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Forum Discussion

R_Marc's avatar
R_Marc
Icon for Nimbostratus rankNimbostratus
Apr 28, 2014

Odd behavior on regsub in iRule

I have a switch in an irule to clean up some bad decisions made by developers. Here is the trimmed down version where the problem occurs, with some debug logging. ltm rule rmarc-test-rule { ...
application delivery
devops
iRules
Patrik_Jonsson's avatar
Patrik_Jonsson
Icon for MVP rankMVP
Apr 29, 2014

Hi!

Maybe this is not the answer you're looking for, in which case we can adjust it a bit.

A few suggestions:

  • Try to avoid the -sub switch if you can as it demotes the LB to a use single core processing.
  • Use the is_redirect check to avoid using costly regsub commands in vain.

A rule suggestion (providing that you will always replace the location with the same url):

when HTTP_RESPONSE {
     Ferret out bad location headers   
    if { [HTTP::is_redirect] } {
        set location [string tolower [HTTP::header values Location]]

        if { $location contains "test" || $location contains "a401" } {
            log local0. "Header before: [HTTP::header values Location]"
            HTTP::header replace Location "dtl.somedomain.com"
            log local0. "Header after: [HTTP::header values Location]"          
        }
    }
}

/Patrik