How to use make a simple flow using SNMPSET/SNMPGET

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How to use make a simple flow using SNMPSET/SNMPGET
Append A - Troubleshooting common mistakes

Pre-requisites:
- Nifi Cluster Installed (I'm using HDF 3.1.2.0 hence with Nifi 1.5)
- Centos7

With your NIFI cluster installed, you're up to initiate this step-by-step.
First of all, we'll need to install a snmp server to retrieve/set values of/to MIB's. In my case I'm using net-snmp tool, and it comes with some MIB samples to play. Here we're going to use the SNMPv2-MIB.txt under the /usr/share/snmp/mibs path

1)Install net-snmp

yum install -y net-snmp net-snmp-utils net-snmp-libs 

2)Give full access of read-write to anyone at public community (DON'T DO IT IN PROD, please)

echo > /etc/snmp/snmpd.conf 
printf "agentAddress udp:161\nrwcommunity public\nrwuser public\nrocommunity public default system\nrouser public" >> /etc/snmp/snmpd.conf 

3)Start the SNMP SERVER DAEMON - port 161

service snmpd start 

4)Test a simple snmpwalk to see if those changes at step 2 are working

snmpwalk -v2c -mALL -c public localhost system 

5)Test a simple snmpget

snmpget -v2c -mALL -c public localhost SNMPv2-MIB::sysContact.0 

6)Setting a simple value to overwrite the value above, and check again to see if the value has been replaced with the new value

snmpset -v2c -mALL -c public localhost SNMPv2-MIB::sysContact.0 = "Vinicius Higa Murakami" 
snmpget -v2c -mALL -c public localhost SNMPv2-MIB::sysContact.0 

7)Login as nifi user and take the same steps as above (just to ensure that the nifi user has access to read/write)

su - nifi 
snmpset -v2c -mALL -c public localhost SNMPv2-MIB::sysContact.0 = "Nifi it's here" 
snmpget -v2c -mALL -c public localhost SNMPv2-MIB::sysContact.0 

8)Now we're ready to use nifi and draw the simple flow, using SNMP processors.
Go to nifi UI and draw the following components:

GenerateFlowFile Property

SetSNMP Property

LogAttribute Property

GetSNMP Property

LogAttribute Property

9)Run the nifi flow (snmpset and snmpget) and check if your value is showing up in the nifi-app.log

Append A
To troubleshoot the snmp, you can enable the DEBUG log by adding the following line to the /etc/sysconfig/snmpd

OPTIONS="-A -p /var/run/snmpd -a -LF 7 /var/log/snmpd.log" 

And then make some snmpget (step 7) to check if it's logging the connections into the /var/log/snmpd.log. Should appear 2 lines:

Connection from UDP: [127.0.0.1]:40769->[127.0.0.1]:161 
Received SNMP packet(s) from UDP: [127.0.0.1]:40769->[127.0.0.1]:161 

If you're having issues with the SNMPSET like the below.

Check if your snmpset it's able to reach the snmp server and send snmp packets, to do this, you can use tail -f /var/log/snmpd.log to monitor the connections and start the flow to watch the behaviour.
Other attention point is to check if your nifi has permissions to set/get values from MIB's (make sure you did the step 7).
And lastly is to check if your snmp$oid is valid.

And here's the template used:
template-kb-snmp.xml