1COLLECTD-PERL(5) collectd COLLECTD-PERL(5)
2
6 collectd-perl - Documentation of collectd's "perl plugin"
7
9 LoadPlugin perl
10 # ...
11 <Plugin perl>
12 IncludeDir "/path/to/perl/plugins"
13 BaseName "Collectd::Plugins"
14 EnableDebugger ""
15 LoadPlugin "FooBar"
16 <Plugin FooBar>
18 Foo "Bar"
19 </Plugin>
20 </Plugin>
21
23 The "perl plugin" embeds a Perl-interpreter into collectd and provides
24 an interface to collectd's plugin system. This makes it possible to
25 write plugins for collectd in Perl. This is a lot more efficient than
26 executing a Perl-script every time you want to read a value with the
27 "exec plugin" (see collectd-exec(5)) and provides a lot more
28 functionality, too.
29
31 LoadPlugin Plugin
32 Loads the Perl plugin Plugin. This does basically the same as use
33 would do in a Perl program. As a side effect, the first occurrence
34 of this option causes the Perl-interpreter to be initialized.
35 BaseName Name
37 Prepends Name:: to all plugin names loaded after this option. This
38 is provided for convenience to keep plugin names short. All Perl-
39 based plugins provided with the collectd distributions reside in
40 the "Collectd::Plugins" namespace.
41 <Plugin Name> block
43 This block may be used to pass on configuration settings to a Perl
44 plugin. The configuration is converted into a config-item data type
45 which is passed to the registered configuration callback. See below
46 for details about the config-item data type and how to register
47 callbacks.
48 The name identifies the callback. It is used literally and
50 independent of the BaseName setting.
51 EnableDebugger Package[=option,...]
53 Run collectd under the control of the Perl source debugger. If
54 Package is not the empty string, control is passed to the
55 debugging, profiling, or tracing module installed as
56 Devel::Package. A comma-separated list of options may be specified
57 after the "=" character. Please note that you may not leave out the
58 Package option even if you specify "". This is the same as using
59 the -d:Package command line option.
60 See perldebug for detailed documentation about debugging Perl.
62 This option does not prevent collectd from daemonizing, so you
64 should start collectd with the -f command line option. Else you
65 will not be able to use the command line driven interface of the
66 debugger.
67 IncludeDir Dir
69 Adds Dir to the @INC array. This is the same as using the -IDir
70 command line option or use lib Dir in the source code. Please note
71 that it only has effect on plugins loaded after this option.
72 RegisterLegacyFlush true|false
74 The "Perl plugin" used to register one flush callback (called
75 "perl") and call all Perl-based flush handlers when this callback
76 was called. Newer versions of the plugin wrap the Perl flush
77 handlers and register them directly with the daemon in addition to
78 the legacy "perl" callback. This allows to call specific Perl flush
79 handlers, but has the downside that flushing all plugins now calls
80 the Perl flush handlers twice (once directly and once via the
81 legacy callback). Unfortunately, removing the "perl" callback would
82 break backwards compatibility.
83 This option allows you to disable the legacy "perl" flush callback
85 if you care about the double call and don't call the "perl"
86 callback in your setup.
87
89 Writing your own plugins is quite simple. collectd manages plugins by
90 means of dispatch functions which call the appropriate callback
91 functions registered by the plugins. Any plugin basically consists of
92 the implementation of these callback functions and initializing code
93 which registers the functions with collectd. See the section "EXAMPLES"
94 below for a really basic example. The following types of callback
95 functions are known to collectd (all of them are optional):
96 configuration functions
98 This type of functions is called during configuration if an
99 appropriate Plugin block has been encountered. It is called once
100 for each Plugin block which matches the name of the callback as
101 provided with the plugin_register method - see below.
102 init functions
104 This type of functions is called once after loading the module and
105 before any calls to the read and write functions. It should be used
106 to initialize the internal state of the plugin (e. g. open sockets,
107 ...). If the return value evaluates to false, the plugin will be
108 disabled.
109 read functions
111 This type of function is used to collect the actual data. It is
112 called once per interval (see the Interval configuration option of
113 collectd). Usually it will call plugin_dispatch_values to dispatch
114 the values to collectd which will pass them on to all registered
115 write functions. If the return value evaluates to false the plugin
116 will be skipped for an increasing amount of time until it returns
117 true again.
