>Internally, this function parses the
<varname>$WATCHDOG_PID</varname> and
<varname>$WATCHDOG_USEC</varname> environment variable. The call
will ignore these variables if <varname>$WATCHDOG_PID</varname>
does not contain the PID of the current process, under the
assumption that in that case, the variables were set for a
different process further up the process tree.</para>
</refsect1>
<refsect1>
<title>Environment</title>
<variablelist class='environment-variables'>
<varlistentry>
<term><varname>$WATCHDOG_PID</varname></term>
<listitem><para>Set by the system manager for supervised
process for which watchdog support is enabled, and contains
the PID of that process. See above for
details.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>$WATCHDOG_USEC</varname></term>
<listitem><para>Set by the system manager for supervised
process for which watchdog support is enabled, and contains
the watchdog timeout in µs. See above for
details.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
|
GitWeb