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dbeavon
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I'm looking for clarification about an article in the documentation for PASOE. This is one of the options that is available for load-balancing. Amazon Elastic Load Balancer (ELB): OpenEdge 11.7 Documentation Has anyone had any success with this load balancer in production? I don't have access to the Amazon ELB but we have another load balancer, called Citrix Netscaler, and I think it can serve a similar purpose. I am particularly interested in that load-balancing strategy. It is described as using a "proprietary cookie" (AWS_ELB). In order for this strategy to work, does PASOE need to be configured in any special way? The documentation does NOT say anything about what needs to happen on the PASOE side of things for the load-balancer to be able to work properly. I'm guessing that the PASOE applications need to be configured to use HTTP sessions provided by tomcat. Is there anything else? On a conceptual level, do the PASOE instances even know that the AWS ELB is sitting out in front? Or are they totally unaware of that detail? I'd also like to understand how the load-balancing strategy works. I think it injects its own cookie into the HTTP headers that are sent back and forth to tomcat. It then uses this cookie to determine how to redirect future HTTP traffic from the same client. I suspect that as long as the tomcat session hasn't timed out, then the load balancer will continue to send HTTP traffic to the same tomcat instance. So as long as the PASOE hasn't lost track of the session, then the load balancer should work properly, right? Please let me know if I have gotten anything wrong. In the case of citrix netscaler, there are a couple "persistence" strategies that the load-balancer uses. The one that we've used thus far is called "client IP persistence". It is straight-forward and easy to configure. All traffic from the same client machine is directed to a single tomcat instance. This is fine if there are lots of independent clients that do small amounts of work. But it is a problem if there is a really *big* client machine that runs batch processes, services, reports, and such. All the activity from that machine will be sent to a single pasoe instance and swamp it. The alternative is another "persistence" strategy based on HTTP cookies. I haven't had any experience with it yet, but I suspect it works in a way that is similar to the Amazon ELB. I'd appreciate any additional details about that type of load balancing before we start blindly experimenting with it. PS. Here is the info on the "persistence" strategy in citrix netscaler that uses HTTP cookies. HTTP cookie persistence
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