SNMP lookup not working

[Elliott Balsley]

I'm trying to configure snmp-exporter with a PDU, using a lookup to label each outlet with its human-readable name (outletName) by referencing its outletIndex.  But when I try to do this, the outletName label is an empty string.  Is there something wrong with my generator config?  Example:

    walk:
      - 1.3.6.1.4.1.1418.6.5
    lookups:
      - source_indexes: [outletIndex]
        lookup: outletName

This is how the metrics look.

outletStatus{outletIndex="0",outletName=""} 1

Without any lookups, the outletName appears correct:

outletName{outletIndex="0",outletName="1-MacStudio"} 1

Below is how the raw SNMP data looks:

% snmptable -v2c -c netflixsnmp -m IBOOTPDU-MIB 10.37.155.163 1.3.6.1.4.1.1418.6.5
SNMP table: IBOOTPDU-MIB::outletTable

 outletIndex    outletName outletInitialState outletCycleTime outletControl outletStatus outletActualStatus
           1   1-MacStudio               last              10            on           on                 on
           2     2-Mezzo-1               last              10            on           on                 on
           3 3-UltraStudio               last              10            on           on                 on
           4       4-MP-60               last              10            on           on                 on
           5     5-Mezzo-2               last              10            on           on                 on
           6    6-Core110f               last              10            on           on                 on
           7      Outlet-7               last              10            on           on                 on
           8        8-Roku               last              10         cycle           on                 on

I'm not sure if this matters but I noticed the outletIndex values start at 1, while the OID table indexes start at 0.  Could that be the problem here?

I've attached the MIB.  I also opened a Github issue with more details in case this is a bug: https://github.com/prometheus/snmp_exporter/issues/1039

[Elliott Balsley]

Aha!  I found the problem by looking closer at the generated snmp.yml.  This PDU manufacturer OID is 1418.  I have another MIB installed from a different manufacturer 1718 which also has an OID called outletName.  So the generator config I shared before actually produces incorrect snmp.yml as below.  The solution I found is to be explicit in the lookup like this:

lookups:

- source_indexes: [outletIndex]

lookup: 1.3.6.1.4.1.1418.6.5.1.2

Is this expected behavior and is there a better way to handle it?

Incorrect snmp.yml:

- name: outletStatus

oid: 1.3.6.1.4.1.1418.6.5.1.6

type: gauge

help: ' - 1.3.6.1.4.1.1418.6.5.1.6'

indexes:

- labelname: outletIndex

type: gauge

lookups:

- labels:

- outletIndex

labelname: outletName

oid: 1.3.6.1.4.1.1718.3.2.3.1.3

type: DisplayString

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[Ben Kochie]

Have you updated your generator recently? We added a patch that tries to use OIDs closer to the original index first.

See: https://github.com/prometheus/snmp_exporter/pull/828

There's also now support for multiple files in the exporter, as well as different input filenames in the generator. You could do something like this:

MIBDIRS="mibs/base:mibs/vendorA" generator --generator-path="generator-vendorA.yml" --output-path="snmp-vendorA.yml"

MIBDIRS="mibs/base:mibs/vendorB" generator --generator-path="generator-vendorB.yml" --output-path="snmp-vendorB.yml"

snmp_exporer --config.file="snmp-*.yml"

Longer-term, I want to add the ability to specify MIBDIRS pre module in the generator. This way you can put the conflicting MIBs in different dirs and still have one config.

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[Elliott Balsley]

Nice, that sounds like it might fix it. I’m running the docker image prom/snmp-agent:main which was published 2 days ago. But I don’t know which commit that refers to.

I read the description of this new patch:

 first attempt to match the lookup node so that the OID matches that of the metric in all but the last branch.
In case no match is found, it reverts to the old behavior.

Would it be better to attempt this recursively, so if it fails to find the name in the last branch, then it looks one branch up, and so on? I’m curious, if it were implemented that way, would there ever be a need to specify multiple MIBDIRS?

[Ben Kochie]

Yea, the `main` Docker image has issues with being behind release, there's an open PR to fix it.