rrdtool plugin: Updated the documentation in `collectd.conf(5)'

.. and the sample config file.

diff --git a/src/collectd.conf.in b/src/collectd.conf.in
index 90e20ba..c564ee2 100644 (file)
--- a/src/collectd.conf.in
+++ b/src/collectd.conf.in
@@ -10,9 +10,9 @@
 #Server ff18::efc0:4a42 25826
 #Server 239.192.74.66 25826
 
-#BaseDir   /opt/collectd/var/lib/collectd
-#PIDFile   /opt/collectd/var/run/collectd.pid
-#PluginDir /opt/collectd/lib/collectd
+#BaseDir   "/opt/collectd/var/lib/collectd"
+#PIDFile   "/opt/collectd/var/run/collectd.pid"
+#PluginDir "/opt/collectd/lib/collectd"
 
 @BUILD_MODULE_APACHE_TRUE@LoadPlugin apache
 @BUILD_MODULE_APCUPS_TRUE@LoadPlugin apcups
@@ -103,6 +103,8 @@
 
 #<Plugin rrdtool>
 #      CacheTimeout 120
+#      CacheFlush   900
+#      DataDir      "/opt/collectd/var/lib/collectd"
 #</Plugin>
 
 ## There are two different naming schemes for the sensors plugin, to preserver

diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index 5cedace..b25384c 100644 (file)
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -310,13 +310,26 @@ Sets the Time-To-Live of generated ICMP packets.
 
 =over 4
 
+=item B<CacheFlush> I<Seconds>
+
+When the C<rrdtool plugin> uses a cache (by setting B<CacheTimeout>, see below)
+it writes all values for a certain RRD-file if the oldest value is older than
+(or equal to) the number of seconds specified. If some RRD-file is not updated
+anymore for some reason (the computer was shut down, the network is broken,
+etc.) some values may still be in the cache. If B<CacheFlush> is set, then the
+entire cache is searched for entries older than B<CacheTimeout> seconds and
+written to disk every I<Seconds> seconds. Since this is kind of expensive and
+does nothing under normal circumstances, this value should not be too small.
+900 seconds might be a good value, though setting this to 7200 seconds doesn't
+normally do much harm either.
+
 =item B<CacheTimeout> I<Seconds>
 
-If this option is set to a value greater than zero, the C<rrdtool>-plugin will
-write values every I<Seconds> seconds to the RRD-files. Writing multiple values
-at once reduces IO-operations and thus lessens the load produced by updating
-the files. The tradeoff is that the graphs kind of "drag behind" and that more
-memory is used.
+If this option is set to a value greater than zero, the C<rrdtool plugin> will
+save values in a cache, as described above. Writing multiple values at once
+reduces IO-operations and thus lessens the load produced by updating the files.
+The tradeoff is that the graphs kind of "drag behind" and that more memory is
+used.
 
 =item B<DataDir> I<Directory>