When using 95th Percentiles, undefined index errors can be generated

[bellwood]

Describe the bug

Running Version 1.2.11

Graphs using 95th show a flatline at 0. This behaviour started on v1.2.8.

When I try to edit one of these graphs, I get the following logged:

2020/05/01 08:16:44 - CMDPHP PHP ERROR NOTICE Backtrace: (/graphs.php[116]:graph_edit(), /graphs.php[1611]:rrdtool_function_graph(), /lib/rrd.php[1586]:variable_nth_percentile(), /lib/graph_variables.php[451]:nth_percentile(), /lib/graph_variables.php[36]:CactiErrorHandler())
--
2020/05/01 081:16:44 - ERROR PHP NOTICE: Undefined index: peak in file: /usr/local/share/cacti/lib/graph_variables.php on line: 36

This makes no sense as the nth_percentile function has a default argument $peak = false so how can it not be defined?

[bellwood]

Debug:

/usr/local/bin/rrdtool graph - \
--imgformat=PNG \
--start='-86400' \
--end='-300' \
--pango-markup  \
--title='REDACTED' \
--vertical-label='bits per second' \
--slope-mode \
--base=1000 \
--height=200 \
--width=700 \
--rigid \
--alt-autoscale-max \
--lower-limit='0' \
COMMENT:"From 2020/04/30 16\:11\:23 To 2020/05/01 16\:06\:23\c" \
COMMENT:"  \n" \
--color BACK#F3F3F3 \
--color CANVAS#FDFDFD \
--color SHADEA#CBCBCB \
--color SHADEB#999999 \
--color FONT#000000 \
--color AXIS#2C4D43 \
--color ARROW#2C4D43 \
--color FRAME#2C4D43 \
--border 1 --font TITLE:11:'Arial' \
--font AXIS:8:'Arial' \
--font LEGEND:8:'Courier' \
--font UNIT:8:'Arial' \
--font WATERMARK:6:'Arial' \
--slope-mode \
DEF:a='/var/db/cacti/rra/72/2677.rrd':'traffic_in':AVERAGE \
DEF:b='/var/db/cacti/rra/72/2677.rrd':'traffic_out':AVERAGE \
CDEF:cdefa='a,8,*' \
CDEF:cdeff='b,8,*' \
LINE1:cdefa#00CF00FF:  \
AREA:cdefa#00CF007F:'Inbound '  \
GPRINT:cdefa:LAST:'Current\:%8.2lf %s'  \
GPRINT:cdefa:AVERAGE:'Average\:%8.2lf %s'  \
GPRINT:cdefa:MAX:'Maximum\:%8.2lf %s\n'  \
LINE1:cdeff#002A97FF:  \
AREA:cdeff#002A977F:'Outbound'  \
GPRINT:cdeff:LAST:'Current\:%8.2lf %s'  \
GPRINT:cdeff:AVERAGE:'Average\:%8.2lf %s'  \
GPRINT:cdeff:MAX:'Maximum\:%8.2lf %s\n'  \
COMMENT:' \n'  \
HRULE:0#FF0000FF:'95th Percentile' \
COMMENT:'(0 mbit in+out)' 
RRDtool Command lengths = 1331 charaters.
RRDtool Says:
OK

[bellwood]

Template bits RE: 95th:

HRULE: |95:bits:0:max:2|
COMMENT: (|95:bits:6:max:2| mbit in+out)

[netniV]

Yeah I believe the problem here lies with the checking of the return type from nth_percentile() which in turn doesn't check the return from rrdtool_function_stats()

Ultimately, these get used by variable_nth_percentile() and I'm not confident how far beyond a knock on effect would have in correcting that, so it won't make this weekends release.

[bellwood]

@netniV thanks, this one has raised a few eyebrows.

[frontierliu]

This bug is about lack of check in nth_percentile().
Rrdtool_functions_stats() only return 2 arrays: $stats['peak'] and $stats['avg']，
corresponding to datasource CF max and avg. when 95th template use keywords include 'max', 'peak', it would prefer to $stats['peak'], the other keywords would prefer to $stats['avg']. When user defined 95th like '|95:bits:0:max:2|' and he only defined datasource CF = avg ( lack of CF=max ), the bug "undefined index 'peak'..."is appeared.

