Forum Discussion

Sarah's avatar
Sarah
Icon for Cirrus rankCirrus
Dec 21, 2023

iRule - unexpected behavior

Hello Community, I have recently experienced an unexpected behavior from an iRule, where the http responses were intermittent and failure detected on the last event in the iRule HTTP_RESPONSE_RELEAS...
application delivery
failure
http_response_release
ipfix
irule
zamroni777's avatar
zamroni777
Icon for Nacreous rankNacreous
Dec 22, 2023

how long is the timeout value of the ipfix pool's health monitor?

you might also try tcl async::exec for the "IPFIX::destination send ..." so http response forwarding to client doesnt need to wait for the completion of the ipfix transmission
https://wiki.tcl-lang.org/55225#pagetoc7f911216

  • Sarah's avatar
    Sarah
    Icon for Cirrus rankCirrus
    Dec 22, 2023

    Hi zamroni,

    I was using the default udp health monitor (timeout 16).

    if "IPFIX::destination send" waits for the completion of the ipfix transmission, why do you think the http responses were intermittent since the pool went down? i suspected it will affect all responses. 

    the ipfix pool was down for a while, which in result affected the application response stability, where the iRule was applied to.

    and it only got fixed when I removed the health monitor from the pool.

    • zamroni777's avatar
      zamroni777
      Icon for Nacreous rankNacreous
      Dec 23, 2023

      HTTP_RESPONSE_RELEASE is triggered when f5 is about to release data to client.
      https://clouddocs.f5.com/api/irules/HTTP-RESPONSE-RELEASE.html

      which means f5 will execute the commands in your irules before sending response to client.

      is the ipfix server health status flappy (intermittently ok / not ok) when the health monitor was applied?

      • Sarah's avatar
        Sarah
        Icon for Cirrus rankCirrus
        Dec 23, 2023

         

        The ipfix server totally knockout at that time, there was no flapping.

        Here's why i'm questioning the intermittent behaviour of the http responses on the clientside, could this possibly have to do with a specific type of responses or maybe a present of an http header made the irule act funky?

        It is worth to mention two minutes after the ipfix server went down a TCL error logged mentioning the last line "IPFIX::destination send .. " , and it appeared that minute only.

        whereas in the irule statistics, the failure stats was increasing for the HTTP_RESPONSE_RELEASE event.

  • LynnHuff's avatar
    LynnHuff
    Icon for Nimbostratus rankNimbostratus
    Jan 10, 2024

    Thank you for the link.