Priority group activation and automatically closing connections when higher priorty group goes UP.

chmod +x /var/tmp/delete_backserver_session.sh

Because the 120 seconds delay depends on tcp monitor use "tcp_delay_up_120s" and its value of "Time Until Up" set to 120s. You can use tcl script tmsh:: delete to delete a session. The Linux shell is not mandatory

the file in /config/  directory will save in ucs，user_alert.conf and icall config also save in ucs file

In my test environment, six Cisco routers enable the telnet service, a bip IP VE. When I close the telnet service of the three primary nodes, and then the client telnet VS, I manage the router of the backup node, and then enable the telnet service of the primary node to simulate the recovery of the primary node. During the 120 seconds, I execute the show running command. After about 120 seconds, I will be reset tcp connection

pool_server has 6 pool members,  (A,B,C) group priortity is 10; (D,E,F) group priority is 5, tcp monitor use "tcp_delay_up_120s" and its value of "Time Until Up"  set 120s;

pool_icall members is (A,B,C), use default tcp monitor

pool_back members is (D,E,F), use default tcp monitor

user_alert.conf

alert poolserver-1-UP "Pool /Common/pool_server member /Common/192.168.100.1:23 monitor status up" {
        exec command="tmsh generate sys icall event delete_backserver_session context { { name poolname value pool_ic
all } }"
}
alert poolserver-2-UP "Pool /Common/pool_server member /Common/192.168.100.2:23 monitor status up" {
        exec command="tmsh generate sys icall event delete_backserver_session context { { name poolname value pool_ic
all } }"
}
alert poolserver-3-UP "Pool /Common/pool_server member /Common/192.168.100.3:23 monitor status up" {
        exec command="tmsh generate sys icall event delete_backserver_session context { { name poolname value pool_ic
all } }"
}

 icall config:

list sys icall handler triggered delete_backserver_session 
sys icall handler triggered delete_backserver_session {
    script delete_backserver_session
    subscriptions {
        delete_backserver_session {
            event-name delete_backserver_session
        }
    }
}

list sys icall script delete_backserver_session           
sys icall script delete_backserver_session {
    app-service none
    definition {
        foreach var {poolname} {
            set $var $EVENT::context($var)
        }
        puts "poolname is $poolname"
        exec /bin/bash /var/tmp/delete_backserver_session.sh
    }
    description none
    events none
}

chmod +x /var/tmp/delete_backserver_session.sh

#!/bin/bash
count=`tmsh list ltm pool pool_icall | grep "state up" | wc -l`
if [ $count -ge 2 ] 
then 
        for i in `tmsh show ltm pool pool_back members | grep -E "Ltm::Pool Member:" | awk '{print $NF}'`
        do 
                address=`echo $i | awk -F ":" '{print $1}'`;
                port=`echo $i | awk -F ":" '{print $2}'`
                tmsh delete sys connection ss-server-addr $address ss-server-port $port
        done
fi

To meet your needs, you must use icall and user_ alert.conf

pool_server has 6 pool members,  (A,B,C) group priortity is 10; (D,E,F) group priority is 5:

ltm pool pool_server {
    members {
        192.168.100.1:telnet {
            address 192.168.100.1
            priority-group 10
            session monitor-enabled
            state up
        }
        192.168.100.11:telnet {
            address 192.168.100.11
            priority-group 5
            session monitor-enabled
            state up
        }
        192.168.100.12:telnet {
            address 192.168.100.12
            priority-group 5
            session monitor-enabled
            state up
        }
        192.168.100.13:telnet {
            address 192.168.100.13
            priority-group 5
            session monitor-enabled
            state up
        }
        192.168.100.2:telnet {
            address 192.168.100.2
            priority-group 10
            session monitor-enabled
            state up
        }
        192.168.100.3:telnet {
            address 192.168.100.3
            priority-group 10
            session monitor-enabled
            state up
        }
    }
    min-active-members 2
    monitor tcp
}

The master member has A, B and C(firstly create a icall_pool its pool member is A,B,C). You also have to create three pools (pool_icall-1, pool_ical-2, and pool_icall-3). The members are (A, B), (A, C), and (B, C) respectively

pool_back members is (D,E,F)

user_alert.conf

alert poolicall-1-DOWN "No members available for pool /Common/pool_icall-1" {
        exec command="tmsh generate sys icall event delete_backserver_session context { { name poolname value pool_ic
all } }"
}
alert poolicall-2-DOWN "No members available for pool /Common/pool_icall-2" {
        exec command="tmsh generate sys icall event delete_backserver_session context { { name poolname value pool_ic
all } }"
}
alert poolicall-3-DOWN "No members available for pool /Common/pool_icall-3" {
        exec command="tmsh generate sys icall event delete_backserver_session context { { name poolname value pool_ic
all } }"
}

When any of the pools has no available members, an icall event is triggered. Execute the exec linux shell in the icall script (icall script is based on tcl and wants to sleep for 120 seconds, and then execute the session action of deleting the standby node. Later, the test found that icall script deleted the after xxx ms {script} function of tcl, and cannot execute the after function. Instead, we call  use exec linux shell

#!/bin/bash
#sleep 120;
count=`tmsh list ltm pool pool_icall | grep "state up" | wc -l`
if [ $count -ge 2 ] 
then 
        for i in `tmsh show ltm pool pool_back members | grep -E "Ltm::Pool Member:" | awk '{print $NF}'`
        do 
                address=`echo $i | awk -F ":" '{print $1}'`;
                port=`echo $i | awk -F ":" '{print $2}'`
                tmsh delete sys connection ss-server-addr $address ss-server-port $port
        done
fi

 icall config:

list sys icall handler triggered delete_backserver_session 
sys icall handler triggered delete_backserver_session {
    script delete_backserver_session
    subscriptions {
        delete_backserver_session {
            event-name delete_backserver_session
        }
    }
}

list sys icall script delete_backserver_session           
sys icall script delete_backserver_session {
    app-service none
    definition {
        foreach var {poolname} {
            set $var $EVENT::context($var)
        }
        puts "poolname is $poolname"
        exec /bin/bash /var/tmp/delete_backserver_session.sh
    }
    description none
    events none
}

Question to your scenario: Do your application have to maintain a server side session state which require the use of what F5 is calling "Session Persistence", or are your application absolutly fine if request from the same client is per-request load balanced to the available online nodes?

Depending on the requirement of persistence, you would either need to create a GUI based setup via OneConnect (to enable per-request balacing) and Pool- and Monitor-Settings. Or you may end up with a custom iRule to handle the closing of such persistet sessions if your primary/backup systems are failover/fallback.

Cheers, Kai

Hi Asura2006 , 
The default behavior of Priority group Activation is when the Backup PG activated it handles your connections , but when higher PG is returned UP and active again , all comming new connections is handled by "main" PGA and the Backup PG handles only Active connections till it completes. 
I see this is a good behavior to be done by PGAs and this is the default. 

If you see that the new connections don’t be handled by "main" PG when it became actve , check if you enable " manual resume " option under assigned monitor configuration. 

> Do you want to transfer active connections to be handled by "main"PG when it became available again ?
specify more please in this section. 

Regards