Difference between revisions of "Plugin:RRDCacheD"

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(Remove incorrect note about rrdtool / rrdcached incompatibility.)
(Relicensed to MIT license.)
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   | Status={{supported}}
   | Status={{supported}}
   | FirstVersion={{Version|4.6}}
   | FirstVersion={{Version|4.6}}
   | Copyright=''2008'' Florian octo Forster
   | Copyright=''2008–2013'' [[User:Octo|Florian Forster]]
   | License={{GPLv2}}
   | License={{MIT License}}
   | Manpage={{Manpage|collectd.conf|5|plugin_rrdcached}}
   | Manpage={{Manpage|collectd.conf|5|plugin_rrdcached}}

Latest revision as of 09:51, 21 May 2015

RRDCacheD plugin
Type: write
Callbacks: config, init, read, shutdown, write
Status: supported
First version: 4.6
Copyright: 2008–2013 Florian Forster
License: MIT license
Manpage: collectd.conf(5)
List of Plugins

The RRDCacheD plugin connects to the “RRD caching daemon”, rrdcached and submits updates for RRD files to that daemon. rrdcached is based on the RRDtool plugin of collectd and basically uses the same principles that are described in “Inside the RRDtool plugin”.

Having the cache in a separate process is some more work to set up, but has nice benefits, especially for big setups: You can restart collectd without flushing the cache, have the cache on a remote server and, of course, applications other than collectd can make use of it.

rrdcached has been included in the RRDtool distribution since version 1.4.


<Plugin "rrdcached">
  DaemonAddress "unix:/var/run/rrdcached.sock"
  DataDir "/var/lib/collectd/rrd"
  CreateFiles true

Example graphs

Rrdcached-write updates.png
Number of write operations per second.

RRDCacheD-operations-write data sets.png
Values written to disk per second. Since many values are written in one write operation, the number of write operations per second is much lower. As you can see if you compare this graph with the one above, there are in average 490 data sets in one write operation.

Rrdcached-receive update.png
Number of update commands received per second.

Rrdcached-journal bytes.png
Bytes per second written to the journal.

Rrdcached-queue length.png
Length of the update queue.

Rrdcached-tree nodes.png
Number of nodes (RRD files) in the binary search tree of the caching daemon.

Rrdcached-tree depth.png
Depth of the binary search tree used by the daemon. This is basically the number of comparisons needed to find any file in the tree.

See also


  • librrd (≧ 1.4. Version 1.3 is not recent enough!)