Hi Everyone,
As you know I've been hard at work creating a profiler for nagios that is s=
imple, flexible, extensible, fast and above all accurate.
My initial design was to create a collection of global timers gt_* and glob=
al odometers go_* variables that could then be written out to status.dat on=
e by one.
This worked ok but became quickly unwieldy for obvious reasons.
My next design was a linked list of objects containing the timer and the co=
unter, as well as name or event type, this made extensibility a snap, but w=
ould have made a significant impact on speed since we would have to walk th=
e list at best, and at worst do a strcmp on every single object every time =
we wanted to update a stat. So this idea was discarded for the time being.
Finally I had a better idea. Each event type is an integer and even though=
they aren't necessarily close together they would still be appropriate for=
an array index even if it's a sparse one.
So this is the new profiler design.
We have an object containing
elapsed time, counter, enabled
We have an array of these objects indexed by event type
profiler[event].counter++;
Then when we write it out to status.dat we have a very simple loop that loo=
ks to see if the event type is enabled for profiling and outputs it if it i=
s.
The output looks like
PROFILE_COUNTER_EVENT_SERVICE_CHECK=3D100
Nagiostats then looks for the word PROFILE, and then for COUNTER or ELAPSED=
, then adds that to a linked list ala my second design, and outputs via mrt=
g or the normal nagiostats output.
The other major difference is what we are using to calculate time.
In the original design we just used time(), but later we decided we needed =
more resolution so we went to clock(), finally it was discovered that using=
clock would introduce a bug every 72 minutes and so now we just use gettim=
eofday
In the next version I may include clock() time as well but I thought that t=
his would be sufficient for our needs.
Let me know what you think and I'll try to get a patch out ASAP.
Sincerely,
Steve
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