Reset session on my Virtual Server when a specific pool member with high priority come UP

Hi Cryosleep,

you may try one of the iRules below, to rebalance active sessions for ServerB if ServerA comes back online...

iRule 1: Using a per TCP-Packet

CLIENT_DATA

when RULE_INIT {
    set static::IP_ServerA "10.10.10.1%1"
    set static::IP_ServerB "10.10.10.2%1"
}
when SERVER_CONNECTED {
    if { [LB::server addr] equals $static::IP_ServerB } then {
        clientside {
            TCP::collect
        }
    }   
}
when CLIENT_DATA {
    if { [active_members -list [LB::server pool]] contains $static::IP_ServerA } then {
        LB::detach
        LB::reselect
        TCP::release
        return
    }
    TCP::release
    TCP::collect
}

iRule 2: Using a periodic TCL script on every active connections to ServerB to lookup the availability of ServerA and then failover.

when RULE_INIT {
    set static::IP_ServerA "217.110.108.152%1"
    set static::IP_ServerB "217.110.108.152%1"
    set static::reject_interval 5000 ; msec
}
when SERVER_CONNECTED {
    if { [LB::server addr] equals $static::IP_ServerB } then {
        after $static::reject_interval { 
            if { [active_members -list [LB::server pool]] contains $static::IP_ServerA } then {
                after cancel -current
                LB::detach
                LB::reselect
            }
        }
    }
}

Note: iRule 1 should be considered as very agressive for your CPU, since the status of ServerA is checked on each single TCP-Packet send from the client to ServerB (allows very fast failbacks). iRule 2 uses a once every X msec interval to check the status of ServerA for server side connection send to ServerB (less CPU hungry approach).

Note2: Both iRule are designed to keep the client side TCP-Connection active by transparently reselecting the server side side connection from ServerB to ServerA. If this is a problem for your application, then report back and I'll rewrite the iRule, to reject the client side connection.

Cheers, Kai