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BaltoStar_12467's avatar
BaltoStar_12467
Mar 12, 2015

BIG-IP : expected behavior of redirects in irule stack

F5 BIG-IP Virtual Edition v11.4.1 (Build 635.0) LTM on ESXi

My virtual-server has an iRule stack. In the top-level iRule ( highest-priority, lowest numerical priority), under certain conditions I set the destination pool and perform redirects ( 301 302 ) : 

"mysite.com" {
    pool mysite.com-pool-01
}
"mysite.co.uk" {
    HTTP::respond 301 Location "http://www.mysite.co.uk[HTTP::uri]"
}
"www.mysite.com.mx" {
    HTTP::redirect "http://www.mysite.com/default.aspx?c=6"
}

I know that destination pool can be reset in subsequent iRules -- and so final route might be to a different pool.

But what is expected behavior with respect to redirects ? Once 

HTTP::redirect
or 
HTTP::respond
is issued, is this route immediately acted upon ? ( i.e. no further iRule processing occurs ) Or is it possible that subsequent iRule could effect a different response ?

application delivery
BIG-IP
design
devops
irule
iRules
LTM

3 Replies

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  • nathe's avatar
    nathe
    Icon for Cirrocumulus rankCirrocumulus
    Mar 12, 2015

    HTTP::redirect and HTTP::respond are commands so the irule will issue that command and the browser, in this case, will perform the command. So, because they are client side cmds, in effect, the subsequent cmds won't be actioned, unless the redirect points back to the same VIP and irule.

     

    Hope this is true,

     

    N

     

  • nitass's avatar
    nitass
    Icon for Employee rankEmployee
    Mar 13, 2015

    Once HTTP::redirect or HTTP::respond is issued, is this route immediately acted upon ? ( i.e. no further iRule processing occurs )

     

    no, further irule will still be triggered.

     

    Or is it possible that subsequent iRule could effect a different response ?

     

    yes

     

    generally what people do is either to disable further event (event disable command) or perform action on the last (lowest priority) irule (set variable in higher priority irule but execute command in the lowest one).

     

    event

     

    https://devcentral.f5.com/wiki/iRules.event.ashx

     

  • Arie's avatar
    Arie
    Icon for Altostratus rankAltostratus
    Mar 14, 2015

    If a single criterion applies to multiple responses (i.e. HTTP::redirect and HTTP::respond) you will encounter an exception. In browsers this is usually displayed as "connection reset" and in the error logs you'll see entries for "multiple responses".

    In addition to 

    event disable
    (which I do not prefer because it universally halts all further processing) and executing the actual command last there is a third option: using a semaphore.