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7 replies Latest Post - ‏2013-07-07T11:14:00Z by HermannSW
SystemAdmin
SystemAdmin
6772 Posts
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Pinned topic Datapower Round Robin

‏2012-12-10T05:23:34Z |
I have a quick question regarding how the 'Round Robin' Load balancer works in Datapower. The situation we have is that we have 10 backend servers and datapower forwards the request to each backend server in 'Round Robin' fashion ( configured via load balancer ). Now the question we have is, What if one server is responding slow ? Will data power loadbalancer wait till one request is complete, before it moves the request to the next available server ?

Example:
Step 1. Datapower sends a request to server 1
Step 2. Datapower sends a request to server 2
Step 3. Datapower sends a request, but server 3 is slow .... it waits for the response
Step 4. Datapower gets a response for server 4, forwards the next request to server 4

Now in step 4, Would DP wait for server 3 to respond or would send the request to server 4 even if there is no response from server 3.

I've looked into the documentation etc, but unable to confirm this behaviour.

Thanks in advance.

Gaurav
Updated on 2013-03-19T18:09:04Z at 2013-03-19T18:09:04Z by SystemAdmin
  • HermannSW
    HermannSW
    4501 Posts
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    Re: Datapower Round Robin

    ‏2012-12-10T08:31:07Z  in response to SystemAdmin
    Hi,

    DataPower can handle 1000s (sometimes 10000s) concurrent transactions.
    This can only be done if the LoadBalancer does not wait for a previous transaction to complete ...

     
    Hermann<myXsltBlog/> <myXsltTweets/>
    • PullMeOut
      PullMeOut
      47 Posts
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      Re: Datapower Round Robin

      ‏2012-12-10T16:02:19Z  in response to HermannSW
      Hermann

      Is there any limit on the number of concurrent transactions handled by datapower .As per most of the documnetation , i see there is no limit .

      But if i want to limit my number of concurrent transcations within datapower , how ?
      • HermannSW
        HermannSW
        4501 Posts
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        Re: Datapower Round Robin

        ‏2012-12-10T18:11:27Z  in response to PullMeOut
        >
        > But if i want to limit my number of concurrent transcations within datapower , how ?
        >
        this is done by SLM (Service Level Monitoring) in DataPower, see chapter 3 in this Redbook:
        http://www.redbooks.ibm.com/abstracts/redp4366.html

         
        Hermann<myXsltBlog/> <myXsltTweets/>
        • SystemAdmin
          SystemAdmin
          6772 Posts
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          Re: Datapower Round Robin

          ‏2013-03-19T10:29:04Z  in response to HermannSW
          Thanks for you reply HermannSW, how do we confirm that DP ( LoadBalancer ) is not waiting for transactions to complete. Currently we have DP LoadBalancer configured with round-robin and there is no SLM policy created. What we observe is 4 out of 5 backends are getting equal requests however 1 of the backends is getting lesser number of requests for DP

          What we suspect is, DP round robin algorithm is sending lesser requests to the system which is responding slowly however since round robin is involved we should get equal number of requests in all 5 backends.
          • SystemAdmin
            SystemAdmin
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            Re: Datapower Round Robin

            ‏2013-03-19T18:09:04Z  in response to SystemAdmin
            Are you doing health check on the servers? if so that server could have been unavailable and that will explain why it receives fewer connections.
            • SriHarshaVardhan
              SriHarshaVardhan
              7 Posts
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              Re: Datapower Round Robin

              ‏2013-07-06T20:06:04Z  in response to SystemAdmin

              Hi,

              even i have same problem..when i enable health check all memebers in LB are showing down status even though backends are up cound you please guide me enabling Helathcheck? ouk backend is WAS & health check is happening on port 80 by sending soap request.

               

               

              • HermannSW
                HermannSW
                4501 Posts
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                Re: Datapower Round Robin

                ‏2013-07-07T11:14:00Z  in response to SriHarshaVardhan

                Hi,

                please do a TCP Connection test from your DataPower box
                (Control Panel-->Trouble Shooting, with same settings for was backend, and port 80).

                If TCP connection test is not successful, you need to investigate the cause (missing DNS server, some firewall blocking, ...).

                In case TCP connection test is successful, then you might take a packet capture and verify by
                eg. Wireshark, whether the Health check requests are sent by DataPower, whether WAS sends returns, ...


                Hermann<myXsltBlog/> <myXsltTweets/> <myCE/>