No negative SNMP values are stored in the rrd-file:

[Alpenjunge]

Hello
Since English is not my language, I use DeepL to translate, excuse me...

I've been trying to fix a problem for weeks and I'm stuck:
I want to monitor positive and negative outside temperatures. The values are retrieved via SNMP.
Problem: No negative SNMP values are stored in the rrd-file:
SNMP-Value:

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snmpget -v2c -c public 192.168.92.100 iso.3.6.1.4.1.2021.2000.4.4.1.2.5.116.101.109.112.51.1
iso.3.6.1.4.1.2021.2000.4.4.1.2.5.116.101.109.112.51.1 = STRING: "-10.22"

rrrd-File, filled via snmp not works correct:

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rrdtool info server_sonne_snmp_oid_130.rrd 
filename = "server_sonne_snmp_oid_130.rrd"
rrd_version = "0003"
step = 60
last_update = 1543848236
header_size = 3704
ds[snmp_oid].index = 0
ds[snmp_oid].type = "GAUGE"
ds[snmp_oid].minimal_heartbeat = 600
ds[snmp_oid].min = -2.0000000000e+01
ds[snmp_oid].max = 6.0000000000e+01
ds[snmp_oid].last_ds = "10.22"
ds[snmp_oid].value = 5.7232000000e+02
ds[snmp_oid].unknown_sec = 0

rrd-File, filled via rrdtools update works fine:

Code: Select all

rrdtool update server_sonne_snmp_oid_130.rrd N:-10.22
info server_sonne_snmp_oid_130.rrd 

filename = "server_sonne_snmp_oid_130.rrd"
rrd_version = "0003"
step = 60
last_update = 1543848563
header_size = 3704
ds[snmp_oid].index = 0
ds[snmp_oid].type = "GAUGE"
ds[snmp_oid].minimal_heartbeat = 600
ds[snmp_oid].min = -2.0000000000e+01
ds[snmp_oid].max = 6.0000000000e+01
ds[snmp_oid].last_ds = "-10.22"
ds[snmp_oid].value = -2.4172703744e+02
ds[snmp_oid].unknown_sec = 0

Where do I make the mistake?

---
Cacti V 1.2.0 Beta 2
RRDtool V1.0.0
NET-SNMP V 5.7.3

[Alpenjunge]

Unfortunately I did not receive a solution. But I have an idea for a workaround:
The values (temperature) provided by the script are increased by 100. Via CDEF 100 are subtracted again before the output. Only positive values are transferred via SNMP, now also negative values are displayed...

[jozhik]

I have the same problem

by snmp I get a negative value

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snmpget -v1 -c klotik_ro 10.215.130.21 .1.3.6.1.4.1.2021.2000.10.4.1.2.5.116.101.109.112.48.1
UCD-SNMP-MIB::ucdavis.2000.10.4.1.2.5.116.101.109.112.48.1 = STRING: "-22.25"

cacti writes a positive value to the rrd file

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rrdtool info /var/db/cacti/rra/local_linux_machine_term_8.rrd | grep term
filename = "/var/db/cacti/rra/local_linux_machine_term_8.rrd"
ds[term].index = 0
ds[term].type = "GAUGE"
ds[term].minimal_heartbeat = 600
ds[term].min = -4,0000000000e+01
ds[term].max = 1,0000000000e+02
ds[term].last_ds = "22.25"
ds[term].value = 0,0000000000e+00
ds[term].unknown_sec = 0

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uname -a
FreeBSD jail_2 11.2-RELEASE FreeBSD 11.2-RELEASE #0 r335510: Fri Jun 22 04:32:14 UTC 2018     root@releng2.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64
pkg info | grep cacti
cacti-1.1.38                   Web-driven graphing interface for RRDTool
pkg info | grep rrd
rrdtool-1.7.0_2                Round Robin Database Tools
pkg info | grep net-snmp
net-snmp-5.7.3_19              Extendable SNMP implementation

What needs to be changed to work properly cacti?

[jozhik]

The solution proposed by Alpenjunge is original. But I would like to make the cacti work properly

[Osiris]

Looks like this was reported as a bug here and resolved: https://github.com/Cacti/cacti/issues/2217