How to improve check and resolved:
In graph_variables.php, line 36:

diff --git a/usr/local/github/cacti/lib/graph_variables.php b/usr/local/cacti/lib/graph_variables.php
index fa34f6f..39cb440 100644
--- a/usr/local/github/cacti/lib/graph_variables.php
+++ b/usr/local/cacti/lib/graph_variables.php
@@ -33,9 +33,21 @@ function nth_percentile($local_data_ids, $start_seconds, $end_seconds, $percenti
        $stats = json_decode(rrdtool_function_stats($local_data_ids, $start_seconds, $end_seconds, $percentile, $resolution, $peak), true);
 
        if ($peak) {
-               return $stats['peak'];
+               if (array_key_exists('peak', $stats)) {
+                       return $stats['peak'];
+               } else if (array_key_exists('avg', $stats)) {
+                       return $stats['avg'];
+               } else {
+                       return $stats;
+               }
        } else {
-               return $stats['avg'];
+               if (array_key_exists('avg', $stats)) {
+                       return $stats['avg'];
+               } else if (array_key_exists('peak', $stats)) {
+                       return $stats['peak'];
+               } else {
+                       return $stats;
+               }
        }
 }

[netniV]

That does seem reasonable, thanks @frontierliu. Can you do that as a PR with a CHANGELOG entry (preferably with an english readable title than this issue's one - I can update the issue later)

[bellwood]

This is still an issue.

We updated to 1.2.12, same issue.

Error is basically the same, just a different line now:

2020/05/08 23:43:51 - CMDPHP PHP ERROR NOTICE Backtrace: (/graph.php[541]:rrdtool_function_graph(), /lib/rrd.php[1586]:variable_nth_percentile(), /lib/graph_variables.php[454]:nth_percentile(), /lib/graph_variables.php[38]:CactiErrorHandler())
--
2020/05/08 23:43:51 - ERROR PHP NOTICE: Undefined index: peak in file: /usr/local/share/cacti/lib/graph_variables.php on line: 38

Graph Debug:

RRDtool Command:
/usr/local/bin/rrdtool graph - \
--imgformat=PNG \
--start='1588909620' \
--end='1588981373' \
--pango-markup  \
--title='REDACTED' \
--vertical-label='bits per second' \
--slope-mode \
--base=1000 \
--height=200 \
--width=700 \
--rigid \
--alt-autoscale-max \
--lower-limit='0' \
COMMENT:"From 2020/05/08 03\:47\:00 To 2020/05/08 23\:42\:53\c" \
COMMENT:"  \n" \
--color BACK#F3F3F3 \
--color CANVAS#FDFDFD \
--color SHADEA#CBCBCB \
--color SHADEB#999999 \
--color FONT#000000 \
--color AXIS#2C4D43 \
--color ARROW#2C4D43 \
--color FRAME#2C4D43 \
--border 1 --font TITLE:11:'Arial' \
--font AXIS:8:'Arial' \
--font LEGEND:8:'Courier' \
--font UNIT:8:'Arial' \
--font WATERMARK:6:'Arial' \
--slope-mode \
DEF:a='/var/db/cacti/rra/72/2677.rrd':'traffic_in':AVERAGE \
DEF:b='/var/db/cacti/rra/72/2677.rrd':'traffic_out':AVERAGE \
CDEF:cdefa='a,8,*' \
CDEF:cdeff='b,8,*' \
LINE1:cdefa#00CF00FF:  \
AREA:cdefa#00CF007F:'Inbound '  \
GPRINT:cdefa:LAST:'Current\:%8.2lf %s'  \
GPRINT:cdefa:AVERAGE:'Average\:%8.2lf %s'  \
GPRINT:cdefa:MAX:'Maximum\:%8.2lf %s\n'  \
LINE1:cdeff#002A97FF:  \
AREA:cdeff#002A977F:'Outbound'  \
GPRINT:cdeff:LAST:'Current\:%8.2lf %s'  \
GPRINT:cdeff:AVERAGE:'Average\:%8.2lf %s'  \
GPRINT:cdeff:MAX:'Maximum\:%8.2lf %s\n'  \
COMMENT:' \n'  \
HRULE:0#FF0000FF:'95th Percentile' \
COMMENT:'(0 mbit in+out)' 
RRDtool Command lengths = 1341 charaters.
RRDtool Says:
OK