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Stefan_Klotz's avatar
Stefan_Klotz
Icon for Cumulonimbus rankCumulonimbus
Mar 10, 2014

Issue with HTTP session limit iRule

Hi there, we are using the "HTTP session limit"-iRule from devcentral and it seems this caused an issue in our environment. During a disaster recovery test we disabled the standby-LB (disabled all interfaces), which caused the VS with the mentioned iRule assigned to redirect to the specified maintenance URL. The variable "static::max_active_clients" in this iRule is set to 10000 and it's very unlikely that we had such an amount of connections during the test. We are also not sure if this is really related to the disconnect of the standby-LB or if Murphy said hello. But at the time when we re-enabled the standby-LB again, the website was back online and no maintenance page was displayed. At the moment we also have no idea how to further troubleshot or analyze this, also due to the fact that trying to reproduce the error (by disabling the standby-LB again) isn't an option. So that's why we ask you to see if someone has any kind of idea of what could be the root cause or which steps or tests could be done to further troubleshoot this issue. Thank you!

 

Ciao Stefan :)

 

application delivery
devops
iRules
LTM

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  • Christian_30338's avatar
    Christian_30338
    Historic F5 Account
    Mar 11, 2014

    Hi Stefan,

     

    Here are some ideas on further troubleshooting this to understand what happened. Firstly the easiest way to create a similar environment if you can't touch production is via the F5 Virtual Edition. Then you can take the existing interface configuration iRule and modify the iRule thresholds to something you can easily replicate. Once this is in place adding logging to the iRule will allow you to see what actions are being taken and why.

     

    Hope this helps. Christian