No negative values can be displayed in graphs

[Peter Gervai]

It seems NAV reads SFP tx/rx levels but cannot handle negative results like -17.1 dBm. Instead it logs "no value".

[Morten Brekkevold (mbrekkevold)]

I'm assuming the tx/rx values are collected as part of the sensors collection (at least on Cisco, TX/RX of SFP's are usually reported as sensors whose values can be read).

It might help if you set 'nav.ipdevpoll.plugins.statsensors = DEBUG' in `logging.conf`. This should debug log the raw values NAV reads from the device. There might be something wrong that happens when converting the number to the given precision of the sensor.

[Peter Gervai (grin)]

 [DEBUG plugins.statsensors.statsensors] [1minstats c6506aggregator.head.sex] got data from sensors:
.....
('nav.devices.c6506aggregator_head_sex.sensors.Gi2_2_Transmit_Power_Sensor', (1429262887.206605, -2.0)), ('nav.devices.c6506aggregator_head_sex.sensors.Gi5_1_Receive_Power_Sensor', (1429262887.206605, -5.5))

Okay, I have found the problem:

...&yMin=0&...

You call graphite with this which screws up graphs with negative values. I guess you intended to have graphs with the same scale? :) There are a few graphs which may contain negative values, most notably anything which works with Tx or Rx power in dBmV or dB.

I checked a few MIBs and they're pretty inconlusive regarding data ranges. Often SYNTAX contains range like:
     SYNTAX Integer32 (0..1536)
     SYNTAX Integer32 (0..2147483647)
and it seems that it's not shown where the values may conver all the Int32 range, including negative values.

(Tehnically CISCO-ENTITY-SENSOR-MIB says that these sensor values are of type SensorValue which has the range -1000000000 - 1000000000, but I guess this syntax varies from mib to mib.)

[Morten Brekkevold (mbrekkevold)]

Aha, you are quite correct. NAV produces a default value of yMin=0 for all graph types - this is indeed a stupid bug.

[Morten Brekkevold (mbrekkevold)]

fix here: https://nav.uninett.no/hg/stable/rev/ff169d3c6cac