Allow poller-wrapper.py to exclude polling on device(s) based on CIDR parameters

Mike/Landy is currently working on implementing this featureset into the base poller wrapper. Be careful when updating, since this patch will likely break soon.

This feature was something we needed very, very, very, very much.

We manages variety of servers and they are divided into completely different countries or regions.
Therefore scale-up of the poller server was no longer able to handle issues such as server load and network delay, and it needed a way to separate poller.

We could get a good idea about how to separate poller at the below URL.
(http://blog.best-practice.se/2017/10/scaling-observium-horizontally.html)
But what the URL introduced was how to divide the poller instance.
We couldn't meet all of our requirements.
Because we wanted to separate poller into different regions.

Of course, it should be considered carefully to run a remote poller as Adam Armstrong suggests.
it's because all the network environment isn't good.
However, we think that we can prepare for loss of data by arrange the relay server in the middle.

Anyway, we were able to solve the problem completely with this patch.
We finally got the results that what we wanted.
I'm very grateful to Fadly Tabrani for providing this patch.

This is amazing! I really needed this feature. Now I can poll by location, os, and even syscontact. Thanks a lot!

We would only accept such a feature if it was well thought out and useful to more than one person. It's structural suicide to accept every random idea.

You don't seem to have added the ability to exclude a location, which would seem to be important.

In any event. I think it's more useful to be able to do this sort of thing in the Web UI. We've previously discussed ways of doing this, but we've not really had any instances where it's been necessary.

In general one should think very carefully about having remote pollers, since SNMP is designed to travel long distances, but MySQL and storage protocols are not.

You shouldn't be using IPs in Observium. Thus this whole concept makes little sense.

Just a thought, since location info is already stored in the device table, could it be used to limit polled devices instead since using CIDR as that would need additional IP resolution. 

For example 

poller-wrapper.py -locaton dc1 

poller-wrapper.py -location dc3 dc4

I believe the functionality to filter devices to be polled is already present based on host names and the reason in code explains it well. 

poller-wrapper.py

"Additionally, if a hostname wildcard is passed, add it to the where clause. This is
important in cases where you have pollers distributed geographically and want to limit
pollers to polling hosts matching their geographic naming scheme."
 
It would be nice to extend this feature to based on CIDRs as this is normally how the network is segmented.
 
For example, a poller servicing a location with the 10.1.0.0/16 subnet and another servicing the 10.2.0.0/16 subnet.
 

Which sense would it have? I don't see any advantage with this feature.