[collectd] struggling with oid that returns four values

[ryanL]

hi,

i am struggling getting this to index cleanly into whisper files, and
i'm not quite sure why. i'm noticing this error in log:

Nov  1 23:12:20 test-app-1 collectd[11197]: snmp plugin:
csnmp_instance_list_add failed.
Nov  1 23:13:20 test-app-1 collectd[11197]: snmp plugin:
csnmp_instance_list_add failed.

when polling my test switch for queue drops, i use this mib::oid pair:

JUNIPER-COS-MIB::jnxCosIfqTailDropPktRate

snmpwalk will return four values for the default switch port queues:

JUNIPER-COS-MIB::jnxCosIfqTailDropPktRate.650."best-effort" = Counter64: 0
JUNIPER-COS-MIB::jnxCosIfqTailDropPktRate.650."network-control" = Counter64: 0
JUNIPER-COS-MIB::jnxCosIfqTailDropPktRate.650."assured-forwarding" =
Counter64: 0
JUNIPER-COS-MIB::jnxCosIfqTailDropPktRate.650."expedited-forwarding" =
Counter64: 0

with the following in my types.db.custom:

ex_q_drop drops:COUNTER:0:U

and this in my collectd.conf:

   <Data "ex_q_drop">
        Type "ex_q_drop"
        Table true
        Instance "IF-MIB::ifName"
        Values "JUNIPER-COS-MIB::jnxCosIfqTailDropPkts"
   </Data>

i had though maybe i could index them against the ifName or ifDesc
value much like std_traffic, but this seems to generate the error.
when i comment out the instance, the query works but generates an
awful lot of whisper buckets (as would be expected):

root at test-app-1 etc # ls /opt/graphite/storage/whisper/fsaa-rs1/snmp/
Display all 267 possibilities? (y or n)
ex_q_drop-504_20_101_120_112_101_100_105_116_101_100_45_102_111_114_119_/
ex_q_drop-506_11_98_101_115_116_45_101_102_102_111_114_116/
ex_q_drop-510_18_97_115_115_117_114_101_100_45_102_111_114_119_97_114_100/
ex_q_drop-520_18_97_115_115_117_114_101_100_45_102_111_114_119_97_114_100/
ex_q_drop-522_11_98_101_115_116_45_101_102_102_111_114_116/
ex_q_drop-522_15_110_101_116_119_111_114_107_45_99_111_110_116_114_111_/
ex_q_drop-524_20_101_120_112_101_100_105_116_101_100_45_102_111_114_119_/
ex_q_drop-530_18_97_115_115_117_114_101_100_45_102_111_114_119_97_114
<snip>

wondering if anyone could clue me on what i'm doing wrong, or how to
work around this.

could i potentially add this oid to the std_traffic data block and add
an extra value to std_traffic in types.db? (i'll probably try this
next for fun, anyhow).

thanks!

ryan