118 write functions
120 This type of function is used to write the dispatched values. It is
121 called once for each call to plugin_dispatch_values.
122 flush functions
124 This type of function is used to flush internal caches of plugins.
125 It is usually triggered by the user only. Any plugin which caches
126 data before writing it to disk should provide this kind of callback
127 function.
128 log functions
130 This type of function is used to pass messages of plugins or the
131 daemon itself to the user.
132 notification function
134 This type of function is used to act upon notifications. In
135 general, a notification is a status message that may be associated
136 with a data instance. Usually, a notification is generated by the
137 daemon if a configured threshold has been exceeded (see the section
138 "THRESHOLD CONFIGURATION" in collectd.conf(5) for more details),
139 but any plugin may dispatch notifications as well.
140 shutdown functions
142 This type of function is called once before the daemon shuts down.
143 It should be used to clean up the plugin (e.g. close sockets, ...).
144 Any function (except log functions) may set the $@ variable to describe
146 errors in more detail. The message will be passed on to the user using
147 collectd's logging mechanism.
148 See the documentation of the plugin_register method in the section
150 "METHODS" below for the number and types of arguments passed to each
151 callback function. This section also explains how to register callback
152 functions with collectd.
153 To enable a plugin, copy it to a place where Perl can find it (i. e. a
155 directory listed in the @INC array) just as any other Perl plugin and
156 add an appropriate LoadPlugin option to the configuration file. After
157 restarting collectd you're done.
158
160 The following complex types are used to pass values between the Perl
161 plugin and collectd:
162 Config-Item
164 A config-item is one structure which keeps the information provided
165 in the configuration file. The array of children keeps one entry
166 for each configuration option. Each such entry is another config-
167 item structure, which may nest further if nested blocks are used.
168 {
170 key => key,
171 values => [ val1, val2, ... ],
172 children => [ { ... }, { ... }, ... ]
173 }
174 Data-Set
176 A data-set is a list of one or more data-sources. Each data-source
177 defines a name, type, min- and max-value and the data-set wraps
178 them up into one structure. The general layout looks like this:
179 [{
181 name => 'data_source_name',
182 type => DS_TYPE_COUNTER || DS_TYPE_GAUGE || DS_TYPE_DERIVE || DS_TYPE_ABSOLUTE,
183 min => value || undef,
184 max => value || undef
185 }, ...]
186 Value-List
188 A value-list is one structure which features an array of values and
189 fields to identify the values, i. e. time and host, plugin name and
190 plugin-instance as well as a type and type-instance. Since the
191 "type" is not included in the value-list but is passed as an extra
192 argument, the general layout looks like this:
193 {
195 values => [123, 0.5],
196 time => time (),
197 interval => plugin_get_interval (),
198 host => $hostname_g,
199 plugin => 'myplugin',
200 type => 'myplugin',
201 plugin_instance => '',
202 type_instance => ''
203 }
204 Notification
206 A notification is one structure defining the severity, time and
207 message of the status message as well as an identification of a
208 data instance. Also, it includes an optional list of user-defined
209 meta information represented as (name, value) pairs:
210 {
212 severity => NOTIF_FAILURE || NOTIF_WARNING || NOTIF_OKAY,
213 time => time (),
214 message => 'status message',
215 host => $hostname_g,
216 plugin => 'myplugin',
217 type => 'mytype',
218 plugin_instance => '',
219 type_instance => '',
220 meta => [ { name => <name>, value => <value> }, ... ]
221 }
222 Match-Proc
224 A match-proc is one structure storing the callbacks of a "match" of
225 the filter chain infrastructure. The general layout looks like
226 this:
227 {
229 create => 'my_create',
230 destroy => 'my_destroy',
231 match => 'my_match'
232 }
233 Target-Proc
235 A target-proc is one structure storing the callbacks of a "target"
236 of the filter chain infrastructure. The general layout looks like
237 this:
238 {
240 create => 'my_create',
241 destroy => 'my_destroy',
242 invoke => 'my_invoke'
243 }
244
246 The following functions provide the C-interface to Perl-modules. They
247 are exported by the ":plugin" export tag (see the section "EXPORTS"
248 below).
