LVS Change weight on Load (lvs-cwol)

Author: Léon Keijser - [email protected]


Description:
============
Set of client/server python scripts to have a realserver
report its Load to the director and have it change its
weight accordingly.

Usage:
======
You simply set a warning and a critical threshold in the
server.py and run it on the director. Run the client.py 
component on a realserver and it reports its load back to
the director. 

Then the director checks if the realserver occurs in its
LVS table, checks if it reaches a threshold and changes
the weight of the realserver if it does.

For example:

In the LVS table is an entry:

Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.168.1.100:80 wlc
  -> 192.168.1.11:80              Route   100    0          0

The server.py stores the entry like this:

{ RIP = [VIP, WEIGHT, WEIGHTCURRENT, VPORT, RPORT] }

Now when server.py starts, it stores the entry like this:

192.168.1.11 = 192.168.1.100, 100, 100, 80, 80

When client.py (ran on the realserver) connects, server.py
checks if the Load reported by the realserver doesn't exceed
the 'critical' threshold yet. If it doesn't, it checks if the
'warning' threshold is reached. If not, nothing happens. If
one of the thresholds is reached, the server.py changes the
weight of the realserver (-25% for warning, -50% for critical).
As soon as the load goes back to normal, the weight is set
back to the original value.