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santosh_81454's avatar
santosh_81454
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May 14, 2012

Latency on First HTTP request.

We are load balancing a web sphere server running multiple instances. (Each instance of the server is running on different port and hence we have created the instances as pool members).

 

We have configured SNATS to overcome Asymmetric routing to this server.

 

 

There are other servers, which will pull data from the load balanced instances by connecting to the VIP. The apps that are configured on the servers that call the VIP are designed for a timeout value of 50ms.

 

 

Our issue is, the initial request to the VIP is taking around 2000ms (not 2000 always, but it varies between 2sec to 9 Sec) to be processed, but the consecutive requests are processed within 22 - 35 ms.

 

 

Not sure, why the first request is taking longer time. Did anyone face similar issue ? How to resolve the latency issue for the first request ?

 

 

(We are running the LTM on VCMP of Virpion - V11.1 HF2. LB method used for the pool is Round Robin. )

 

 

Any help is greatly appreciated.

 

 

Thanks,

 

Santosh.

 

config
design

4 Replies

  • SLowes_85801's avatar
    SLowes_85801
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    May 14, 2012
    We had the same issue with IIS server. There is an inactivity timeout on the Application Pool of 20 or 40 min, can't remember which. After the timeout is reached, the App Pool is shut down. The next connection will wake up the App Pool but takes several seconds to wake up. Maybe a similar issue with WebSphere?

     

     

    I set a custom HTTP monitor to poll a file (a .aspx script in our case), which acts as a health monitor as usual, but also keeps the App Pool alive.
  • santosh_81454's avatar
    santosh_81454
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    May 14, 2012
    Hi Slowes,

     

     

    Thanks for sharing what you have experienced. I will try to implement a monitor and see if it helps.

     

     

    Thanks,

     

    Santosh.
  • L4L7_53191's avatar
    L4L7_53191
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    May 17, 2012
    Santosh: Back in my WebSphere days we ran into this (same with Orion - I know I am dating myself :) and TomCat) on the *first* call into an application server after a restart. There was some sort of class loading going on, but only on the first invocation of a servlet. Subsequent calls were fast.

     

     

    May be worth looking into in your case too.
  • santosh_81454's avatar
    santosh_81454
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    May 18, 2012
    Thanks for your inputs L4L7.

     

     

    To see if the F5 is causing latency, we have bypassed F5 and made a direct connection to the server. Even then the initial hit was delayed. The loading of the class files make sense. We have also raise a case with the vendor of the app to see the actual cause for the behavior. We are working with them currently.

     

     

    - Santosh.