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
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
|
<?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">
<!--
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd_watchdog_enabled">
<refentryinfo>
<title>sd_watchdog_enabled</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</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>const 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 <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). Further calls to
<function>sd_watchdog_enabled()</function> will then
return with zero, but the variable is no longer
inherited by child processes.</para>
<para>If the <parameter>usec</parameter> parameter is
non-NULL, <function>sd_watchdog_enabled()</function>
will return the timeout in µs for the watchdog
logic. The service manager will usually terminate a
service when it did 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>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>
</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>
<para>These APIs are implemented as a shared library,
which can be compiled and linked to with the
<constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
<para>Internally, this functions parses the
<varname>$WATCHDOG_PID</varname> and
<varname>$WATCHDOG_USEC</varname> environment
variable. The call will ignore these variables if
<varname>$WATCHDOG_PID</varname> does containe the PID
of the current process, under the assumption that in
that case, the variables were set for a different
process further up the process tree.</para>
</refsect1>
<refsect1>
<title>Environment</title>
<variablelist class='environment-variables'>
<varlistentry>
<term><varname>$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>
</para>
</refsect1>
</refentry>
|
