Message based load balancing connection status

Hi Vincent,

 

 

(1) When there are no active members in the pool (all backend nodes are down), how can I close the client connection?

 

 

you may try this way...

 

note that return value of active_members may not be the same as number of current active connection for the particular client connection.

 

 

you could keep track that by using variable. here are 2 examples

 

 

 example I
when CLIENT_ACCEPTED {
     check every second
    after 1000 -periodic {
        if { [active_members [LB::server pool]] == 0 } {
            reject
            log local0. "TCP connection closed to [TCP::local_port]."
        }
    }
}
 example II
when CLIENT_ACCEPTED {
    array set server_array {}
     check every second
    after 2000 -periodic {
        if { [array size server_array] == 0 } {
            reject
            log local0. "TCP connection closed to [TCP::local_port]."
        }
    }
}
when SERVER_CONNECTED {
    set s "[IP::remote_addr] [TCP::remote_port]"
    set server_array($s) 1
}
when SERVER_CLOSED {
    set s "[IP::remote_addr] [TCP::remote_port]"
    unset server_array($s)
}

 

 

(2) to periodically send somethig to server every 30 seconds, you can do as follow

 

 

 

 

when SERVER_CONNECTED {

 

send ping every 30 seconds

 

after 30000 -periodic {

 

you could add some code to check idletime here...

 

TCP::respond $static::conn_ping

 

}

 

}

 

 

 

 

 

May I ask what is your use case that you are using mblb profile for?

 

This information would help us improve future version of mblb profile 🙂

 

 

Thanks,

 

Nat

 

v

Thanks Nat for the suggestions.

 

 

For issue (1), I used the example 1, and the issue is resolved.

 

 

For issue (2), the example doesn't help. The main purpose for perioldically sending ping message is to handle node restart or new node join the pool when server side sending request message and waiting for response (I explain my requirement below).

 

 

I am implement a high availablity solution for a finanical product.

 

The communication is message based. One persistent client connection will be handled by multiple backend servers.

 

The message format we are using is private (2 bytes binary header + binary payload). We will do load balancing based on one field in the message.

 

 

The message can be either started from client side (client send request and wait for response) or server side (server send request and wait for response).

 

 

The issue (2) I have is for server side sending request and waiting for response. When accepting client connection, I send ping message to each active member, so there will be a connection with every active member, each member can use this connection to send request. But if one member is brought down and restart, there will be no connection between LTM and the newly started member because the client will not send request and pool to the newly started node. So I tried to send ping message perioldically, so if there is new active member, a connection could be created with the member.

 

I tried to set send ping message perioldically in CLIENT_ACCEPT:

 

when CLIENT_ACCEPTED {

 

log local0. "Client [IP::remote_addr]:[TCP::remote_port]-[TCP::local_port]"

 

if {[active_members [LB::server pool]] < 1} {

 

reject

 

return

 

}

 

broadcast connect message to backend servers

 

foreach m [active_members -list [LB::server pool]] {

 

log local0. "send connect to $m"

 

after 500

 

pool [LB::server pool] member [lindex $m 0] [lindex $m 1]

 

TCP::payload replace 0 0 $static::conn_ping

 

TCP::release 2

 

TCP::notify request

 

}

 

 

check every second

 

after 2000 -periodic {

 

if { [active_members [LB::server pool]] == 0 } {

 

reject

 

log local0. "TCP connection closed to [TCP::local_port]."

 

}

 

}

 

Check whethere there is new member

 

after 30000 -periodic {

 

foreach am [active_members -list [LB::server pool]] {

 

pool [LB::server pool] member [lindex $am 0] [lindex $am 1]

 

log local0. "send status ping to $am"

 

TCP::payload replace 0 0 $static::conn_ping

 

TCP::release 2

 

TCP::notify request

 

}

 

}

 

 

TCP::collect

 

}

 

 

but I got error:

 

 

Apr 18 12:52:01 local/tmm2 err tmm2[5551]: 01220001:3: TCL error: CAM-MBLB - Address in use (line 2) invoked from within "pool [LB::server pool] member [lindex $am 0] [lindex $am 1]" ("foreach" body line 2) invoked from within "foreach am [active_members -list [LB::server pool]] { pool [LB::server pool] member [lindex $am 0] [lindex $am 1] log local0. ..."

 

 

Is there any way to solve this kind of issue?