Has anyone tried using this yet?  The way to do it seems to be to set the 
environment variable RRDCACHED_ADDRESS to the same value as the -l parameter 
you used to start rrdcached, before running MRTG.

I've been testing this as part of my performance testing, and it seems a little 
immature.  The cached seems not to support such functions as tune, create, and 
info; only supporting update.

When rrdcached is running on a unix socket, MRTG seems to work and all is fine 
- I suspect the tune, create and info are done via the normal channels.  If you 
use a TCP address, though, you get lots of errors about 'dummy'.  I think this 
is the RRD functions choking because they cannot stat the RRD file, or create 
it.

There is also an issue that rrdcached rejects absolute paths for RRD files when 
submitted via TCP which seems to be in conflict with the way MRTG works.

Possibly MRTG should be patched to detect rrdcached mode, and in this case skip 
the various checks like verifying the MaxBytes (and tuning), checking for .log 
files, and so on.  You'd still need to have the rrd files pre-created unless 
rrdcached can support this in the next version, though.

If rrdcached can support create (as well as update) via TCP sockets then it 
will open up the possibility to have one server running rrdcached and the web 
frontend, and then a cluster of others running MRTG processes feeding back to 
the rrdcached, allowing a huge expansion...

I'm going to have a bit more of a play with this, but I'd be interested in 
hearing anyone else's experience with this.

Steve

________________________________
Steve Shipway
ITS Unix Services Design Lead
University of Auckland
Floor 2, 58 Symonds Street
09 3737599 ext 86487
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