X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=src%2Fcollectd-perl.pod;h=8cdf08bb3b6807229bb4a985a5b01f74771f8378;hb=d5ad844588fcbcdcdd36a889c94ac33d36c1d52c;hp=3e15b88c60bbceac19d219404cfec1cb27c81e67;hpb=bd66a09b35da21dcb405650ae4587bf2ca811438;p=collectd.git

diff --git a/src/collectd-perl.pod b/src/collectd-perl.pod
index 3e15b88c..8cdf08bb 100644
--- a/src/collectd-perl.pod
+++ b/src/collectd-perl.pod
@@ -4,29 +4,139 @@ collectd-perl - Documentation of collectd's C<perl plugin>
 
 =head1 SYNOPSIS
 
-  # See collectd.conf(5)
   LoadPlugin perl
   # ...
   <Plugin perl>
     IncludeDir "/path/to/perl/plugins"
     BaseName "Collectd::Plugin"
+    EnableDebugger ""
     LoadPlugin "FooBar"
   </Plugin>
 
 =head1 DESCRIPTION
 
-The C<perl plugin> includes a Perl-interpreter in collectd and provides
-Perl-equivalents of the plugin-functions. This makes it possible to write
-plugins for collectd in Perl. This is a lot more efficient than executing a
+The C<perl plugin> embeds a Perl-interpreter into collectd and provides an
+interface to collectd's plugin system. This makes it possible to write plugins
+for collectd in Perl. This is a lot more efficient than executing a
 Perl-script every time you want to read a value with the C<exec plugin> (see
 L<collectd-exec(5)>) and provides a lot more functionality, too.
 
-Please note that this is still considered to be experimental and subject to
-change between minor releases.
+=head1 CONFIGURATION
+
+=over 4
+
+=item B<LoadPlugin> I<Plugin>
+
+Loads the Perl plugin I<Plugin>. This does basically the same as B<use> would
+do in a Perl program. As a side effect, the first occurrence of this option
+causes the Perl-interpreter to be initialized.
+
+=item B<BaseName> I<Name>
+
+Prepends I<Name>B<::> to all plugin names loaded after this option. This is
+provided for convenience to keep plugin names short.
+
+=item B<EnableDebugger> I<Package>[=I<option>,...]
+
+Run collectd under the control of the Perl source debugger. If I<Package> is
+not the empty string, control is passed to the debugging, profiling, or
+tracing module installed as Devel::I<Package>. A comma-separated list of
+options may be specified after the "=" character. Please note that you may not
+leave out the I<Package> option even if you specify B<"">. This is the same as
+using the B<-d:Package> command line option.
+
+See L<perldebug> for detailed documentation about debugging Perl.
+
+This option does not prevent collectd from daemonizing, so you should start
+collectd with the B<-f> command line option. Else you will not be able to use
+the command line driven interface of the debugger.
+
+=item B<IncludeDir> I<Dir>
+
+Adds I<Dir> to the B<@INC> array. This is the same as using the B<-IDir>
+command line option or B<use lib Dir> in the source code. Please note that it
+only has effect on plugins loaded after this option.
+
+=back
+
+=head1 WRITING YOUR OWN PLUGINS
+
+Writing your own plugins is quite simple. collectd manages plugins by means of
+B<dispatch functions> which call the appropriate B<callback functions>
+registered by the plugins. Any plugin basically consists of the implementation
+of these callback functions and initializing code which registers the
+functions with collectd. See the section "EXAMPLES" below for a really basic
+example. The following types of B<callback functions> are known to collectd
+(all of them are optional):
+
+=over 4
+
+=item init functions
+
+This type of functions is called once after loading the module and before any
+calls to the read and write functions. It should be used to initialize the
+internal state of the plugin (e.E<nbsp>g. open sockets, ...). If the return
+value evaluates to B<false>, the plugin will be disabled.
+
+=item read functions
+
+This type of function is used to collect the actual data. It is called once
+per interval (see the B<Interval> configuration option of collectd). Usually
+it will call B<plugin_dispatch_values> to dispatch the values to collectd
+which will pass them on to all registered B<write functions>. If the return
+value evaluates to B<false> the plugin will be skipped for an increasing
+amount of time until it returns B<true> again.
+
+=item write functions
+
+This type of function is used to write the dispatched values. It is called
+once for each call to B<plugin_dispatch_values>.
+
+=item flush functions
+
+This type of function is used to flush internal caches of plugins. It is
+usually triggered by the user only. Any plugin which caches data before
+writing it to disk should provide this kind of callback function.
+
+=item log functions
+
+This type of function is used to pass messages of plugins or the daemon itself
+to the user.
+
+=item notification function
+
+This type of function is used to act upon notifications. In general, a
+notification is a status message that may be associated with a data instance.
+Usually, a notification is generated by the daemon if a configured threshold
+has been exceeded (see the section "THRESHOLD CONFIGURATION" in
+L<collectd.conf(5)> for more details), but any plugin may dispatch
+notifications as well.
+
+=item shutdown functions
+
+This type of function is called once before the daemon shuts down. It should
+be used to clean up the plugin (e.g. close sockets, ...).
+
+=back
+
+Any function (except log functions) may set the B<$@> variable to describe
+errors in more detail. The message will be passed on to the user using
+collectd's logging mechanism.
+
+See the documentation of the B<plugin_register> method in the section
+"METHODS" below for the number and types of arguments passed to each
+B<callback function>. This section also explains how to register B<callback
+functions> with collectd.
+
+To enable a plugin, copy it to a place where Perl can find it (i.E<nbsp>e. a
+directory listed in the B<@INC> array) just as any other Perl plugin and add
+an appropriate B<LoadPlugin> option to the configuration file. After
+restarting collectd you're done.
 
