Java Reference
In-Depth Information
Chapter 13. Quality of Service
Introduction
“Quality of Service” is a general term that refers to a number of topics in different fields
within computing. For web services, it means simply the set of supporting infrastructure that
enhances the reliability, security, performance, and overall ability of your system to do its job
in accordance with its contract. In web services, these ideas are supported by a set of specific-
ations that complement each other and rely on each other to support message reliability and
delivery guarantees, metadata, transactions, and security.
These concepts are likely familiar to you through EJB. Indeed, this list is very similar to the
enhancements that a container provides around an EJB to make it operate as a full-blown com-
ponent.
While there are more than 100 WS-* specifications, they are not all used, and some are
more central to our work than others. This chapter will examine a small set of specifications
that address quality-of-service issues, including those for transactions, reliability, and policy
metadata. Given the breadth and scope of these specifications, and the wide array of vendors
that incorporate them into their products, it would be impossible to cover everything about
these specifications in one chapter, or even one book. Here I attempt to hit some of the primary
use cases you'll encounter.
Quality-of-Service Specifications
The web service features that we examine in this chapter are reliability, transactions, and
metadata. These are expressed in the specifications discussed in the following sections.
Reliability
The two specifications surrounding message reliability and delivery guarantee mechanisms
are WS-ReliableMessaging and WS-ReliableMessaging Policy.
WS-ReliableMessaging defines a messaging protocol to identify, track, and manage the re-
liable message delivery between two parties, termed a source and a destination. Apache
Sandesha is one open source project that implements this specification. It is also implemented
in .NET WCF, Glassfish, and WebLogic 10gR3.
WS-ReliableMessaging Policy enables a web service endpoint to indicate that a reliable mes-
sage delivery is required.
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