Friday, February 8, 2013

Monitor customized application in Windows by SNMP

The native SNMP service  in Windows can provide basic metrics like CPU, memory and disk etc, but it doesn’t have “extend” feature in net-snmp, which allows you run a script for application monitoring. Net-snmp can’t be used as replacement for Windows SNMP service because some SNMP extension agent relies on it and known issue like HOST-RESOURCES MIB doesn’t work in net-snmp. 

 The good news is that you can have net-snmp co-exist with Windows SNMP, you can have nice features like extend ability, in the mean time, pass the other functions to native Windows SNMP service.

As of Net-SNMP 5.4, the Net-SNMP agent is able to load the Windows SNMP service extension DLLs by using the Net-SNMP winExtDLL extension. The extension requires the net-snmp binary to be native (32bit net-snmp extension won’t work in 64bit Windows).

Net-snmp 64bit binary is hard to find, it seems only net-snmp-5.5.0-2 has 64bit binary pre-compiled, you might need to compile yourself for other versions. 

Install net-snmp

Run the net-snmp binary installer select “with Windows Extenstion” instead of standard agent, unselect “net-snmp trap service” and “Perl SNMP modules”, the default path is c:\usr

Configure net-snmp

Register net-snmp as Windows service

Edit c:\usr\registeragent.bat to disable modules conflicting to Windows   by adding parameter.
(Note: if system_mib is also disabled, SNMPv2-MIB::sysuptime won’t report correct time)
Run c:\usr\registeragent.bat

Edit C:\usr\etc\snmp\snmpd.conf

rocommunity public
#Test extend feature to execute a script, the script path must use Unix style ‘/’
extend userscript c:/temp/test1.bat

Start Windows service “net-snmp agent”(Native SNMP service must be stopped)


#Test standard SNMP metrics, the HOST-RESOURCES-MIB is provided by native SNMP service, not net-snmp
[root@zabbix]#/usr/bin/snmpwalk -v 2c  -c public   HOST-RESOURCES-MIB::hrSystemUptime
HOST-RESOURCES-MIB::hrSystemUptime.0 = Timeticks: (640892116) 74 days, 4:15:21.16

#The extend feature is provided by net-snmp, Execute the script by snmpwalk
[root@zabbix]#/usr/bin/snmpwalk -v 2c -Ov -c public 'NET-SNMP-EXTEND-MIB::nsExtendOutLine."userscript"'
STRING: web-time=80
STRING: web-status=[ok]


Check which Windows modules loaded, start snmpd in command line with debugging “WinExtDLL”
Snmpd.exe -I-udp,udpTable,tcp,tcpTable,icmp,ip,interfaces,snmp_mib  -DwinExtDLL 



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