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In a small Java Cluster which instance do you send requests to?

Former Member
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We have the Central Services and Central Instance running on one machine. Then a single Dialog instance on another. Does anyone know if there is any reason we would direct user requests to the Dialog instance and not the Central Services?

Thanks

Tom

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samuli_kaski
Active Participant
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To distribute load to both servers by a predefined rule or even dynamically?

Are you using something in front of the two SAP J2EE Engines? SAP Web dispatcher? Some other load balancing software or hardware?

The SAP J2EE Engine by default distributes load only locally (on the same physical server), it can however be configured to dispatch globally but that isn't recommended by SAP.

A pretty good starting point in understanding how the SAP J2EE dispatcher works would be to read SAP notes 772561 and 761514.

Former Member
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Thanks for those SAP Notes, they answered the questions which the documentation could not.

To answer your question, currently we have no other devices in front of the servers to balance load. A consultant was brought in before me and suggested to just direct all requests to the Dialog instance. I could not follow the logic based on all the documentation out there but I guess I do now. So basically if we want to balance load we will need a Web Dispatcher or some other device to direct connections to the instances.

Now I have but one more question. We are using Windows Integrated Authentication (IISProxy) in front of the portal. To balance load in this scenario we will have to place the web dispatcher in between the IISProxy and the portal right? Like this:

User<->IISProxy<->Web Dispatcher<--->Dialog Instances

Thanks Again!

samuli_kaski
Active Participant
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That's right. You could also have several IIS Proxy servers and place the Web dispatcher in front of them however in that scenario your need for additional hardware will increase. Please keep in mind that your IIS Proxy will become a SPOF (Single Point Of Failure) if done the way you have planned.