 =head1 DATA TYPES
 
-There are two more complex types you need to know about:
+The following complex types are used to pass values between the Perl plugin
+and collectd:
 
 =over 4
 
@@ -38,7 +148,7 @@ structure. The general layout looks like this:
 
   [{
     name => 'data_source_name',
-    type => DS_TYPE_COUNTER || DS_TYPE_GAUGE
+    type => DS_TYPE_COUNTER || DS_TYPE_GAUGE,
     min  => value || undef,
     max  => value || undef
   }, ...]
@@ -46,27 +156,42 @@ structure. The general layout looks like this:
 =item Value-List
 
 A value-list is one structure which features an array of values and fields to
-identify the values, i. e. time and host, plugin name and plugin-instance as
-well as a type and type-instance. Since the "type" is not included in the
-value-list but is passed as an extra argument, the general layout looks like
-this:
+identify the values, i.E<nbsp>e. time and host, plugin name and
+plugin-instance as well as a type and type-instance. Since the "type" is not
+included in the value-list but is passed as an extra argument, the general
+layout looks like this:
 
   {
     values => [123, 0.5],
     time   => time (),
-    host   => 'localhost',
+    host   => $hostname_g,
     plugin => 'myplugin',
     plugin_instance => '',
     type_instance   => ''
   }
 
+=item Notification
+
+A notification is one structure defining the severity, time and message of the
+status message as well as an identification of a data instance:
+
+  {
+    severity => NOTIF_FAILURE || NOTIF_WARNING || NOTIF_OKAY,
+    time     => time (),
+    message  => 'status message',
+    host     => $hostname_g,
+    plugin   => 'myplugin',
+    type     => 'mytype',
+    plugin_instance => '',
+    type_instance   => ''
+  }
+
 =back
 
 =head1 METHODS
 
 The following functions provide the C-interface to Perl-modules. They are
-automatically exported into the module's namespace. You don't need to C<use>
-any special Modules to access them.
+exported by the ":plugin" export tag (see the section "EXPORTS" below).
 
 =over 4
 
@@ -84,8 +209,12 @@ I<type> can be one of:
 
 =item TYPE_WRITE
 
+=item TYPE_FLUSH
+
 =item TYPE_LOG
 
+=item TYPE_NOTIF
+
 =item TYPE_SHUTDOWN
 
 =item TYPE_DATASET
@@ -97,14 +226,23 @@ depending on the value of I<type>. (Please note that the type of the data-set
 is the value passed as I<name> here and has nothing to do with the I<type>
 argument which simply tells B<plugin_register> what is being registered.)
 
-The last argument, I<data>, is either a function- or an array-reference. If
-I<type> is B<TYPE_DATASET>, then the I<data> argument must be an
+The last argument, I<data>, is either a function name or an array-reference.
+If I<type> is B<TYPE_DATASET>, then the I<data> argument must be an
 array-reference which points to an array of hashes. Each hash describes one
-data-source. For the exact layout see B<Data-Set> above.
+data-set. For the exact layout see B<Data-Set> above. Please note that
+there is a large number of predefined data-sets available in the B<types.db>
+file which are automatically registered with collectd - see L<types.db(5)> for
+a description of the format of this file.
 
 If the I<type> argument is any of the other types (B<TYPE_INIT>, B<TYPE_READ>,
-...) then I<data> is expected to be a function reference. These functions are
-called in the various stages of the daemon and are passed the following
+...) then I<data> is expected to be a function name. If the name is not
+prefixed with the plugin's package name collectd will add it automatically.
+The interface slightly differs from the C interface (which expects a function
+pointer instead) because Perl does not support to share references to
+subroutines between threads.
+
+These functions are called in the various stages of the daemon (see the
+section "WRITING YOUR OWN PLUGINS" above) and are passed the following
 arguments:
 
 =over 4
@@ -115,13 +253,18 @@ arguments:
 
 =item TYPE_SHUTDOWN
 
-No arguments are passed
+No arguments are passed.
 
