Chapter 5. The ACE Service Configurator Framework

关于ACE的详细介绍,ACE是一种跨平台的网络编程框架

Ru-Brd

关于ACE的详细介绍,ACE是一种跨平台的网络编程框架

Service Configurator framework uses to

configure and control a service

implementation. Control operations

include initializing, suspending,

resuming, and terminating a service.

ACE_Service_Repository A central repository for all services

managed using the ACE Service

Configurator framework. It provides

methods for locating, reporting on, and

controlling all of an application's

configured services.

ACE_Service_Repository_Iterator A portable mechanism for iterating

through all the services in a repository.

ACE_Service_Config Provides an interpreter that parses and

executes scripts specifying which

services to (re)configure into an

application (e.g., by linking and

unlinking DLLs) and which services to

suspend and resume.

The most important relationships between the classes in the ACE Service

Configurator framework are shown in . These classes play the following roles in accordance with the Component Configurator pattern []:

Figure 5.1. The ACE Service Configurator Framework Classes

lConfiguration management layer classes perform application-independent strategies to install, initialize, control, and shut down service objects. The classes in the configuration management layer in the ACE

Service Configurator framework include ACE_Service_Config,

ACE_Service_Repository, and ACE_Service_Repository_Iterator. Application layer classes implement concrete services to perform an application's processing. In the ACE Service Configurator framework,

application layer classes are descendants of ACE_Service_Object, which

in turn inherits from ACE_Event_Handler (), thereby enabling

service objects to be linked and unlinked dynamically, and to participate in

the ACE Reactor framework. l

关于ACE的详细介绍,ACE是一种跨平台的网络编程框架

The ACE Service Configurator framework provides the following benefits:

lFlexibility. The framework allows developers to offer multiple services, and a choice of different implementations of services, that can be assembled at run time. The choices concerning which services to execute on which

network node(s) can be made (and changed) at any point, ranging from

application build time to the actual point when services start running.

Developers can also limit choices (e.g., by not offering dynamically linkable services) where desired.

Configurability. Developers can customize and configure application data for nearly any aspect of a service and for each deployment. Services can be developed to read traditional configuration data, such as port numbers,

network addresses, and file system locations. Moreover, services can allow

tuning and performance decisions to be deferred until the right information

is available to guide them. For example, depending on the run-time

platform's available multithreading facilities and available CPUs, it may be

either more or less efficient to run multiple services in separate threads or

separate processes. The ACE Service Configurator framework enables

applications to be configured by site-knowledgable administrators, or they

can select and tune these behaviors flexibly at run time, when there's

enough information to help match client demands with available system

processing resources.

Managability. All configuration information can be stored in a configuration script file, known as svc.conf. The framework uses these scripts to load

and configure services. An application's installation procedure can record

settings in an svc.conf file. Administrators can also edit and tune this

information as needed, without rebuilding the application itself. Applications can form their own configuration directives and pass them directly to the

ACE Service Configurator framework. The framework groups an application's services into one administrative unit and enables an application to report on its services and their states.

Consistency. The framework imposes a uniform interface for initializing, suspending, resuming, and terminating a service. This uniformity provides

consistency to framework users and allows services to be treated as building blocks that can be assembled flexibly to form complete applications.

Maintainability. The framework's decoupling of service implementation from configuration into networked applications allows service

implementations to evolve over time, independently of which networked

applications they're included in. Each service can be developed and tested

independently, which simplifies subsequent service composition and

increases reuse.

Enhanced dynamism and control. The framework enables a service to be reconfigured dynamically without modifying, recompiling, or statically relinking existing code. Each service can also be reconfigured without lllll

关于ACE的详细介绍,ACE是一种跨平台的网络编程框架

affecting other services or stopping and restarting the server process itself.

These reconfiguration capabilities are often required for high-availability

applications, such as mission-critical systems that perform online transaction processing or telecom call processing.

The remainder of this chapter motivates and describes the capabilities of each class in the ACE Service Configurator framework. We also illustrate how this framework can be used to enhance the extensibility of our networked logging server. If you aren't familiar with the Component Configurator pattern from

POSA2 we recommend that you read about it first before delving into the detailed examples in this chapter.

R …… 此处隐藏：24458字，全部文档内容请下载后查看。喜欢就下载吧 ……