Extracting multiple metrics from SNMP string

[Elliott Balsley]

I have an SNMP device that returns a value like this:

DOLBY-CP850-MIB::cp850MeterLevels.0 = STRING: "00 00 00 00 00 00 00 00 00 00"

This string represents the volume level of 10 separate audio channels, so I would like to break it apart and record it as 10 metrics.  I previously had this working in Telegraf so the result looked like this:

snmp_dolby_cp_meter_level_dbfs{channel="L"} 0
snmp_dolby_cp_meter_level_dbfs{channel="R"} 0
snmp_dolby_cp_meter_level_dbfs{channel="C"} 0
snmp_dolby_cp_meter_level_dbfs{channel="LFE"} 0
snmp_dolby_cp_meter_level_dbfs{channel="Lss"} 0
snmp_dolby_cp_meter_level_dbfs{channel="Rss"} 0
snmp_dolby_cp_meter_level_dbfs{channel="Lrs"} 0
snmp_dolby_cp_meter_level_dbfs{channel="Rrs"} 0
snmp_dolby_cp_meter_level_dbfs{channel="Lts"} 0
snmp_dolby_cp_meter_level_dbfs{channel="Rts"} 0

Is this possible to do with snmp-exporter?  I couldn't find any way to add the channel label.  The best I could think of is this regex_extract in the exporter, but this isn't really what I want because it adds the channel identifier to the metric name.

      cp850MeterLevels:
        type: DisplayString
        regex_extracts:
          '_L':
          - regex: '(..) .. .. .. .. .. .. .. .. ..'
            value: $1
          '_R':
          - regex: '.. (..) .. .. .. .. .. .. .. ..'
            value: $1
          '_C':
          - regex: '.. .. (..) .. .. .. .. .. .. ..'
            value: $1
          '_LFE':
          - regex: '.. .. .. (..) .. .. .. .. .. ..'
            value: $1
          '_Lss':
          - regex: '.. .. .. .. (..) .. .. .. .. ..'
            value: $1
          '_Rss':
          - regex: '.. .. .. .. .. (..) .. .. .. ..'
            value: $1
          '_Lrs':
          - regex: '.. .. .. .. .. .. (..) .. .. ..'
            value: $1
          '_Rrs':
          - regex: '.. .. .. .. .. .. .. (..) .. ..'
            value: $1
          '_Lts':
          - regex: '.. .. .. .. .. .. .. .. (..) ..'
            value: $1
          '_Rts':
          - regex: '.. .. .. .. .. .. .. .. .. (..)'
            value: $1

[Brian Candler]

I don't think the exporter can do that, although it sounds like a good idea to me (i.e. to be able to set a label rather than mangle the metric name).

Possibly you could use metric_relabel_configs to fix it up:

- source_labels: [__name__]
  regex: '.*_CHANNEL_(.+)'

  target_label: channel

- source_labels: [__name__]

  regex: '(.*)_CHANNEL_.+'

  target_label: __name__

Otherwise, a simple HTTP proxy which sits between prometheus and snmp_exporter.

[Elliott Balsley]

Thanks, that relabel config works perfectly!