[rrd-developers] rrdcached: info command: cacheable?

Steve Shipway s.shipway at auckland.ac.nz
Wed Feb 2 23:50:23 CET 2011

I'm coding up a quick change to rrd_daemon.c to make it cache the results of rrd_info calls for a predetermined period.  This means that any calls to rrdc_info (IE, rrdtool info over rrdcached) would be cached, speeding up retrieval at the cost of items such as 'last_update' and '*.value', '*.cur_row' etc being out of date.  Probably there would need to be an option to info to allow bypassing of the cache?

The motivation for this is that MRTG makes a substantial number of these calls (as does Routers2 and others) but are only interested in the structure of the RRD, not the current values.  By caching it would speed up access and minimise disk IO.

Thoughts, anyone?  I have yet to see how much actual difference it would make...


Steve Shipway
ITS Unix Services Design Lead
University of Auckland, New Zealand
Floor 1, 58 Symonds Street, Auckland
Phone: +64 (0)9 3737599 ext 86487
DDI: +64 (0)9 924 6487
Mobile: +64 (0)21 753 189
Email: s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz>
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