[rrd-users] Re: Inconsistencies between graph and fetch

[Tobias Oetiker]

Yesterday Philip Molter wrote:

 |
 |
 | : Today Philip Molter wrote:
 | :
 | :  |
 | :  | I'm using 1.0.28 on a Solaris 8 x86 box with the Perl hooks.
 | :
 | : make sure you are using 1.0.33 ... (hint hint)
 |
 | Ugh, I upgraded everything to 1.0.33 and now graphing is one off
 | in the other direction.

would you mind providing a little script which

* creates the rrd
* updates it with data
* fetches the data
* produces the graph

this might help to debug or explain

tobi
 |
 | For example, with the same setup, I get these results from RRD fetch:
 |
 |   Time      test1      test2
 |   ---------------------------
 |   $time + 5   5         NaN
 |   $time + 10  3         2
 |   $time + 15  4         4
 |
 | But when I do averages using graph for the exact same start and
 | end times ($time + 5 through $time + 15), I get averages of test1:3.5
 | and test2:3.  If I increase the period by doing (-s $time + 5 -
 | 1), then I get the correct values back using rrdgraph.
 |
 | Again, that seems like a pretty big inconsistency.  I would expect
 | my 'graphed' values to be using the same data that my fetch query
 | returns.  Apparently, now, graphing is inclusive of the ending
 | time, but exclusive of the start time, while fetching is still
 | inclusive of both.
 |
 | I've included my previous message below for refernece
 | Philip
 |
 | ----- Previous Message -----
 |
 | : I've setup a very basic file for testing.  Two fields, 5 second
 | : intervals, starting at time $time ($time is adjusted to be on a 5
 | : second boundary).
 | :
 | :   Field test1 is a GAUGE
 | :   Field test2 is a COUNTER
 | :
 | : At these times, I put in these values:
 | :
 | :   Time       test1      test2
 | :   ----------------------------
 | :   $time + 5    5          8
 | :   $time + 10   3          18
 | :   $time + 15   4          38
 | :
 | : When I do a fetch for the time period starting at $time + 5 and
 | : ending at $time + 15, I get these three rows:
 | :
 | :   Time       test1      test2
 | :   ----------------------------
 | :   $time + 5    5         NaN
 | :   $time + 10   3         2
 | :   $time + 15   4         4
 | :
 | : Thus, using that data, between the times of $time + 5 and $time +
 | : 15, I get an average value of 4 for test1 and 3 for test2.
 | :
 | : However, if I do a graph using the following values:
 | :
 | :   -
 | :   -s $time + 5
 | :   -e $time + 15
 | :   DEF:test1=file.rrd:test1:AVERAGE
 | :   DEF:test2=file.rrd:test2:AVERAGE
 | :   PRINT:test1:AVERAGE:%lf
 | :   PRINT:test2:AVERAGE:%lf
 | :
 | : I get back averages of 4 for test1 and 2 for test2.  It's like it's
 | : ignoring the $time + 15 entry for calculating the average value.
 | : If I increase the period by using (-e $time + 16), then I get the
 | : correct values.
 |
 | * Philip Molter
 | * DataFoundry.net
 | * http://www.datafoundry.net/
 | * philip at datafoundry.net
 |
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