Launching soon: The world's first vendor agnostic bug scrubLearn more & join waitlist
OPERATIONAL DEFECT DATABASE
...
...
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.
milkie commented on Thu, 24 Oct 2013 13:41:39 +0000: After some internal discussion, we decided that our recommendation is not to use subagents over the network. mongod as a subagent should only connect to a local snmp master. Therefore, the port number should always be a way to uniquely identify a mongod.
0.) Install standard pre-req packages for SNMP. 1.) Edit /etc/snmp/snmpd.conf and /etc/snmp/mongod.conf config files for subagent connection to snmpd through TCP:1705. 2.) Start up snmpd daemon. 3.) Launch a PSS replica set, with each running with --snmp-subagent on a distinct host and same port. 3.) Run snmpwalk against the agentaddress defined for your running snmpd daemon snmpwalk -m MONGO-MIB -v 2c -c mongodb ec2-foo-bar.amazonaws.com:1161 1.3.6.1.4.1.34601 Actual command-line flags used for each host: PRI: ./bin/mongod --replSet snmpd --snmp-subagent --port 27017 --fork --dbpath data/snmpd-0/ --logpath logs/snmpd-0/mongod.log --smallfiles --nohttpinterface --oplogSize=50 SEC: ./bin/mongod --replSet snmpd --snmp-subagent --port 27017 --fork --dbpath data/snmpd-2/ --logpath logs/snmpd-2/mongod.log --smallfiles --nohttpinterface --oplogSize=50 SEC: ./bin/mongod --replSet snmpd --snmp-subagent --port 27017 --fork --dbpath data/snmpd-4/ --logpath logs/snmpd-4/mongod.log --smallfiles --nohttpinterface --oplogSize=50