[rrd-developers] rrdtool 1.1 patch: src/rrd_fetch.c (RRA selection)

[Stanislav Sinyagin]

Hi all, 

see the patch and the resulting src/rrd_fetch.c attached. 
The problem appeared in the first 5 minutes of each half-hour 
interval, e.g. between 12:00 and 12:05, between 12:30 and 12:35 etc.

I tested this patch and didn't find any problems so far. 

Regards, 
Stan  



--- Stanislav Sinyagin <ssinyagin at yahoo.com> wrote:
> 
> Hi Tobi and all, 
> 
> I found the piece of code that does wrong, but I need your 
> help in fixing that. 
> 
> --- Stanislav Sinyagin <ssinyagin at yahoo.com> wrote:
> > Sometimes LINE2 is drawn with a bigger step than it's 
> > defined in RRD, though the rrd_graph arguments are 
> > the same. 
> > 
> > See these examples: 
> > 
> > Correct graph (except that TICK doesn't work):
> >    http://ipv6.multikabel.net/render-correct-1.bmp
> > 
> > Weird graph:
> >    http://ipv6.multikabel.net/render-fault-1.bmp
> 
> Thus, the RRD is created with the following RRAs, in the following 
> sequence:
>       RRA:AVERAGE:0:1:4032
>       RRA:AVERAGE:0:6:2016
>       RRA:MAX:0:6:2016
>       RRA:AVERAGE:0:288:732
>       RRA:MAX:0:288:732
> 
> Then, with DEBUG enabled in src/rrd_fetch.c, after few thousand of 
> looped rrdtool graph runs, I got the following debug output:
> 
> Entered rrd_fetch_fn() searching for the best match
> Looking for: start 1042459233 end 1042545633 step   172 rows  502
> Considering: start  979257600 end 1042502400 step 86400 best partial so far
> Considering: start 1038916800 end 1042545600 step  1800 best partial so far
> Considering: start 1041336000 end 1042545600 step   300 partial match, not best
> We found:    start 1042459200 end 1042547400 step  1800 rows  49
> 
> This means that in the loop at line 208 of src/rrd_fetch.c, 
> the condition "if (first_part || best_match < tmp_match)" at line 250 
> was false for the row with step 300. 
> 
> I think that changing the condition to 
>   "if (first_part || best_match <= tmp_match)"
> would help in my case. But that works only if the RRAs are sorted by 
> the step size. This is where I stuck: are the entries in this loop 
> sorted or not?
> 
> With regards, 
> 
> Stan.
> 
> 
> 
> 
> 
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-- Attached file removed by Ecartis and put at URL below --
-- Type: text/plain
-- Desc: rrdfetch.stsiny.patch
-- Size: 1k (1259 bytes)
-- URL : http://www.ee.ethz.ch/~slist/pantomime/rrdfetch.stsiny.patch


-- Attached file removed by Ecartis and put at URL below --
-- Type: text/plain
-- Desc: rrd_fetch.c
-- Size: 12k (12737 bytes)
-- URL : http://www.ee.ethz.ch/~slist/pantomime/rrd_fetch.c


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