249 plugin_register (type, name, data)
251 Registers a callback-function or data-set.
252 type can be one of:
254 TYPE_CONFIG
256 TYPE_INIT
257 TYPE_READ
258 TYPE_WRITE
259 TYPE_FLUSH
260 TYPE_LOG
261 TYPE_NOTIF
262 TYPE_SHUTDOWN
263 TYPE_DATASET
264 name is the name of the callback-function or the type of the data-
266 set, depending on the value of type. (Please note that the type of
267 the data-set is the value passed as name here and has nothing to do
268 with the type argument which simply tells plugin_register what is
269 being registered.)
270 The last argument, data, is either a function name or an array-
272 reference. If type is TYPE_DATASET, then the data argument must be
273 an array-reference which points to an array of hashes. Each hash
274 describes one data-set. For the exact layout see Data-Set above.
275 Please note that there is a large number of predefined data-sets
276 available in the types.db file which are automatically registered
277 with collectd - see types.db(5) for a description of the format of
278 this file.
279 Note: Using plugin_register to register a data-set is deprecated.
281 Add the new type to a custom types.db(5) file instead. This
282 functionality might be removed in a future version of collectd.
283 If the type argument is any of the other types (TYPE_INIT,
285 TYPE_READ, ...) then data is expected to be a function name. If the
286 name is not prefixed with the plugin's package name collectd will
287 add it automatically. The interface slightly differs from the C
288 interface (which expects a function pointer instead) because Perl
289 does not support to share references to subroutines between
290 threads.
291 These functions are called in the various stages of the daemon (see
293 the section "WRITING YOUR OWN PLUGINS" above) and are passed the
294 following arguments:
295 TYPE_CONFIG
297 The only argument passed is config-item. See above for the
298 layout of this data type.
299 TYPE_INIT
301 TYPE_READ
302 TYPE_SHUTDOWN
303 No arguments are passed.
304 TYPE_WRITE
306 The arguments passed are type, data-set, and value-list. type
307 is a string. For the layout of data-set and value-list see
308 above.
309 TYPE_FLUSH
311 The arguments passed are timeout and identifier. timeout
312 indicates that only data older than timeout seconds is to be
313 flushed. identifier specifies which values are to be flushed.
314 TYPE_LOG
316 The arguments are log-level and message. The log level is small
317 for important messages and high for less important messages.
318 The least important level is LOG_DEBUG, the most important
319 level is LOG_ERR. In between there are (from least to most
320 important): LOG_INFO, LOG_NOTICE, and LOG_WARNING. message is
321 simply a string without a newline at the end.
322 TYPE_NOTIF
324 The only argument passed is notification. See above for the
325 layout of this data type.
326 plugin_unregister (type, plugin)
328 Removes a callback or data-set from collectd's internal list of
329 functions / datasets.
330 plugin_dispatch_values (value-list)
332 Submits a value-list to the daemon. If the data-set identified by
333 value-list->{type} is found (and the number of values matches the
334 number of data-sources) then the type, data-set and value-list is
335 passed to all write-callbacks that are registered with the daemon.
336 plugin_write ([plugins => ...][, datasets => ...], valuelists => ...)
338 Calls the write function of the given plugins with the provided
339 data sets and value lists. In contrast to plugin_dispatch_values,
340 it does not update collectd's internal cache and bypasses the
341 filter mechanism (see collectd.conf(5) for details). If the plugins
342 argument has been omitted, the values will be dispatched to all
343 registered write plugins. If the datasets argument has been
344 omitted, the required data sets are looked up according to the
345 "type" member in the appropriate value list. The value of all three
346 arguments may either be a single scalar or a reference to an array.
347 If the datasets argument has been specified, the number of data
348 sets has to equal the number of specified value lists.
349 plugin_flush ([timeout => timeout][, plugins => ...][, identifiers =>
351 ...])
352 Flush one or more plugins. timeout and the specified identifiers
353 are passed on to the registered flush-callbacks. If omitted, the
354 timeout defaults to "-1". The identifier defaults to the undefined
355 value. If the plugins argument has been specified, only named
356 plugins will be flushed. The value of the plugins and identifiers
357 arguments may either be a string or a reference to an array of
358 strings.
