New beta hobbit - rrd disk cache and graph display
list Werner - Google
Hi, As always kudos Henrik for the excellent work. I didn't start do play with the new hobbit beta version, who good improvements about the disk I/O limitations on huge load systems. I have a specific question about what's hobbit behavior when disk cache for rrd is active, and i request the graph for a specific metric. Will i not see the last (around) 30 minutes of info on the graph? Or is there some kind "trap" activated when i request a specific graph, who'll request that the info for that host/service should be written to the RRD before the graph is generated? Regards Werner
list Sean R. Clark
i am running this version it appears (to me) that it writes that specific RRD you are looking at so there is no delay in the data [i am actually running 4.2.0 with only the 3 files changed in the beta version, which includes that hobbitgraph.cgi] -Sean
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From: Werner - Google [mailto:user-fc53c34471bb@xymon.invalid]
Sent: Monday, September 03, 2007 11:15 AM
To: user-ae9b8668bcde@xymon.invalid
Subject: [hobbit] New beta hobbit - rrd disk cache and graph display
Hi,
As always kudos Henrik for the excellent work.
I didn't start do play with the new hobbit beta version, who good
improvements about the disk I/O limitations on huge load systems. I have a
specific question about what's hobbit behavior when disk cache for rrd is
active, and i request the graph for a specific metric. Will i not see the
last (around) 30 minutes of info on the graph? Or is there some kind "trap"
activated when i request a specific graph, who'll request that the info for
that host/service should be written to the RRD before the graph is
generated?
Regards
Werner
list Henrik Størner
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In <user-ec2ff1dbb2cf@xymon.invalid> "Werner - Google" <user-fc53c34471bb@xymon.invalid> writes:
I didn't start do play with the new hobbit beta version, who good improvements about the disk I/O limitations on huge load systems. I have a specific question about what's hobbit behavior when disk cache for rrd is active, and i request the graph for a specific metric. Will i not see the last (around) 30 minutes of info on the graph? Or is there some kind "trap" activated when i request a specific graph, who'll request that the info for that host/service should be written to the RRD before the graph is generated?
The program that generates the graph will request a cache flush before doing the graph. There's no synchronization between the two, but since hobbitgraph.cgi and hobbitd_rrd are running on the same physical server, it should be Ok if hobbitgraph.cgi just waits "a while" - which I've randomly chosen to be 0.3 seconds. Also, the way the caching works doesn't simply delay all updates for 30 minutes (that would make the server extremely busy while flushing all of the cached data every 30 minutes, and then mostly idle for a long time), it actively tries to distribute the updates over the entire period. So the average amount of data cached when you request a graph will be 15 minutes. Regards, Henrik