munin aggregate graph problems

Question

Munin is driving me crazy. I'm trying to get an aggregate graph working. Here is my conf file:

[Mydomain;machine-1]
address xxx.xxx.xxx.xxx
use_node_name yes

[Mydomain;machine-2]
address xxx.xxx.xxx.xxx
use_node_name yes

[Mydomain;Aggregated]
update no
contacts n
stockg.graph_title example
stockg.graph_vlabel examplelabel
stockg.hits_load.draw LINE2
stockg.graph_args --base 1000
stockg.graph_category examplecat
stockg.hits_load.label example
stockg.hits_load.type DERIVE
stockg.hits_load.min 0
stockg.hits_load.sum machine-1:example.exampleline \
  machine-2:example.exampleline

the example plugin is below, which is running on 2 VMs - machine-1 and machine-2. (the third VM is munin master). Written in bash:

case $1 in
config)
cat << 'EOM'
graph_title test plugin
graph_vlabel amount of x
exampleline.label example line
EOM
exit 0;;
esac

echo -n "exampleline.value "
echo 5

The problems are:

1. I only get a single spike on the resulting graph, up to 10 then it immediately goes to 0. On subsequent runs there is no new data. Even if I change the plugin from 'echo 5' to 'echo 7' there is still no new data. It looks like munin master doesn't pick up changes on the nodes (yes I am running service munin-node restart after changes)

2. The graph doesnt show at all if I change from DERIVE to STACK

can someone help explain why munin isn't graphing correctly please? The individual graphs work, it's just the aggregate ones which are problematic.

Answer 1

This seems like expected behavior from a DERIVE data source. Since your plugin output is constant, munin sees one instance of 10 x/5 minutes the first time it runs and after that there's no change in the amount of x, so its derived value is 0.

You should set stockg.hits_load.type to GAUGE; that will just graph the absolute value.

I'll note that I've only ever used aggregation with GAUGE data. If your actual source data is COUNTER or DERIVE, I don't know how that interacts with munin's data aggregation.