1Munin::Plugin(3) User Contributed Perl Documentation Munin::Plugin(3)
2
6 Munin::Plugin - Utility functions for Perl Munin plugins.
7 Usage
9 use lib $ENV{'MUNIN_LIBDIR'};
10 use Munin::Plugin;
11 If your Munin installation predates the MUNIN_* environment variables
13 (introduced in 1.3.3) you can put this in your plugin configuration:
14 [*]
16 env.MUNIN_PLUGSTATE /var/lib/munin-node/plugin-state
17 env.MUNIN_LIBDIR /usr/share/munin
18 IF, indeed that is the munin plugin state directory. The default
20 install directory for Munin::Plugin is in Perl's module search path,
21 the "use lib" is there for the cases where this is not so, and the
22 variable needs to be set to stop Perl from complaining.
23 The module exports these functions: clean_fieldname, set_state_name,
25 save_state, restore_state, tail_open, tail_close.
26 Variables
28 The module instantiates a number of variables in the $Munin::Plugin
29 scope. None of these are exported, and they must be referenced by the
30 full names shown here.
31 $Munin::Plugin::me
33 The name of the plugin without any prefixing directory names and so on.
35 Same as "basename $0" in a shell. It is a very good idea to use this
36 in warning and/or error messages so that the logs show clearly what
37 plugin the error message comes from.
38 $Munin::Plugin::pluginstatedir
40 Identical to the environment variable MUNIN_PLUGSTATE (available since
42 Munin 1.3.3)
43 You can use this if you need to save several different state files.
45 But there is also a function to change the state file name so the state
46 file support functions can be used for several state files.
47 If its value cannot be determined the plugin will be aborted at once
49 with an explanatory message. The most likely causes are:
50 • You are running the plugin directly and not from munin-node or
52 munin-run;
53 • Your munin-node is too old;
55 • munin-node was installed incorrectly.
57 The two last points can be worked around by the plugin configuration
59 shown at the beginning of this document.
60 $Munin::Plugin::statefile
62 The automatically calculated name for the plugins state file. The name
64 is supplied by munin-node or munin-run (in the MUNIN_STATEFILE
65 environment variable). The file name contains the plugin name and the
66 IP address of the munin-master the node is talking to (munin-run leaves
67 the master part blank). This enables stateful plugins that calculate
68 gauges and assume a 5 minute run interval to work correctly in setups
69 with multiple masters (this is not a uncommon way to set up Munin).
70 To change the value of this please use the set_state_name($) procedure
72 (see below).
73 $Munin::Plugin::DEBUG
75 Set to true if the plugin should emit debug output. There are some
77 (but not many) debug print statements in the Module as well, which all
78 obey this variable. Set from the MUNIN_DEBUG environment variable.
79 Defaults to false (0).
80 Functions
82 $fieldname = clean_fieldname($input_fieldname)
83 Munin plugin field names are restricted with regards to what characters
85 they may use: The characters must be "[a-zA-Z0-9_]", while the first
86 character must be "[a-zA-Z_]". To satisfy these demands the function
87 replaces illegal characters with a '_'.
88 See also <http://munin-monitoring.org/wiki/notes_on_datasource_names>
90 set_state_name($statefile_name)
92 Override the default statefile name. This only modifies the filename
94 part, not the directory name. The function unconditionally appends
95 "-$MUNIN_MASTER_IP" to the file name to support multiple masters as
96 described in the documentation for the statefile variable (above).
97 Calling this function is not normally needed and is not recommended.
99 save_state(@state_vector)
101 Save the passed state vector to the state file appropriate for the
103 plugin. The state vector should contain only strings (or numbers), and
104 absolutely no objects or references. The strings may contain newlines
105 without ill effect.
106 If the file cannot be opened for writing the plugin will be aborted.
108 The state file name is determined automatically based on the name of
110 the process we're running as. See $Munin::Plugin::me,
111 $Munin::Plugin::statefile and set_state_name above about the file name.
112 The file will contain a starting line with a magic number so that the
114 library can see the difference between an actual state file and a file
115 containing rubbish. Currently this magic number is
116 '%MUNIN-STATE1.0\n'. Files with this magic number will contain the
117 vector verbatim with \r, \n and % URL encoded.