 =item TYPE_WRITE
 
 The arguments passed are I<type>, I<data-set>, and I<value-list>. I<type> is a
 string. For the layout of I<data-set> and I<value-list> see above.
 
+=item TYPE_FLUSH
+
+The only argument passed is I<timeout> which indicates that only data older
+than I<timeout> seconds is to be flushed.
+
 =item TYPE_LOG
 
 The arguments are I<log-level> and I<message>. The log level is small for
@@ -130,6 +273,11 @@ level is B<LOG_DEBUG>, the most important level is B<LOG_ERR>. In between there
 are (from least to most important): B<LOG_INFO>, B<LOG_NOTICE>, and
 B<LOG_WARNING>. I<message> is simply a string B<without> a newline at the end.
 
+=item TYPE_NOTIF
+
+The only argument passed is I<notification>. See above for the layout of this
+data type.
+
 =back
 
 =item B<plugin_unregister> (I<type>, I<plugin>)
@@ -144,11 +292,265 @@ is found (and the number of values matches the number of data-sources) then the
 type, data-set and value-list is passed to all write-callbacks that are
 registered with the daemon.
 
+=item B<plugin_flush> ([B<timeout> => I<timeout>,] [B<plugins> => I<...>])
+
+Flush one or more plugins. I<timeout> is passed on to the registered
+flush-callbacks. If omitted, C<-1> is used. If the I<plugins> argument has
+been specified, only named plugins will be flushed. The argument's value may
+either be a string or a reference to an array of strings.
+
+=item B<plugin_flush_one> (I<timeout>, I<plugin>)
+
+This is identical to using "plugin_flush (timeout =E<gt> I<timeout>, plugins
+=E<gt> I<plugin>".
+
+=item B<plugin_flush_all> (I<timeout>)
+
+This is identical to using "plugin_flush (timeout =E<gt> I<timeout>)".
+
+=item B<plugin_dispatch_notification> (I<notification>)
+
+Submits a I<notification> to the daemon which will then pass it to all
+notification-callbacks that are registered.
+
 =item B<plugin_log> (I<log-level>, I<message>)
 
 Submits a I<message> of level I<log-level> to collectd's logging mechanism.
 The message is passed to all log-callbacks that are registered with collectd.
 
