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Romel_77740's avatar
Icon for Nimbostratus rankNimbostratus
Nov 15, 2011

irule performance question

Is it better to have 10 different irules applied to the same virtual server that do similar thing or is it better to combine in one script? Or either way doesn't matter? Eg pseudo scripts with 26 irules:::


irule A: if (src ip then pool A


irule B: if (src ip then pool B




irule Z: if (src ip then pool Z




Or is it better to do:


just 1 irule:: if (src ip then pool A else if src ip then pool B... else pool Z (or do a case statement for this in a single irule)


4 Replies

  • if we code the irule something like this, will a number of irule reduce?



    [root@ve1023:Active] config  b virtual bar list
    virtual bar {
       snat automap
       pool foo
       ip protocol tcp
       rules myrule
    [root@ve1023:Active] config  b rule myrule list
    rule myrule {
       when CLIENT_ACCEPTED {
            if {[class match -- [IP::client_addr] equals xyz]} {
                    log local0. "client is [IP::client_addr]:[TCP::client_port], action is [class match -value [IP::client_addr] equals xyz]"
    [root@ve1023:Active] config  b class xyz list
    class xyz {
          network { "action2" }
          host { "action1" }
    [root@ve1023:Active] config  tail -f /var/log/ltm
    Nov 15 08:48:30 local/tmm info tmm[4766]: Rule myrule : client is, action is action1
    Nov 15 08:48:38 local/tmm info tmm[4766]: Rule myrule : client is, action is action2
  • Hi Romel,



    If multiple iRules are applied to a Virtual Server the iRules are "combined" at runtime by the iRule Priority assigned to the iRule.



    If no priority is set then the iRules per event are added in the order that the iRules are applied to the Virtual Server.



    iRules with no Priority Applied -



    iRule 1:


    when HTTP_REQUEST {


    do something...





    iRule 2:


    when HTTP_REQUEST {


    do something else...





    They would be processed as:


    when HTTP_REQUEST {


    do something...


    do something else...





    The same holds true for other events. So it is a matter of what works best for you.



    Hope this helps.
  • Hamish's avatar
    Icon for Cirrocumulus rankCirrocumulus
    Also, when the iRUles are combined, the namespace is shared. So a variable called $MyVar in iRule1 will be the SAME variable in iRule2...



    e.g. If you init to 1 in CLIENT_CONNECT in both iRule1, then to 2 in CLIENT_CONNECT in iRule2, when HTTP_REQUEST fires in iRUle 1, the variable will have the value of 2... Not 1...



  • Excellent Point Hamish.



    I have seen instances where the first iRule contains nothing but the variable settings used in all of the other attached iRules (so that if there was a Variable Change it only had to be made in a single iRule instead of every iRule attached to a Virtual Server.