3 collectd-perl - Documentation of collectd's C<perl plugin>
10 IncludeDir "/path/to/perl/plugins"
11 BaseName "Collectd::Plugin"
18 The C<perl plugin> embeds a Perl-interpreter into collectd and provides an
19 interface to collectd's plugin system. This makes it possible to write plugins
20 for collectd in Perl. This is a lot more efficient than executing a
21 Perl-script every time you want to read a value with the C<exec plugin> (see
22 L<collectd-exec(5)>) and provides a lot more functionality, too.
24 Please note that this is still considered to be experimental and subject to
25 change between minor releases.
31 =item B<LoadPlugin> I<Plugin>
33 Loads the Perl plugin I<Plugin>. This does basically the same as B<use> would
34 do in a Perl program. As a side effect, the first occurrence of this option
35 causes the Perl-interpreter to be initialized.
37 =item B<BaseName> I<Name>
39 Prepends I<Name>B<::> to all plugin names loaded after this option. This is
40 provided for convenience to keep plugin names short.
42 =item B<EnableDebugger> I<Package>[=I<option>,...]
44 Run collectd under the control of the Perl source debugger. If I<Package> is
45 not the empty string, control is passed to the debugging, profiling, or
46 tracing module installed as Devel::I<Package>. A comma-separated list of
47 options may be specified after the "=" character. Please note that you may not
48 leave out the I<Package> option even if you specify B<"">. This is the same as
49 using the B<-d:Package> command line option.
51 See L<perldebug> for detailed documentation about debugging Perl.
53 =item B<IncludeDir> I<Dir>
55 Adds I<Dir> to the B<@INC> array. This is the same as using the B<-IDir>
56 command line option or B<use lib Dir> in the source code. Please note that it
57 only has effect on plugins loaded after this option.
61 =head1 WRITING YOUR OWN PLUGINS
63 Writing your own plugins is quite simply. collectd manages plugins by means of
64 B<dispatch functions> which call the appropriate B<callback functions>
65 registered by the plugins. Any plugin basically consists of the implementation
66 of these callback functions and initializing code which registers the
67 functions with collectd. See the section "EXAMPLES" below for a really basic
68 example. The following types of B<callback functions> are known to collectd
69 (all of these are optional):
75 This type of functions is called once after loading the module and before any
76 calls to the read and write functions. It should be used to initialize the
77 internal state of the plugin (e.E<nbsp>g. open sockets, ...). If the return
78 value evaluates to B<false>, the plugin will be disabled.
82 This type of function is used to collect the actual data. It is called once
83 per interval (see the B<Interval> configuration option of collectd). Usually
84 it will call B<plugin_dispatch_values> to dispatch the values to collectd
85 which will pass them on to all registered B<write functions>. If the return
86 value evaluates to B<false> the plugin will be skipped for an increasing
87 amount of time until it returns B<true> again.
91 This type of function is used to write the dispatched values. It is called
92 once for each call to B<plugin_dispatch_values>.
96 This type of function is used to pass messages of plugins or the daemon itself
99 =item shutdown functions
101 This type of function is called once before the daemon shuts down. It should
102 be used to clean up the plugin (e.g. close sockets, ...).
106 Any function may set the B<$@> variable to describe errors in more detail. The
107 message will be passed on to the user using collectd's logging mechanism.
109 See the documentation of the B<plugin_register> method in the section
110 "METHODS" below for the number and types of arguments passed to each
111 B<callback function>. This section also explains how to register B<callback
112 functions> with collectd.
114 To enable a plugin, copy it to a place where Perl can find it (i.E<nbsp>e. a
115 directory listed in the B<@INC> array) just as any other Perl plugin and add
116 an appropriate B<LoadPlugin> option to the configuration file. After
117 restarting collectd you're done.
121 The following complex types are used to pass values between the Perl plugin
128 A data-set is a list of one or more data-sources. Each data-source defines a
129 name, type, min- and max-value and the data-set wraps them up into one
130 structure. The general layout looks like this:
133 name => 'data_source_name',
134 type => DS_TYPE_COUNTER || DS_TYPE_GAUGE
135 min => value || undef,
136 max => value || undef
141 A value-list is one structure which features an array of values and fields to
142 identify the values, i.E<nbsp>e. time and host, plugin name and
143 plugin-instance as well as a type and type-instance. Since the "type" is not
144 included in the value-list but is passed as an extra argument, the general
145 layout looks like this:
148 values => [123, 0.5],
151 plugin => 'myplugin',
152 plugin_instance => '',
160 The following functions provide the C-interface to Perl-modules. They are
161 exported by the ":plugin" export tag (see the section "EXPORTS" below).