+=item B<ERROR>, B<WARNING>, B<NOTICE>, B<INFO>, B<DEBUG> (I<message>)
+
+Wrappers around B<plugin_log>, using B<LOG_ERR>, B<LOG_WARNING>,
+B<LOG_NOTICE>, B<LOG_INFO> and B<LOG_DEBUG> respectively as I<log-level>.
+
+=back
+
+=head1 GLOBAL VARIABLES
+
+=over 4
+
+=item B<$hostname_g>
+
+As the name suggests this variable keeps the hostname of the system collectd
+is running on. The value might be influenced by the B<Hostname> or
+B<FQDNLookup> configuration options (see L<collectd.conf(5)> for details).
+
+=item B<$interval_g>
+
+This variable keeps the interval in seconds in which the read functions are
+queried (see the B<Interval> configuration option).
+
+=back
+
+Any changes to these variables will be globally visible in collectd.
+
+=head1 EXPORTS
+
+By default no symbols are exported. However, the following export tags are
+available (B<:all> will export all of them):
+
+=over 4
+
+=item B<:plugin>
+
+=over 4
+
+=item B<plugin_register> ()
+
+=item B<plugin_unregister> ()
+
+=item B<plugin_dispatch_values> ()
+
+=item B<plugin_flush> ()
+
+=item B<plugin_flush_one> ()
+
+=item B<plugin_flush_all> ()
+
+=item B<plugin_dispatch_notification> ()
+
+=item B<plugin_log> ()
+
+=back
+
+=item B<:types>
+
+=over 4
+
+=item B<TYPE_INIT>
+
+=item B<TYPE_READ>
+
+=item B<TYPE_WRITE>
+
+=item B<TYPE_FLUSH>
+
+=item B<TYPE_SHUTDOWN>
+
+=item B<TYPE_LOG>
+
+=back
+
+=item B<:ds_types>
+
+=over 4
+
+=item B<DS_TYPE_COUNTER>
+
+=item B<DS_TYPE_GAUGE>
+
+=back
+
+=item B<:log>
+
+=over 4
+
+=item B<ERROR> ()
+
+=item B<WARNING> ()
+
+=item B<NOTICE> ()
+
+=item B<INFO> ()
+
+=item B<DEBUG> ()
+
+=item B<LOG_ERR>
+
+=item B<LOG_WARNING>
+
+=item B<LOG_NOTICE>
+
+=item B<LOG_INFO>
+
+=item B<LOG_DEBUG>
+
+=back
+
+=item B<:notif>
+
+=over 4
+
+=item B<NOTIF_FAILURE>
+
+=item B<NOTIF_WARNING>
+
+=item B<NOTIF_OKAY>
+
+=back
+
+=item B<:globals>
+
+=over 4
+
+=item B<$hostname_g>
+
+=item B<$interval_g>
+
+=back
+
+=back
+
+=head1 EXAMPLES
+
+Any Perl plugin will start similar to:
+
+  package Collectd::Plugins::FooBar;
+
+  use strict;
+  use warnings;
+
+  use Collectd qw( :all );
+
+A very simple read function will look like:
+
+  sub foobar_read
+  {
+    my $vl = { plugin => 'foobar' };
+    $vl->{'values'} = [ rand(42) ];
+    plugin_dispatch_values ('gauge', $vl);
+    return 1;
+  }
+
+A very simple write function will look like:
+
+  sub foobar_write
+  {
+    my ($type, $ds, $vl) = @_;
+    for (my $i = 0; $i < scalar (@$ds); ++$i) {
+      print "$vl->{'plugin'} ($vl->{'type'}): $vl->{'values'}->[$i]\n";
+    }
+    return 1;
+  }
+
+To register those functions with collectd:
+
+  plugin_register (TYPE_READ, "foobar", "foobar_read");
+  plugin_register (TYPE_WRITE, "foobar", "foobar_write");
+
+See the section "DATA TYPES" above for a complete documentation of the data
+types used by the read and write functions.
+
+=head1 NOTES
+
+=over 4
+
+=item
+
+Please feel free to send in new plugins to collectd's mailinglist at
+E<lt>collectdE<nbsp>atE<nbsp>verplant.orgE<gt> for review and, possibly,
+inclusion in the main distribution. In the latter case, we will take care of
+keeping the plugin up to date and adapting it to new versions of collectd.
+
+Before submitting your plugin, please take a look at
+L<http://collectd.org/dev-info.shtml>.
+
+=back
+
+=head1 CAVEATS
+
+=over 4
+
+=item
+
+collectd is heavily multi-threaded. Each collectd thread accessing the perl
+plugin will be mapped to a Perl interpreter thread (see L<threads(3perl)>).
+Any such thread will be created and destroyed transparently and on-the-fly.
+
+Hence, any plugin has to be thread-safe if it provides several entry points
+from collectd (i.E<nbsp>e. if it registers more than one callback or if a
+registered callback may be called more than once in parallel). Please note
+that no data is shared between threads by default. You have to use the
+B<threads::shared> module to do so.
+
+=item
+
+Each function name registered with collectd has to be available before the
+first thread has been created (i.E<nbsp>e. basically at compile time). This
+basically means that hacks (yes, I really consider this to be a hack) like
+C<*foo = \&bar; plugin_register (TYPE_READ, "plugin", "foo");> most likely
+will not work. This is due to the fact that the symbol table is not shared
+across different threads.
+
+=item
+
+Each plugin is usually only loaded once and kept in memory for performance
+reasons. Therefore, END blocks are only executed once when collectd shuts
+down. You should not rely on END blocks anyway - use B<shutdown functions>
+instead.
+
+=back
+
+=head1 KNOWN BUGS
+
+=over 4
+
+=item
+
+Currently, it is not possible to flush a single Perl plugin only. You can
+either flush all Perl plugins or none at all and you have to use C<perl> as
+plugin name when doing so.
+
 =back
 
 =head1 SEE ALSO
@@ -156,12 +558,20 @@ The message is passed to all log-callbacks that are registered with collectd.
 L<collectd(1)>,
 L<collectd.conf(5)>,
 L<collectd-exec(5)>,
-L<perl(1)>
+L<types.db(5)>,
+L<perl(1)>,
+L<threads(3perl)>,
+L<threads::shared(3perl)>,
+L<perldebug(1)>
 
 =head1 AUTHOR
 
-The C<perl plugin> has been written by Sebastian Harl E<lt>shE<nbsp>atE<nbsp>tokkee.orgE<gt>.
+The C<perl plugin> has been written by Sebastian Harl
+E<lt>shE<nbsp>atE<nbsp>tokkee.orgE<gt>.
 
-This manpage has been written by Florian Forster E<lt>octoE<nbsp>atE<nbsp>verplant.orgE<gt>.
+This manpage has been written by Florian Forster
+E<lt>octoE<nbsp>atE<nbsp>verplant.orgE<gt> and Sebastian Harl
+E<lt>shE<nbsp>atE<nbsp>tokkee.orgE<gt>.
 
 =cut
+