Exalogic Software Optimisations

[Update 19-March-2001 - this blog entry is actually a short summary of a much more detailed Oracle internal document I wrote in December 2010. A public whitepaper using the content from my internal document, has now been published on Oracle's Exalogic home page (see "White Papers" tab on right-hand side of the home page); for the public version, a revised introduction, summary and set of diagrams have been contributed by Oracle's Exalogic Product Managers.]

For version 1.0 of Exalogic there is a number of Exalogic-specific enhancements and optimisations that have been made to the Oracle Application Grid middleware products, specifically:

• the WebLogic application server product;
• the JRockit Java Virtual Machine (JVM) product;
• the Coherence in-memory clustered data-grid product.

In many cases, these product enhancements address performance limitations that are not present on general purpose hardware that uses Ethernet based networking. Typically, these limitations are only manifested when running on Exalogic's high-density computing nodes with InfiniBand's fast-networking infrastructure. Most of these enhancements are designed to enable the benefits of the high-end hardware components, that are unique to Exalogic, to be utilised to the full. This results in a well balanced hardware/software system.

I find it useful to categorise the optimisations in the following way:

1. Increased server scalability, throughput and responsiveness. Improvements to the networking, request handling, memory and thread management mechanisms, within WebLogic and JRockit, enable the products to scale better on the high-multi-core compute nodes that are connected to the fast InfiniBand fabric. WebLogic will use Java NIO based non-blocking server socket handlers (muxers) for more efficient request processing, multi-core aware thread pools and shared byte buffers to reduce data copies between sub-system layers. Coherence also includes changes to ensure more optimal network bandwidth usage when using InfiniBand networking.
2. Superior server session replication performance. WebLogic's In-Memory HTTP Session Replication mechanism is improved to utilise the large InfiniBand bandwidth available between clustered servers. A WebLogic server replicates more of the session data in parallel, over the network to a second server, using parallel socket connections (parallel "RJVMs") instead of just a single connection. WebLogic also avoids a lot of the unnecessary processing that usually takes place on the server receiving session replicas, by using "lazy de-serialisation". With the help of the underlying JRockit JVM, WebLogic skips the host node's TCP/IP stack, and uses InfiniBand's faster “native” networking protocol, called SDP, to enable the session payloads to be sent over the network with lower latency. As a result, for stateful web applications requiring high availability, end-user requests are responded to far quicker.
3. Tighter Oracle RAC integration for faster and more reliable database interaction. For Exalogic, WebLogic includes a new component called “Active Gridlink for RAC” that provides application server connectivity to Oracle RAC clustered databases. This supersedes the existing WebLogic capability for Oracle RAC connectivity, commonly referred to as “Multi-Data-Sources”. Active Gridlink provides intelligent Runtime Connection Load-Balancing (RCLB) across RAC nodes based on the current workload of each RAC node, by subscribing to the database's Fast Application Notification (FAN) events using Oracle Notification Services (ONS). Active Gridlink uses Fast Connection Failover (FCF) to enable rapid RAC node failure detection for greater application resilience (using ONS events as an input). Active GridLink also allows more transparent RAC node location management with support for SCAN and uses RAC node affinity for handling global (XA) transactions more optimally. Consequently, enterprise Java applications involving intensive database work, achieve a higher level of availability with better throughput and more consistent response times.
4. Reduced Exalogic to Exadata response times. When an Exalogic system is connected directly to an Exadata system (using the built-in Infiniband switches and cabling), WebLogic is able to use InfiniBand's faster “native” networking protocol, SDP, for JDBC interaction with the Oracle RAC database on Exadata. This incorporates enhancements to JRockit and the Oracle Thin JDBC driver in addition to WebLogic. With this optimisation, an enterprise Java application that interacts with Exadata, is able to respond to client requests quicker, especially where large JDBC result sets need to be passed back from Exadata to Exalogic.

To summarise, Exalogic provides a high performance, highly redundant hardware platform for any type of middleware application. If the middleware application happens to be running on Oracle's Application Grid software, further significant performance gains will be achieved.

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