165 =item B<plugin_register> (I<type>, I<name>, I<data>)
167 Registers a callback-function or data-set.
169 I<type> can be one of:
187 I<name> is the name of the callback-function or the type of the data-set,
188 depending on the value of I<type>. (Please note that the type of the data-set
189 is the value passed as I<name> here and has nothing to do with the I<type>
190 argument which simply tells B<plugin_register> what is being registered.)
192 The last argument, I<data>, is either a function name or an array-reference.
193 If I<type> is B<TYPE_DATASET>, then the I<data> argument must be an
194 array-reference which points to an array of hashes. Each hash describes one
195 data-source. For the exact layout see B<Data-Set> above. Please note that
196 there is a large number of predefined data-sets available in the B<types.db>
197 file which are automatically registered with collectd.
199 If the I<type> argument is any of the other types (B<TYPE_INIT>, B<TYPE_READ>,
200 ...) then I<data> is expected to be a function name. If the name is not
201 prefixed with the plugin's package name collectd will add it automatically.
202 The interface slightly differs from the C interface (which expects a function
203 pointer instead) because Perl does not support to share references to
204 subroutines between threads.
206 These functions are called in the various stages of the daemon (see the
207 section "WRITING YOUR OWN PLUGINS" above) and are passed the following
218 No arguments are passed
222 The arguments passed are I<type>, I<data-set>, and I<value-list>. I<type> is a
223 string. For the layout of I<data-set> and I<value-list> see above.
227 The arguments are I<log-level> and I<message>. The log level is small for
228 important messages and high for less important messages. The least important
229 level is B<LOG_DEBUG>, the most important level is B<LOG_ERR>. In between there
230 are (from least to most important): B<LOG_INFO>, B<LOG_NOTICE>, and
231 B<LOG_WARNING>. I<message> is simply a string B<without> a newline at the end.
235 =item B<plugin_unregister> (I<type>, I<plugin>)
237 Removes a callback or data-set from collectd's internal list of
238 functionsE<nbsp>/ datasets.
240 =item B<plugin_dispatch_values> (I<type>, I<value-list>)
242 Submits a I<value-list> of type I<type> to the daemon. If the data-set I<type>
243 is found (and the number of values matches the number of data-sources) then the
244 type, data-set and value-list is passed to all write-callbacks that are
245 registered with the daemon.
247 =item B<plugin_log> (I<log-level>, I<message>)
249 Submits a I<message> of level I<log-level> to collectd's logging mechanism.
250 The message is passed to all log-callbacks that are registered with collectd.
252 =item B<ERROR>, B<WARNING>, B<NOTICE>, B<INFO>, B<DEBUG> (I<message>)
254 Wrappers around B<plugin_log>, using B<LOG_ERR>, B<LOG_WARNING>,
255 B<LOG_NOTICE>, B<LOG_INFO> and B<LOG_DEBUG> respectively as I<log-level>.
261 By default no symbols are exported. However, the following export tags are
262 available (B<:all> will export all of them):
270 =item B<plugin_register> ()
272 =item B<plugin_unregister> ()
274 =item B<plugin_dispatch_values> ()
276 =item B<plugin_log> ()
290 =item B<TYPE_SHUTDOWN>
300 =item B<DS_TYPE_COUNTER>
302 =item B<DS_TYPE_GAUGE>
336 Any Perl plugin will start similar to:
338 package Collectd::Plugins::FooBar;
343 use Collectd qw( :all );
345 A very simple read function will look like:
349 my $vl = { plugin => 'foobar' };
350 $vl->{'values'} = [ rand(42) ];
351 plugin_dispatch_values ('gauge', $vl);
355 A very simple write function will look like:
359 my ($type, $ds, $vl) = @_;
360 for (my $i = 0; $i < scalar (@$ds); ++$i) {
361 print "$vl->{'plugin'} ($vl->{'type'}): $vl->{'values'}->[$i]\n";
366 To register those functions with collectd:
368 plugin_register (TYPE_READ, "foobar", "foobar_read");
369 plugin_register (TYPE_WRITE, "foobar", "foobar_write");
371 See the section "DATA TYPES" above for a complete documentation of the data
372 types used by the read and write functions.
376 This plugin does not yet work correctly if collectd uses multiple threads.
377 Perl does not allow multiple threads to access a single interpreter at the
378 same time. As a temporary workaround you should use a single read thread only
379 (see collectd's B<ReadThread> configuration option).
391 The C<perl plugin> has been written by Sebastian Harl
392 E<lt>shE<nbsp>atE<nbsp>tokkee.orgE<gt>.
394 This manpage has been written by Florian Forster
395 E<lt>octoE<nbsp>atE<nbsp>verplant.orgE<gt> and Sebastian Harl
396 E<lt>shE<nbsp>atE<nbsp>tokkee.orgE<gt>.