Merge branch 'ff/aggregate'

[collectd.git] / src / collectd.conf.pod

diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index d7aba7bce08fa2461a3af3481af2d2a441db26be..f6f61c7e3da30285d516663ab9d901fbed2cb9ce 100644 (file)
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -193,12 +193,122 @@ C<Plugin>-Section. Which options exist depends on the plugin used. Some plugins
 require external configuration, too. The C<apache plugin>, for example,
 required C<mod_status> to be configured in the webserver you're going to
 collect data from. These plugins are listed below as well, even if they don't
-require any configuration within collectd's configfile.
+require any configuration within collectd's configuration file.
 
 A list of all plugins and a short summary for each plugin can be found in the
 F<README> file shipped with the sourcecode and hopefully binary packets as
 well.
 
+=head2 Plugin C<aggregation>
+
+The I<Aggregation plugin> makes it possible to aggregate several values into
+one using aggregation functions such as I<sum>, I<average>, I<min> and I<max>.
+This can be put to a wide variety of uses, e.g. average and total CPU
+statistics for your entire fleet.
+
+The grouping is powerful but, as with many powerful tools, may be a bit
+difficult to wrap your head around. The grouping will therefore be
+demonstrated using an example: The average and sum of the CPU usage across
+all CPUs of each host is to be calculated.
+
+To select all the affected values for our example, set C<Plugin cpu> and
+C<Type cpu>. The other values are left unspecified, meaning "all values". The
+I<Host>, I<Plugin>, I<PluginInstance>, I<Type> and I<TypeInstance> options
+work as if they were specified in the C<WHERE> clause of an C<SELECT> SQL
+statement.
+
+  Plugin "cpu"
+  Type "cpu"
+
+Although the I<Host>, I<PluginInstance> (CPU number, i.e. 0, 1, 2, ...)  and
+I<TypeInstance> (idle, user, system, ...) fields are left unspecified in the
+example, the intention is to have a new value for each host / type instance
+pair. This is achieved by "grouping" the values using the C<GroupBy> option.
+It can be specified multiple times to group by more than one field.
+
+  GroupBy "Host"
+  GroupBy "TypeInstance"
+
+We do neither specify nor group by I<plugin instance> (the CPU number), so all
+metrics that differ in the CPU number only will be aggregated. Each
+aggregation needs I<at least one> such field, otherwise no aggregation would
+take place.
+
+The full example configuration looks like this:
+
+ <Plugin "aggregation">
+   <Aggregation>
+     Plugin "cpu"
+     Type "cpu"
+     
+     GroupBy "Host"
+     GroupBy "TypeInstance"
+     
+     CalculateSum true
+     CalculateAverage true
+   </Aggregation>
+ </Plugin>
+
+There are a couple of limitations you should be aware of:
+
+=over 4
+
+=item
+
+The I<Type> cannot be left unspecified, because it is not reasonable to add
+apples to oranges. Also, the internal lookup structure won't work if you try
+to group by type.
+
+=item
+
+There must be at least one unspecified, ungrouped field. Otherwise nothing
+will be aggregated.
+
+=back
+
+As you can see in the example above, each aggregation has its own
+B<Aggregation> block. You can have multiple aggregation blocks and aggregation
+blocks may match the same values, i.e. one value list can update multiple
+aggregations. The following options are valid inside B<Aggregation> blocks:
+
+=over 4
+
+=item B<Host> I<Host>
+
+=item B<Plugin> I<Plugin>
+
+=item B<PluginInstance> I<PluginInstance>
+
+=item B<Type> I<Type>
+
+=item B<TypeInstance> I<TypeInstance>
+
+Selects the value lists to be added to this aggregation. B<Type> must be a
+valid data set name, see L<types.db(5)> for details.
+
+=item B<GroupBy> B<Host>|B<Plugin>|B<PluginInstance>|B<TypeInstance>
+
+Group valued by the specified field. The B<GroupBy> option may be repeated to
+group by multiple fields.
+
+=item B<CalculateNum> B<true>|B<false>
+
+=item B<CalculateSum> B<true>|B<false>
+
+=item B<CalculateAverage> B<true>|B<false>
+
+=item B<CalculateMinimum> B<true>|B<false>
+
+=item B<CalculateMaximum> B<true>|B<false>
+
+=item B<CalculateStddev> B<true>|B<false>
+
+Boolean options for enabling calculation of the number of value lists, their
+sum, average, minimum, maximum andE<nbsp>/ or standard deviation. All options
+are disabled by default.
+
+=back
+
 =head2 Plugin C<amqp>
 
 The I<AMQMP plugin> can be used to communicate with other instances of