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

Steve Shipway s.shipway at auckland.ac.nz
Thu Feb 3 00:36:02 CET 2011

> I think this should be cached in mrtg/routers2 ... since rrdtool
> info should really return 'the real thing' ... so if there was
> support for this in rrdcached then the option would have to be for
> --caching

That would be OK if MRTG was running in daemon mode (or Routers2 in mod_perl mode), but for people not using daemon mode, there would be no way for the info to be cached.  I'm making the assumption that the info function is usually called to obtain structure info, not current-value info, and then trying to squeeze some more performance out.  It's also worth noting that, although for cached info the values would be out of date, this is also the case (to a lesser extent) for normal info since many update values may be stored in the pending queue.

How about making the default behaviour of rrdcached to NOT cache info queries, but make a command-line option to enable this and set and info query cache timeout -- eg, '-I 600' to cache info-queries for up to 10mins?  Then people could only enable it when they were happy with the loss of reliability to the current-value data (which would already be suspect if running rrdcached in any case)


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
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Email: s.shipway at auckland.ac.nz
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