Topic
4 replies Latest Post - ‏2013-07-09T16:59:43Z by swlinn
SriHarshaVardhan
SriHarshaVardhan
7 Posts
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Pinned topic Load Balancer Status

‏2013-06-23T09:00:41Z |

I have a Load balancer object  with 3 members (WAS Servers). I enabled health check option in lb with default settings.  Even though the members are up.lb status option showing all the members as down. And unable to process any transaction coming to the proxy.

could any one help me in understanding how to configure health check for lb. Do i need to change health check port & any other customization is required.

 

  • Rohit-Goyal
    Rohit-Goyal
    104 Posts
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    Re: Load Balancer Status

    ‏2013-06-23T09:48:07Z  in response to SriHarshaVardhan

    You have to make sure that backends responding for health check calls coming from DataPower. 

    Rohit

  • swlinn
    swlinn
    1330 Posts
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    Re: Load Balancer Status

    ‏2013-06-26T02:35:38Z  in response to SriHarshaVardhan

    Assuming you're using a "Standard" type health check, the health ports on the member are used, and if not specified, the health port on the health page is then used.  You have two options, one SOAP which will send a SOAP request to your backend, the other a HTTP GET request.  In either case, you should have an XPath to validate if you get a response.  A / will be sufficient to just say you got an XML response.  As Rohit indicates, your backend url that you specify will get this request, and must respond with an XML response.

    Regards,

    Steve

    • SriHarshaVardhan
      SriHarshaVardhan
      7 Posts
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      Re: Load Balancer Status

      ‏2013-07-03T18:12:05Z  in response to swlinn

      Hi Steve,

      This is my observation :

      Case 1: Disabled Health Check  toggle in health check tab,.

                     We make one was instance down (say for A instance)

                     Statrted hitting proxy ; we noticed that A instance went into soft down status and requests are 

      routed to b,c instances. we are good with this behaviour.

       

      Case 2: Enables health check toggle in healthcheck tab.

      with in 2 minutes are servers went down even though all the servers are up.

      we are using default healthcheck settings. even health check port also we did not change. No heath check port is configured in members tab..its blank.

       

      please let me know do we need any customization to settings when we enable health check.?

      even though i disabled health check ; servers are going to soft down state when ever servers are down..this behaviour is fuling my requirement. tahnk what is the need of enabling health check ?

       

       

       

      • swlinn
        swlinn
        1330 Posts
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        Re: Load Balancer Status

        ‏2013-07-09T16:59:43Z  in response to SriHarshaVardhan

        Sorry for the lag in responding as I was on vacation last week and am catching up. 

        Case 1.  Since the one member is really down, the LBG will attempt to connect to it, but when it fails, it goes into a "quarantined" state as specified by the softdown state.  The LBG will not attempt this member again until the damp interval, by default 2 minutes, has expired.  You may see a delay every two minutes when that one member is retried, but after failing again it will go back into softdown state.

        Case 2.  So the health check is failing which is why the members go into a down state.  Perhaps you could provide an export of your LBG object as determining why the health checks are failing will depend upon your configuration and what your backend supports.  You mention you don't have a health port, so the port on the health page will be used for health check requests.  Is this port active on these servers to respond with an appropriate XML response?  The health check type, whether soap requests are to be sent (vs a HTTP GET) and the specific URI of that request will determine what health check is sent, and the xpath will determine if the XML response is accepted as valid.

        The reason for health checks is to not attempt to send traffic to backend members that are down to avoid any latency caused by waiting for the connection to fail.  It is a more proactive step to periodically determine if the backend is accepting requests.  Also, the health check frequency is generally less than the two minute damp time, so if the server comes back up you'll have that server back in service quicker.

        Regards,

        Steve