In a previous article ("SOA - Ready for Primetime: The Next-Generation,
Grid-Enabled Service-Oriented Architecture") the authors discussed
how SOA grids can be used to break the convention of stateless-only
services for scalability and high availability (HA) by allowing stateful
conversations to occur across multiple service requests, whether between
disparate service boundaries or load-balanced groups of cloned service
instances. The SOA grid is a new approach to thinking about SOA
infrastructure. It provides state-aware, continuous availability for
service implementations, data, and processing logic. It's based on
architecture that combines horizontally scalable, database-independent,
middle-tier data caching with intelligent parallelization and an affinity
of business logic with cache data. This enables newer, simpler, and
more-efficient models for highly scalable service-oriented applications
that can take full advantage of service virtualization and event-driven
architectures. In this article they challenge traditional applications
of message-oriented middleware (MOM) for achieving high levels of quality
of service (QoS) when sharing data between services in an enterprise
service bus (ESB). They further compare and contrast a state-based,
in-memory storage and notification model, and investigate the intelligent
co-location of processing logic with or near its grid data in large
payload scenarios. Finally, they also explain when to substitute an
SOA Grid for existing MOM technologies as driven by the following
question: "If you have an SOA grid that can reliably hold application
state data and the necessary systems can access it, why continue to
utilize conventional messaging?" [...] An SOA grid transparently solves
many of the difficult problems related to achieving high availability,
reliability, scalability, and performance in a distributed environment.
Service-oriented architectures can fully leverage such a grid to
establish a QoS infrastructure far beyond the typical distributed
service integration currently delivered by conventional SOA techniques.
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