iRule to check for the page content and force-offline node in a pool

Hi Venkat,

as I said, persistent session are transparently rebalanced to the next active node in the case that the persited node is unhealthy. You could check this behavior by using the iRule below. It uses the

PERSIST_DOWN

event to

[log]

persisted node that have been failed. After

PERSIST_DOWN

has been triggered, a regular

LB_SELECTED

event will occour, where one of the remaining nodes are getting selected...

when PERSIST_DOWN {
    log local0.debug "Persistent Node [LB::server addr] is marked as [LB::status]"
    set persist_down 1
}
when LB_SELECTED {
    if { [info exists persist_down] } then {
        log local0.debug "New node selection is [LB::server addr]"
        unset -nocomplain persist_down
    }
}

To kill even the active session (Remark: Active Session =/= Peristent Sessions) to your backend systems, you have to query the currently [active_members] on every single TCP packet, that is going to be send to your pool members and then trigger a TCP::close or

reject

if the currently selected node is not marked as "online"...

when SERVER_CONNECTED {
    TCP::collect
}
when SERVER_DATA {
    if { [active_members -list [LB::server pool]] contains [LB::server addr] } then {
        TCP::release
    } else {
         Use TCP::close to close the connection after the next response

        TCP::close

         User reject to terminate the request immediately

         reject 
    }
}

Note: Keep in mind, that the iRule above produces a a huge performance overhead, since the

SERVER_DATA

event and the containing script block is triggered on every single TCP packet that is send to your pool members.

Cheers, Kai

Hi Venkat,

if a node is marked as "down" by an monitor, then its comparable to set this node manually as "Force-offline", since it does not receive any new and even persistent sessions.

The

[LB::down]

command will force an fresh health monitor probe and would also mark the node temporary as "down" till the health monitor check has completed. The result of the health monitor will then keep the node "down" or flip it immediately back to "online". So i guess there is no benefit using this command...

What the is your detailed requirement and what missing when a monitor is marking a node as "down"? Should LTM also kill any ongoing sessions to this node?

Cheers, Kai