Forum Discussion

Jason_Hook_4092's avatar
Jason_Hook_4092
Icon for Nimbostratus rankNimbostratus
Dec 08, 2009

Does Applying an iRule cause an outage of the VIP?

Sorry if this was posted before, I wasn't having luck searching...

 

 

If I have a active Virtual Server handling many requests per second, if I use the web UI and add an iRule (when there was none) to the VIP...when I click Finished on the screen will the VIP cycle? Will any request in flight be dropped or will a new connection/request coming in at the exact same time I apply the iRule be blocked/fail?

 

 

Please assume the iRule is 100% good...

 

 

The iRule looks at a HTTP header and chooses a pool based on the value...

 

 

Thoughts?

 

 

Hard evidence/documentation stating one way or the other? I am being asked about risk level during the actual implementation and I want to say none, but I need help answering...will there be even a blip?

 

 

Thanks!

 

 

Jason
application delivery
dev
devops
iRules
  • hoolio's avatar
    hoolio
    Icon for Cirrostratus rankCirrostratus
    Dec 08, 2009
    Hi Jason,

     

     

    I believe that when you add an iRule to a VIP, all existing connections are preserved. However, the events of the iRule are applied to all existing connections.

     

     

    The main issue I've seen is run time errors occurring with existing connections if the iRule expects variables to exist that wouldn't have been created in iRule events which weren't triggered for the connection. If you're simply selecting a pool based on a header, I wouldn't expect any issues.

     

     

    However, it's always good if you can schedule a change window when making changes. You could also test the iRule on a test VIP by running looping curl or apache bench (man ab) against the VIP while adding the iRule.

     

     

    Aaron
  • Jason_Hook_4092's avatar
    Jason_Hook_4092
    Icon for Nimbostratus rankNimbostratus
    Dec 08, 2009
    Thanks Aaron,

     

     

    I was understanding the same thing...with how basic the iRule, I wouldn't expect any issues either, I just wanted to hear from someone else that existing connections are preserved and not severed with the VIP cycling or some other "outage" like experience.

     

     

    I have tested it with our development Big-IP (all our LBs are v10) and I didn't see any problems, just wanted to bounce it off others.

     

     

    Thanks again!

     

     

    Jason