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DannyG's avatar
DannyG
Icon for Nimbostratus rankNimbostratus
Nov 02, 2017

Help with iRule to route by host header to pool

Hello, I am trying to save public IPs with an iRule by using the hostname and mapping it to the pool. The rule came from here but I can't find the original thread but it seems to work but I wanted to make sure it is the most efficient way to do it.

 

devops
irule
iRules
  • DannyG's avatar
    DannyG
    Icon for Nimbostratus rankNimbostratus
    Nov 02, 2017

    Thanks for the help in advance!

    The datagroup will be string and be formated like hostname:poolname

    when HTTP_REQUEST {
 test_dg is a string data-group where the entries are name:value pairs
 name is the requested HTTP host header, value is the associated pool-name

     check the requested HTTP host header against entries in data-group
    if { [class match [string tolower [HTTP::host]] equals test_dg ] } {
         if the HTTP host header is in datagroup
         send the request to the pool associated with the datagroup entry
        pool [class match -value [string tolower [HTTP::host]] equals test_dg ]
    } else {
         drop the request if the host header is not in datagroup
        drop
}
}
  • Leonardo_Souza's avatar
    Leonardo_Souza
    Icon for Cirrocumulus rankCirrocumulus
    Nov 02, 2017

    Looks good to me, there is very little to optimize here.

    Reading directly from a variable like [HTTP::host] is faster than setting the value in a variable and read that variable after. However, in this case, you are also using the string tolower twice, so not sure if there will be any improvement.

    when HTTP_REQUEST {
 test_dg is a string data-group where the entries are name:value pairs
 name is the requested HTTP host header, value is the associated pool-name

     check the requested HTTP host header against entries in data-group
    set host [string tolower [HTTP::host]]
    if { [class match $host equals test_dg ] } {
         if the HTTP host header is in datagroup
         send the request to the pool associated with the datagroup entry
        pool [class match -value $host equals test_dg ]
    } else {
         drop the request if the host header is not in datagroup
        drop
}
}

    Have a look in this link about testing the speed of the iRule.

    https://devcentral.f5.com/articles/irules-optimization-101-05-evaluating-irule-performance

    If you want to read the full article:

    https://devcentral.f5.com/articles/irules-optimization-101-01-if-elseif-and-switch