iRule for HTTP redirect, destination address persistence based on HTTP::URI

Ahh. Just found it.... An excellent solution can be found here: https://devcentral.f5.com/codeshare/election-hash-load-balancing-and-persistence

Thanks anyway!

Hi Jeroen,

you could store the previous elections results for a given URI/Path into LTMs memory based [table] and then query the [table] on consecutive request before electing again.

when RULE_INIT {
    set static::table_lifetime 86400 ; One day
}

when HTTP_REQUEST {
    if { [HTTP::path] starts_with "/vod/" } then {
        if { [set location [table lookup -notouch "redir_[HTTP::path]"]] ne "" } then {
            HTTP::redirect $location
        } else {

             Insert your election code here
             Change your code so that it stores the elected location into $location

            table set "redir_[HTTP::path]" $location indef $static::table_lifetime
            HTTP::redirect $location
        }
    }
}

Cheers, Kai

Hi Kai,

Thanks for your ideas.

Using the hash election there is no need to store the information in the memory since there will not be that many http requests hitting the LTM. It is only the first HTTP request a client makes. Consequent requests as derived from the m3u8 playlist are made to the edge server directly. So If there are say 20.000 clients in 1 hour requesting the initial m3u8 playlist then the iRule will be fired only 5.4 times per second on average (if the requests are evenly spread out) I have seen similar iRule executions well above 1000 tps. For now I have 2 edge nodes and the following iRule. For each request

 Election Hash iRule
 Version 1.0 Jan 5th 2016

 MD5 calculation of Server + URI
 Rule selects Server that scores highest

 S = Current high score
 N = Node being evaluated
 W = Winning node


when HTTP_REQUEST {       
    if {[active_members -list pool_edge_nodes] > 0 }   {
        if { (([HTTP::method] eq "GET") && ([HTTP::uri] contains ".m3u8")) } {
             Election Randomizer
             Using md5 function + http::uri to generate a score. The highest wins.
            set S ""
            set R ""
            foreach N [active_members -list pool_edge_nodes] {
            if { [md5 $N[HTTP::uri]] > $S } {
                set S [md5 $N[HTTP::uri]]
                set W $N
                }
            }
            log "winning server: $W"

             Generate redirect
            set edgeip [lindex $W 0]
            set url "http://$edgeip[HTTP::uri]"

             Send Redirect message
            HTTP::redirect "$url"
            log "[IP::client_addr] - Redirected to $url"
        } else {
             Send Service Unavailable message
            HTTP::respond 503
            log "[IP::client_addr] - Not redirected, no edge node available"
        }
    } else {
         Send Service Unavailable message
        HTTP::respond 404
        log "[IP::client_addr] - Not redirected, not a valid request"
    }
}   

Thanks,

Jeroen