Munin::Plugin(3) User Contributed Perl Documentation Munin::Plugin(3)NAMEMunin::Plugin - Utility functions for Perl Munin plugins.
Usage
use lib $ENV{'MUNIN_LIBDIR'};
use Munin::Plugin;
If your Munin installation predates the MUNIN_* environment variables
(introduced in 1.3.3) you can put this in your plugin configuration:
[*]
env.MUNIN_PLUGSTATE /var/lib/munin-node/plugin-state
env.MUNIN_LIBDIR /usr/share/munin
IF, indeed that is the munin plugin state directory. The default
install directory for Munin::Plugin is in Perl's module search path,
the "use lib" is there for the cases where this is not so, and the
variable needs to be set to stop Perl from complaining.
The module exports these functions: clean_fieldname, set_state_name,
save_state, restore_state, tail_open, tail_close.
Variables
The module instantiates a number of variables in the $Munin::Plugin
scope. None of these are exported, and they must be referenced by the
full names shown here.
$Munin::Plugin::me
The name of the plugin without any prefixing directory names and so on.
Same as "basename $0" in a shell. It is a very good idea to use this
in warning and/or error messages so that the logs show clearly what
plugin the error message comes from.
$Munin::Plugin::pluginstatedir
Identical to the environment variable MUNIN_PLUGSTATE (available since
Munin 1.3.3)
You can use this if you need to save several different state files.
But there is also a function to change the state file name so the state
file support functions can be used for several state files.
If its value cannot be determined the plugin will be aborted at once
with an explanatory message. The most likely causes are:
· You are running the plugin directly and not from munin-node or
munin-run;
· Your munin-node is too old;
· munin-node was installed incorrectly.
The two last points can be worked around by the plugin configuration
shown at the beginning of this document.
$Munin::Plugin::statefile
The automatically calculated name for the plugins state file. The name
is supplied by munin-node or munin-run (in the MUNIN_STATEFILE
environment variable). The file name contains the plugin name and the
IP address of the munin-master the node is talking to (munin-run leaves
the master part blank). This enables stateful plugins that calculate
gauges and assume a 5 minute run interval to work correctly in setups
with multiple masters (this is not a uncommon way to set up Munin).
To change the value of this please use the set_state_name($) procedure
(see below).
$Munin::Plugin::DEBUG
Set to true if the plugin should emit debug output. There are some
(but not many) debug print statements in the Module as well, which all
obey this variable. Set from the MUNIN_DEBUG environment variable.
Defaults to false (0).
Functions
$fieldname = clean_fieldname($input_fieldname)
Munin plugin field names are restricted with regards to what characters
they may use: The characters must be "[a-zA-Z0-9_]", while the first
character must be "[a-zA-Z_]". To satisfy these demands the function
replaces illegal characters with a '_'.
See also <http://munin-monitoring.org/wiki/notes_on_datasource_names>
set_state_name($statefile_name)
Override the default statefile name. This only modifies the filename
part, not the directory name. The function unconditionally appends
"-$MUNIN_MASTER_IP" to the file name to support multiple masters as
described in the documentation for the statefile variable (above).
Calling this function is not normally needed and is not recommended.
save_state(@state_vector)
Save the passed state vector to the state file appropriate for the
plugin. The state vector should contain only strings (or numbers), and
absolutely no objects or references. The strings may contain newlines
without ill effect.
If the file cannot be opened for writing the plugin will be aborted.
The state file name is determined automatically based on the name of
the process we're running as. See $Munin::Plugin::me,
$Munin::Plugin::statefile and set_state_name above about the file name.
The file will contain a starting line with a magic number so that the
library can see the difference between an actual state file and a file
containing rubbish. Currently this magic number is
'%MUNIN-STATE1.0\n'. Files with this magic number will contain the
vector verbatim with \r, \n and % URL encoded.
The function takes security precautions, like protesting fatally if the
state file is a symbolic link (symbolic link overwriting can have
unfortunate security ramifications).
@state_vector = restore_state()
Read state from the state file written by save_state(@). If everything
is OK the state vector will be returned.
undef will be returned if the file cannot be opened. Likewise if it
does not have a recognized magic number (in this case a warning will
also be printed, which will appear in the munin-node logs).
($warning, $critical) = get_thresholds($field, [$warning_env,
[$critical_env]])
Look up the thresholds for the specified field from the environment
variables named after the field: "$field_warning" and
"$field_critical". Return their values. If there are no
$field_warning or $field_critical values then look for the variables
"warning" and "critical" and return those values if any.
If the second and/or third arguments are specified then they will be
used to specify the name of variables giving the the warning and
critical levels.
If no values are found for a threshold then undef is returned.
print_thresholds($field, [$warning_env, [$critical_env]])
If $field has warning or critical thresholds set for it, prints them in
the default fashion (eg. 'field.warning 42').
See get_thresholds for an explanation of the arguments.
adjust_threshold($threshold, $base)
If $threshold contains % signs, return a new threshold with adjusted
values for these percentages against $base.
($file_handle,$rotated) = tail_open($file_name, $position)
Open the file and seek to the given position. If this position is
beyond the end of the file the function assumes that the file has been
rotated, and the file position will be at the start of the file.
If the file is opened OK the function returns a tuple consisting of the
file handle and a file rotation indicator. $rotated will be 1 if the
file has been rotated and 0 otherwise. Also, if the file was rotated a
warning is printed (this can be found in the munin-node log or seen in
the terminal when using munin-run).
At this point the plugin can read from the file with <$file_handle> in
loop as usual until EOF is encountered.
If the file cannot be stat'ed "(undef,undef)" is returned. If the file
cannot be opened for reading the plugin is aborted with a error in the
interest of error-obviousness.
$position = tail_close($file_handle)
Close the the file and return the current position in the file. This
position can be stored in a state file until the next time the plugin
runs.
If the "close" system call fails, a warning will be printed (which can
be found in the munin-node log or seen when using munin-run).
$string = scaleNumber($number, $unit, $ifZero, $format);
Returns a string representation of the given number scaled in SI
prefixes such as G(iga), M(ega), and k(ilo), m(illi), u (for micro) and
so on for magnitudes from 10^-24 to 10^24.
The $unit is the base unit for the number and is appended to the
prefix.
The contents of $ifZero is used if the number is 0 (smaller than
10^-26), instead of any other string. In some contexts "" (empty
string) is most appropriate and sometimes "0" without any scale or
prefix is more appropriate.
$format can be any valid Perl printf format string. The default is
"%.1f%s%s".
The $format may be specified as a whole string such as "The interface
speed is %.1f%s%s.". In that case, $ifZero could be set to "The
interface is down" -- some equipment uses an interface speed of 0 for a
downed interface, and some don't.
need_multigraph()
Should be called at the top of all multigraph plugins.
Checks the current environment, and exits with appropriate output if it
doesn't support multigraph plugins.
Testing
There is some test stuff in this module.
Test like this:
MUNIN_PLUGSTATE=/var/lib/munin-node/plugin-state -e 'require "Plugin.pm.in"; Munin::Plugin::_test;' -- or something.
sub _test () {
my $pos;
my $fh;
my $reset;
warn "Testing tail and state file. Press ^C to stop\n";
do {
$pos = undef;
($pos) = restore_state();
$pos = 0 unless defined($pos);
($fh,$reset) = tail_open('/var/log/messages',$pos);
while (<$fh>) {
print;
}
$pos = tail_close($fh);
print "**Position is $pos\n";
save_state($pos);
} while sleep 1;
}
perl v5.20.3 2016-02-19 Munin::Plugin(3)
