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Imran_Masud_383's avatar
Imran_Masud_383
Icon for Nimbostratus rankNimbostratus
Aug 02, 2010

Resilient to faulty health check

Is it possible to create a safe net which limits the number of pool members which are taken out of service in response to a failed Http Monitor. Suppose I have pool which have 5 members for my web application. Server 1, Server2 ... Server 5. I created 5 monitors for each server. Example: http://Server1/myapp/Diagnoistic.aspx. If this diagnostic page does not return 200 then take the server/application out of the rotation. The above scenario assumes that diagnostic page is bug free and it always work. However in some cases it could happen that it generates false positives. How do I protected against this scenario? Could I create a create a Rule that ensures that at any given time F5 would just take N% of servers out of service in response to failed monitor. If the N% is 50% then F5 should only take 3 servers out of rotation at the max, even if all 5 servers are down. Thanks You Imran
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  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Aug 02, 2010
    Hi Imram,

     

     

    Not really. There isn't a way to change the inbuilt monitor behavior based on the number of available pool members compared with the total number. I suppose you could try to implement something like this in an external monitor. But in practice, I think it would be better to limit the chances that someone might break the monitor page and handle when all of the servers are truly down.

     

     

    Aaron
  • Imran_Masud_383's avatar
    Imran_Masud_383
    Icon for Nimbostratus rankNimbostratus
    Aug 02, 2010
    Thanks hoolio for prompt reply.

     

     

    Creating external monitor have its issues of maintaing N%, it is not trivial as it introduces duplication of information. I have to now know which servers are available and which servers are being used by F5 when determing N%.

     

    It would be nice if load balancers could have this feature built in.

     

     

     

     

     

  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Aug 03, 2010
    If you think it would be a useful feature to add to the product, you could open a support case and ask F5 to consider building it into LTM in a request for enhancement.

     

     

    Aaron