Forum Discussion
sriramgd_111845
Nimbostratus
Nimbostratusinspect start of payload
We are planning to add an 'overload' iRule in production, to allow for redirect in case of overload of our application server.
We want users who are already logged to continue with t...
Sriram: Ah, that makes good sense -- I understand now. An idea to help narrow down the window of when the problem starts would be to setup a fake pool that contains the same webservers as the real pool, but setup this fake pool with a health check that simulates a login or some other database work (i.e. send a POST to the webserver that goes through to the database). This way if the database goes crazy the members in the fake pool will get marked down on BIG-IP, which means you'll get alerts right away (i.e. if the BIG-IP is configured to do SNMP traps, you'll get a trap about the fake pool members going down).
Depending on your setup, you might also be able to take advantage of this:
http://devcentral.f5.com/Wiki/default.aspx/AdvDesignConfig/ActionOnLog.html
(i.e. if you're sending alerts or syslog entries off-box, you could use ActionOnLog to start a script that helps debug the database problem, for example).
hoolio: Good idea -- I hadn't thought about it. However, it's missing the per-user randomized part of the delay -- this is desirable to overcome the 'clumping' of real user activity that tends to happen when an app is under attack. However, your method is definitely better if you don't want randomized delay -- you should put your alternative in CodeShare.
