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Sunday, May 17, 2009

In-Depth: Load-Balancing E-Business Suite Environments

As I watched blood drain from my arm, my thoughts turned to load-balancing and system redundancy. My phlebotomist had just cheerfully informed me the lab's primary testing PC had failed that morning, so there would be an unusual delay in getting blood test results until a replacement arrived.


Increasing Fault Tolerance at Lower Cost

You can use load-balancing routers (LBRs) to protect your E-Business Suite from similar types of system failures. Load-balancers increase your environment's fault-tolerance and scalability by distributing load across a pool of application servers like this:

Generic Apps Load-balancing:

Besides fault-tolerance and scalability, another appealing benefit is that you can use load-balancing to substitute expensive SMP boxes with clusters of inexpensive Linux-based commodity servers.

Linux Load-Balancing on Oracle's Global Single Instance

In fact, this is what we've done at Oracle: our own E-Business Suite environment is a Global Single Instance running on about 58 Linux-based application servers. This has reportedly saved us millions in operating costs.

If you're joining us at this year's OpenWorld conference, make sure you attend Bret Fuller's ever-popular session on how we run the E-Business Suite internally; some of the statistics he shows on our transactional volumes are mind-blowing.

Supported Load-Balancing Methods

The E-Business Suite supports the following types of load-balancing:
I'll cover only the first two methods in this article.

HTTP Layer Load-Balancing

HTTP Layer load-balancing is the most common method used in E-Business Suite environments.

HTTP Layer Load-Balancing:

In this configuration, end-users navigate to a specific Web Entry Point that represents your E-Business Suite's domain name. An HTTP Layer load-balancer routes all subsequent traffic for a specific user to a specific Web Node.

HTTP Layer load-balancers may use heartbeat checks for node death detection and restart, and sophisticated algorithms for load-balancing.

DNS-Based Load-Balancing

When an end-user's browser attempts to access your E-Business Suite environment, your local Domain Name Server (DNS) can direct that user to a specific application server in a pool based on available capacity:

DNS-Based Load-balancing:

Traffic for that user's session will be handled by the application server 10.10.10.10, while other users' traffic may be directed to other application servers in the pool. Like HTTP layer load-balancers, many DNS-based load-balancers use heartbeat checks against nodes and sophisticated algorithms for load-balancing.

Business Continuity ("Disaster Recovery")

Our larger enterprise-class customers combine DNS-based and HTTP layer load-balancers to support their business continuity plans. In the event of a disaster, end-users are directed via a DNS-based load-balancer from the primary E-Business Suite environment to an offsite standby site.

Disaster Recovery using DNS + HTTP LBRs:

Minimum Requirement: Session Persistence

Remember that although Oracle doesn't certify specific load-balancers or networking hardware with the E-Business Suite, we do support their use generically.
In other words, we've designed the E-Business Suite to be able to use load-balancers in general.

The minimum requirement is that a load-balancer support session
persistence
, where a client's initial HTTP connection is directed to a
particular application server, then subsequent HTTP requests from that
client are directed to the same server. As long as a
load-balancer is able to handle session persistence (also referred to
as "stickiness"), it's likely to work with the E-Business Suite.

Happy Learning !

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