Need some advice on monitoring a weird SNMP device

[BillP]

This is my first post; please be gentle!
We have a couple of devices in our system that control other sub-devices (it's part of a cable TV data system). The sub-units don't have IP addresses but their parameters can be monitored via the master units using SNMP. The data is accessed in a very strange way by using an SNMP Set command to send the MAC address of the sub-unit; the parameter values for that sub-unit can then be accessed. I don't think Zabbix can do SNMP Set commands but I would like to be wrong.
I can write a shell script to get the data using the MAC address as a parameter but I think this will cause problems. There has to be a way to make sure that Zabbix doesn't run more than one instance of the script or the data could be assigned to the wrong device.
Even if I can do this, I'm not sure how to pass the parameters back to Zabbix - is there a defined format somewhere? XML, JSON etc.?
Bill.

[tim.mooney]

I'm not aware of any way to make Zabbix use SNMP Set currently, so I think a scripted approach is likely your best bet (again, currently).

If you go the scripted approach, your script can also be written to use some kind of locking mechanism/mutex so that only one item can be gathered at a time, to avoid the race condition. If you use locking to effectively serialize these checks, using a passive check probably isn't the way to go. An active check might work, but if I were facing this situation, I would probably not use active or passive checks: I would schedule the script to run independently and submit the data to Zabbix using the Zabbix trapper method.

There are several very experienced Zabbix admins that post on these forums, it's possible that one of them know a better method than the one I've suggested.

Also, the data format used by the various checks is described in the appendices of the manual. Some protocol exchanges are binary, but many of them use JSON. You may also be interested in reading up on zabbix_sender.

[BillP]

Thank you very much, Tim. That all sounds very sensible and solves the race problems very neatly. I will look into Zabbix trapper and read the manual appendices.
Bill.