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Type: Bug
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Resolution: Won't Fix
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Priority: Major - P3
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None
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Affects Version/s: 2.5.3
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Component/s: Diagnostics
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Labels:
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Environment:* EC2, Amazon Linux, m1.medium
* PSS replica set
* All mongod instances running as SNMP subagents, reporting to {{snmpd}} functioning as SNMP master
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ALL
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If a replica set of SNMP subagents are all running on the same port on different hosts, then SNMP responses are ambiguous - only one "27017" entry is returned, and for which member appears to be arbitrary.
... MONGO-MIB::globalOpInsert."27017" = Counter32: 1 MONGO-MIB::globalOpQuery."27017" = Counter32: 60 MONGO-MIB::globalOpUpdate."27017" = Counter32: 1 MONGO-MIB::globalOpDelete."27017" = Counter32: 0 ... MONGO-MIB::replSetName."27017" = STRING: "snmpd" MONGO-MIB::replSetVersion."27017" = INTEGER: 3 MONGO-MIB::replIsMaster."27017" = INTEGER: 1 MONGO-MIB::replIsSecondary."27017" = INTEGER: 0 MONGO-MIB::replPrimary."27017" = STRING: "hostA:27017" MONGO-MIB::replMe."27017" = STRING: "hostA:27017"
Furthermore, if the replica set member identified by the MONGO-MIB::replMe field is brought down (in the above example, say hostA:27017 becomes unavailable), then the snmpwalk becomes unresponsive - does not return any results from any of the other members.
This behavior would seem to limit the utility of the subagent model given a "typical" replica set deployment. However of course a workaround exists to always utilize a distinct set of ports when using SNMP.