359 plugin_dispatch_notification (notification)
361 Submits a notification to the daemon which will then pass it to all
362 notification-callbacks that are registered.
363 plugin_log (log-level, message)
365 Submits a message of level log-level to collectd's logging
366 mechanism. The message is passed to all log-callbacks that are
367 registered with collectd.
368 ERROR, WARNING, NOTICE, INFO, DEBUG (message)
370 Wrappers around plugin_log, using LOG_ERR, LOG_WARNING, LOG_NOTICE,
371 LOG_INFO and LOG_DEBUG respectively as log-level.
372 plugin_get_interval ()
374 Returns the interval of the current plugin as a floating point
375 number in seconds. This value depends on the interval configured
376 within the "LoadPlugin perl" block or the global interval (see
377 collectd.conf(5) for details).
378 The following function provides the filter chain C-interface to Perl-
380 modules. It is exported by the ":filter_chain" export tag (see the
381 section "EXPORTS" below).
382 fc_register (type, name, proc)
384 Registers filter chain callbacks with collectd.
385 type may be any of:
387 FC_MATCH
389 FC_TARGET
390 name is the name of the match or target. By this name, the
392 callbacks are identified in the configuration file when specifying
393 a Match or Target block (see collectd.conf(5) for details).
394 proc is a hash reference. The hash includes up to three callbacks:
396 an optional constructor (create) and destructor (destroy) and a
397 mandatory match or invoke callback. match is called whenever
398 processing an appropriate match, while invoke is called whenever
399 processing an appropriate target (see the section "FILTER
400 CONFIGURATION" in collectd.conf(5) for details). Just like any
401 other callbacks, filter chain callbacks are identified by the
402 function name rather than a function pointer because Perl does not
403 support to share references to subroutines between threads. The
404 following arguments are passed to the callbacks:
405 create
407 The arguments passed are config-item and user-data. See above
408 for the layout of the config-item data-type. user-data is a
409 reference to a scalar value that may be used to store any
410 information specific to this particular instance. The daemon
411 does not care about this information at all. It's for the
412 plugin's use only.
413 destroy
415 The only argument passed is user-data which is a reference to
416 the user data initialized in the create callback. This callback
417 may be used to cleanup instance-specific information and
418 settings.
419 match, invoke
421 The arguments passed are data-set, value-list, meta and user-
422 data. See above for the layout of the data-set and value-list
423 data-types. meta is a pointer to an array of meta information,
424 just like the meta member of the notification data-type (see
425 above). user-data is a reference to the user data initialized
426 in the create callback.
427
429 $hostname_g
430 As the name suggests this variable keeps the hostname of the system
431 collectd is running on. The value might be influenced by the
432 Hostname or FQDNLookup configuration options (see collectd.conf(5)
433 for details).
434 $interval_g
436 This variable keeps the interval in seconds in which the read
437 functions are queried (see the Interval configuration option).
438 Note: This variable should no longer be used in favor of
440 "plugin_get_interval()" (see above). This function takes any
441 plugin-specific interval settings into account (see the "Interval"
442 option of "LoadPlugin" in collectd.conf(5) for details).
