Implementing Low-Latency Electronic Trading with FIX load balancing

when FIX_HEADER {
    set MsgType [FIX::tag get 35]
    if { $MsgType eq "A" } {  # an A message is a logon message
        # record the sender and the target
        set SenderCompID [FIX::tag get 49]
        set TargetCompID [FIX::tag get 56]
        
        # log the event locally - a new FIX stream is being created
        log "FIX header: Sender $SenderCompID, Target $TargetCompID"
        
        # log the event with High Speed Logging (HSL), too
        set hsl [HSL::open -proto UDP -pool syslog_server_pool]
        HSL::send $hsl "[IP::client_addr]: Sender $SenderCompID, Target $TargetCompID\n"
        
        # choose a server pool based on the name of the sender
        switch $SenderCompID {
            "Fred's Bank"   { pool FIX1 }
            "Wilma's Bank"  { pool FIX2 }
            "Barney's Bank" { pool FIX3 }
        }
    }
}                

when CLIENT_ACCEPTED {
    # prepare for releasing the flow down to the ePVA
    BIGTCP::release_flow
}

when FIX_HEADER {
    # (same as above example, with an additional sender)
    set MsgType [FIX::tag get 35]
    if { $MsgType eq "A" } {  # an A message is a logon message
        # record the sender and the target
        set SenderCompID [FIX::tag get 49]
        set TargetCompID [FIX::tag get 56]
        
        # log the event - a new FIX stream is being created
        log "FIX header: Sender $SenderCompID, Target $TargetCompID"
        
        # choose a server pool based on the name of the sender
        switch $SenderCompID {
            "Fred's Bank"      { pool FIX1 }
            "Wilma's Bank"     { pool FIX2 }
            "Barney's Bank"    { pool FIX3 }
            "Mr. Slate's Bank" { pool FIX4 }
        }
    }
}

when SERVER_CONNECTED {
    if {$SenderCompID eq "Mr. Slate's Bank"}{ 
        # Mr. Slate's Bank sent this, so lower the latency
        log local0. "Detected $SenderCompID - releasing flow to ePVA"
        BIGTCP::release_flow
    }
}