+=head1 THRESHOLD CONFIGURATION
+
+Starting with version C<4.3.0> collectd has support for B<monitoring>. By that
+we mean that the values are not only stored or sent somewhere, but that they
+are judged and, if a problem is recognized, acted upon. The only action
+collectd takes itself is to generate and dispatch a "notification". Plugins can
+register to receive notifications and perform appropriate further actions.
+
+Since systems and what you expect them to do differ a lot, you can configure
+B<thresholds> for your values freely. This gives you a lot of flexibility but
+also a lot of responsibility.
+
+Every time a value is out of range a notification is dispatched. This means
+that the idle percentage of your CPU needs to be less then the configured
+threshold only once for a notification to be generated. There's no such thing
+as a moving average or similar - at least not now.
+
+Also, all values that match a threshold are considered to be relevant or
+"interesting". As a consequence collectd will issue a notification if they are
+not received for twice the last timeout of the values. If, for example, some
+hosts sends it's CPU statistics to the server every 60 seconds, a notification
+will be dispatched after about 120 seconds. It may take a little longer because
+the timeout is checked only once each B<Interval> on the server.
+
+Here is a configuration example to get you started. Read below for more
+information.
+
+ <Threshold>
+ <Type "foo">
+ WarningMin 0.00
+ WarningMax 1000.00
+ FailureMin 0.00
+ FailureMax 1200.00
+ Invert false
+ Instance "bar"
+ </Type>
+
+ <Plugin "interface">
+ Instance "eth0"
+ <Type "if_octets">
+ FailureMax 10000000
+ </Type>
+ </Plugin>
+
+ <Host "hostname">
+ <Type "cpu">
+ Instance "idle"
+ FailureMin 10
+ </Type>
+
+ <Plugin "memory">
+ <Type "memory">
+ Instance "cached"
+ WarningMin 100000000
+ </Type>
+ </Plugin>
+ </Host>
+ </Threshold>
+
+There are basically two types of configuration statements: The C<Host>,
+C<Plugin>, and C<Type> blocks select the value for which a threshold should be
+configured. The C<Plugin> and C<Type> blocks may be specified further using the
+C<Instance> option. You can combine the block by nesting the blocks, though
+they must be nested in the above order, i.E<nbsp>e. C<Host> may contain either
+C<Plugin> and C<Type> blocks, C<Plugin> may only contain C<Type> blocks and
+C<Type> may not contain other blocks. If multiple blocks apply to the same
+value the most specific block is used.
+
+The other statements specify the threshold to configure. They B<must> be
+included in a C<Type> block. Currently the following statements are recognized:
+
+=over 4
+
+=item B<FailureMax> I<Value>
+
+=item B<WarningMax> I<Value>
+
+Sets the upper bound of acceptable values. If unset defaults to positive
+infinity. If a value is greater than B<FailureMax> a B<FAILURE> notification
+will be created. If the value is greater than B<WarningMax> but less than (or
+equal to) B<FailureMax> a B<WARNING> notification will be created.
+
+=item B<FailureMin> I<Value>
+
+=item B<WarningMin> I<Value>
+
+Sets the lower bound of acceptable values. If unset defaults to negative
+infinity. If a value is less than B<FailureMin> a B<FAILURE> notification will
+be created. If the value is less than B<WarningMin> but greater than (or equal
+to) B<FailureMin> a B<WARNING> notification will be created.
+
+=item B<Invert> B<true>|B<false>
+
+If set to B<true> the range of acceptable values is inverted, i.E<nbsp>e.
+values between B<FailureMin> and B<FailureMax> (B<WarningMin> and
+B<WarningMax>) are not okay. Defaults to B<false>.
+
+=item B<Persist> B<true>|B<false>
+
+Sets how often notifications are generated. If set to B<true> one notification
+will be generated for each value that is out of the acceptable range. If set to
+B<false> (the default) then a notification is only generated if a value is out
+of range but the previous value was okay.
+
+This applies to missing values, too: If set to B<true> a notification about a
+missing value is generated once every B<Interval> seconds. If set to B<false>
+only one such notification is generated until the value appears again.
+
+=back
+