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vkpopuri_96841's avatar
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Apr 02, 2012

F5- Load balancing questions




In a typical web server load balancing scenario with Round Robin, we would like to make sure that a minimum number of servers are online at any given point of time, say 50% servers should be online all the time.For example, if there are 6 member servers on a VIP, 3 servers have to be online all the time or raise an alert if more than 50% have to be marked offline. Is it possible to include code to send an alert in the probe file to get the number of current healthy servers and the number of total servers in the pool and use this information for triggering an alert in case the load balancer has to take more than 50% servers offline? This alert will help in the operational folks in dealing with the situation.











2 Replies

  • Hi Vkpopuri,



    Under Pool memebers you can enable the Priority group activation.and give the number of servers you want to recive the traffic. In your case you can provide with the number 3, Basically what happens is if the servers in pool members goes down less then 3 then the back up server comes in to picture.



    And Their is a way to setup your BIG IP to generate a msg if your server fails on the probe( can be done through irule also). Hope this helps.



  • Thanks Kevin. I more interested in handling capacity issues. I was thinking whether we can include code need to take care of this. Is the below doable using a probe file?



    1. Send a GET request to F5- API (iControl?) and get the information for current member status information. This information can be used to find out the ratio of online/total number machines.


    2. The probe based on a synthetic transaction finds that a particular server is returning 500 error.


    3. Based on the http status code 500, load balancer decides to take the fauly server offline.It needs to check how many servers are online at that time, the number of servers or percentage could be hard-coded like 50%.


    4. The load balancer marks the faulty server offline and will also send an alert that not enough number of servers are online in case the percentage goes below 50%.