118 The function takes security precautions, like protesting fatally if the
120 state file is a symbolic link (symbolic link overwriting can have
121 unfortunate security ramifications).
122 @state_vector = restore_state()
124 Read state from the state file written by save_state(@). If everything
126 is OK the state vector will be returned.
127 undef will be returned if the file cannot be opened. Likewise if it
129 does not have a recognized magic number (in this case a warning will
130 also be printed, which will appear in the munin-node logs).
131 ($warning, $critical) = get_thresholds($field, [$warning_env,
133 [$critical_env]])
134 Look up the thresholds for the specified field from the environment
136 variables named after the field: "$field_warning" and
137 "$field_critical". Return their values. If there are no
138 $field_warning or $field_critical values then look for the variables
139 "warning" and "critical" and return those values if any.
140 If the second and/or third arguments are specified then they will be
142 used to specify the name of variables giving the the warning and
143 critical levels.
144 If no values are found for a threshold then undef is returned.
146 print_thresholds($field, [$warning_env, [$critical_env]])
148 If $field has warning or critical thresholds set for it, prints them in
150 the default fashion (eg. 'field.warning 42').
151 See get_thresholds for an explanation of the arguments.
153 adjust_threshold($threshold, $base)
155 If $threshold contains % signs, return a new threshold with adjusted
157 values for these percentages against $base.
158 ($file_handle,$rotated) = tail_open($file_name, $position)
160 Open the file and seek to the given position. If this position is
162 beyond the end of the file the function assumes that the file has been
163 rotated, and the file position will be at the start of the file.
164 If the file is opened OK the function returns a tuple consisting of the
166 file handle and a file rotation indicator. $rotated will be 1 if the
167 file has been rotated and 0 otherwise. Also, if the file was rotated a
168 warning is printed (only in debug mode, this can be found in the munin-
169 node log or seen in the terminal when using munin-run).
170 At this point the plugin can read from the file with <$file_handle> in
172 loop as usual until EOF is encountered.
173 If the file cannot be stat'ed "(undef,undef)" is returned. If the file
175 cannot be opened for reading the plugin is aborted with a error in the
176 interest of error-obviousness.
177 $position = tail_close($file_handle)
179 Close the the file and return the current position in the file. This
181 position can be stored in a state file until the next time the plugin
182 runs.
183 If the "close" system call fails, a warning will be printed (which can
185 be found in the munin-node log or seen when using munin-run).
186 $string = scaleNumber($number, $unit, $ifZero, $format);
188 Returns a string representation of the given number scaled in SI
190 prefixes such as G(iga), M(ega), and k(ilo), m(illi), u (for micro) and
191 so on for magnitudes from 10^-24 to 10^24.
192 The $unit is the base unit for the number and is appended to the
194 prefix.
195 The contents of $ifZero is used if the number is 0 (smaller than
197 10^-26), instead of any other string. In some contexts "" (empty
198 string) is most appropriate and sometimes "0" without any scale or
199 prefix is more appropriate.
200 $format can be any valid Perl printf format string. The default is
202 "%.1f%s%s".
203 The $format may be specified as a whole string such as "The interface
205 speed is %.1f%s%s.". In that case, $ifZero could be set to "The
206 interface is down" -- some equipment uses an interface speed of 0 for a
207 downed interface, and some don't.
208 need_multigraph()
210 Should be called at the top of all multigraph plugins.
212 Checks the current environment, and exits with appropriate output if it
214 doesn't support multigraph plugins.
215 Testing
217 There is some test stuff in this module.
219 Test like this:
221 MUNIN_PLUGSTATE=/var/lib/munin-node/plugin-state -e 'require "Plugin.pm.in"; Munin::Plugin::_test;' -- or something.
222 sub _test () {
224 my $pos;
225 my $fh;
226 my $reset;
227 warn "Testing tail and state file. Press ^C to stop\n";
229 do {
231 $pos = undef;
232 ($pos) = restore_state();
234 $pos = 0 unless defined($pos);
235 ($fh,$reset) = tail_open('/var/log/messages',$pos);
237 while (<$fh>) {
238 print;
239 }
240 $pos = tail_close($fh);
241 print "**Position is $pos\n";
242 save_state($pos);
243 } while sleep 1;
244 }
245perl v5.36.0 2022-07-24 Munin::Plugin(3)