443 Any changes to these variables will be globally visible in collectd.
445
447 By default no symbols are exported. However, the following export tags
448 are available (:all will export all of them):
449 :plugin
451 plugin_register ()
452 plugin_unregister ()
453 plugin_dispatch_values ()
454 plugin_flush ()
455 plugin_flush_one ()
456 plugin_flush_all ()
457 plugin_dispatch_notification ()
458 plugin_log ()
459 :types
460 TYPE_CONFIG
461 TYPE_INIT
462 TYPE_READ
463 TYPE_WRITE
464 TYPE_FLUSH
465 TYPE_SHUTDOWN
466 TYPE_LOG
467 TYPE_DATASET
468 :ds_types
469 DS_TYPE_COUNTER
470 DS_TYPE_GAUGE
471 DS_TYPE_DERIVE
472 DS_TYPE_ABSOLUTE
473 :log
474 ERROR ()
475 WARNING ()
476 NOTICE ()
477 INFO ()
478 DEBUG ()
479 LOG_ERR
480 LOG_WARNING
481 LOG_NOTICE
482 LOG_INFO
483 LOG_DEBUG
484 :filter_chain
485 fc_register
486 FC_MATCH_NO_MATCH
487 FC_MATCH_MATCHES
488 FC_TARGET_CONTINUE
489 FC_TARGET_STOP
490 FC_TARGET_RETURN
491 :fc_types
492 FC_MATCH
493 FC_TARGET
494 :notif
495 NOTIF_FAILURE
496 NOTIF_WARNING
497 NOTIF_OKAY
498 :globals
499 $hostname_g
500 $interval_g
501
503 Any Perl plugin will start similar to:
504 package Collectd::Plugins::FooBar;
506 use strict;
508 use warnings;
509 use Collectd qw( :all );
511 A very simple read function might look like:
513 sub foobar_read
515 {
516 my $vl = { plugin => 'foobar', type => 'gauge' };
517 $vl->{'values'} = [ rand(42) ];
518 plugin_dispatch_values ($vl);
519 return 1;
520 }
521 A very simple write function might look like:
523 sub foobar_write
525 {
526 my ($type, $ds, $vl) = @_;
527 for (my $i = 0; $i < scalar (@$ds); ++$i) {
528 print "$vl->{'plugin'} ($vl->{'type'}): $vl->{'values'}->[$i]\n";
529 }
530 return 1;
531 }
532 A very simple match callback might look like:
534 sub foobar_match
536 {
537 my ($ds, $vl, $meta, $user_data) = @_;
538 if (matches($ds, $vl)) {
539 return FC_MATCH_MATCHES;
540 } else {
541 return FC_MATCH_NO_MATCH;
542 }
543 }
544 To register those functions with collectd:
546 plugin_register (TYPE_READ, "foobar", "foobar_read");
548 plugin_register (TYPE_WRITE, "foobar", "foobar_write");
549 fc_register (FC_MATCH, "foobar", "foobar_match");
551 See the section "DATA TYPES" above for a complete documentation of the
553 data types used by the read, write and match functions.
554
556 • Please feel free to send in new plugins to collectd's mailing list
557 at <collectd at collectd.org> for review and, possibly, inclusion
558 in the main distribution. In the latter case, we will take care of
559 keeping the plugin up to date and adapting it to new versions of
560 collectd.
561 Before submitting your plugin, please take a look at
563 <http://collectd.org/dev-info.shtml>.
564
566 • collectd is heavily multi-threaded. Each collectd thread accessing
567 the perl plugin will be mapped to a Perl interpreter thread (see
568 threads(3perl)). Any such thread will be created and destroyed
569 transparently and on-the-fly.
570 Hence, any plugin has to be thread-safe if it provides several
572 entry points from collectd (i. e. if it registers more than one
573 callback or if a registered callback may be called more than once
574 in parallel). Please note that no data is shared between threads by
575 default. You have to use the threads::shared module to do so.
576 • Each function name registered with collectd has to be available
578 before the first thread has been created (i. e. basically at
579 compile time). This basically means that hacks (yes, I really
580 consider this to be a hack) like "*foo = \&bar; plugin_register
581 (TYPE_READ, "plugin", "foo");" most likely will not work. This is
582 due to the fact that the symbol table is not shared across
583 different threads.
584 • Each plugin is usually only loaded once and kept in memory for
586 performance reasons. Therefore, END blocks are only executed once
587 when collectd shuts down. You should not rely on END blocks anyway
588 - use shutdown functions instead.
589 • The perl plugin exports the internal API of collectd which is
591 considered unstable and subject to change at any time. We try hard
592 to not break backwards compatibility in the Perl API during the
593 life cycle of one major release. However, this cannot be
594 guaranteed at all times. Watch out for warnings dispatched by the
595 perl plugin after upgrades.
596
598 collectd(1), collectd.conf(5), collectd-exec(5), types.db(5), perl(1),
599 threads(3perl), threads::shared(3perl), perldebug(1)
600
602 The "perl plugin" has been written by Sebastian Harl
603 <sh at tokkee.org>.
604 This manpage has been written by Florian Forster <octo at collectd.org>
606 and Sebastian Harl <sh at tokkee.org>.
6075.12.0 2020-09-03 COLLECTD-PERL(5)