ZeroC ICE技术通讯第五期：深入IcePack与死锁避免

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"ICE 学报第五期，发布于2005年8月，包含多个专题，如：IcePack介绍、Ice-E预览、避免死锁（第二部分）以及常见问题解答（FAQ Corner）。" 在这期ICE学报中，我们关注的是分布式计算和通信的相关技术。首先，"Introduction to IcePack"章节将深入介绍IcePack，这是一个可能涉及ZeroC公司提供的软件包或框架，它可能用于支持分布式系统中的对象间通信和数据交换。IcePack可能包含了优化的网络协议、序列化机制以及其他提升效率和可扩展性的工具，对于理解和使用Ice生态系统的开发者来说，这部分内容是至关重要的。接下来，"Ice-E: A Preview"章节预告了Ice-E，这可能是一个新的扩展或特性，可能涉及到增强的性能、安全特性或者是对现有Ice平台的某种增强。这部分内容将为读者提供一个前瞻性的视角，了解即将推出的技术如何改进现有的分布式应用。在" Avoiding Deadlocks, Part II"中，继续了上一期关于死锁避免的讨论。死锁是多线程和分布式系统中的常见问题，这部分可能提供了更深入的策略和技术，帮助开发者识别和预防这类问题，确保系统的稳定性和高可用性。这部分内容可能包括了具体的编程实践、设计模式或者算法，对于避免在并发环境中遇到的复杂同步问题非常有帮助。 "FAQ Corner"通常会收集并解答社区中常见的问题，这部分可能会涵盖各种实际操作中的疑惑，例如配置问题、性能优化建议或者错误排查方法，为读者提供实用的解决方案和最佳实践。此外，学报还引发了一场关于RPC（远程过程调用）本质的讨论。RPC是分布式系统中的一种重要通信方式，不同观点认为SOAP是否可以被视为真正的RPC。文中提到了Michi的观点，他认为任何请求/响应系统都属于RPC范畴，而其他观点则强调在API层面上，只有具有本地过程调用相似“感觉”的请求/响应才算是RPC。由于SOAP可以与多种消息队列风格结合，有些人认为SOAP不完全符合RPC的传统定义。这部分讨论揭示了分布式通信中的理论和实际应用之间的差异，对于理解不同通信协议的适用场景非常有益。这期ICE学报涵盖了从基础工具到高级概念的广泛内容，是分布式系统开发人员和研究人员的重要参考资料。通过深入学习这些文章，读者可以增强对Ice平台的理解，掌握避免死锁的技巧，并对RPC有更深入的认识。

PAGE TITLE

Connections

ZeroC’s Newsletter for the Ice community

Page 4 Issue 5, August 2005 Page 5Issue 5, August 2005

Connections

ZeroC’s Newsletter for the Ice community

Connections

ZeroC’s Newsletter for the Ice community

Page 4 Issue 5, August 2005 Page 5Issue 5, August 2005

Connections

ZeroC’s Newsletter for the Ice community

Using IcePack, applications can locate objects in three ways.

1. Object identity

Given the object identity, the application queries IcePack and

locates the given object.

2. Object type

Given an object type-id, IcePack returns all objects that

implement this type.

3. Object identity @ adapter id

Given the object identity and an adapter id, the application

queries IcePack and locates the given object adapter.

Server Deployment

Deployment descriptors make your application very easy to man-

age: you describe a deployment once and deploy many times with

potentially different deployment scenarios, such as deployment for

a test suite and deployment for production. A deployment descrip-

tor is an XML ﬁle that describes the structure of your application.

Deployment of your application does the following:

• creates server conﬁguration ﬁles

• initializes any required Freeze database environments

• registers servers with the appropriate IcePack node daemon

• adds object adapters to the IcePack registry

• adds well-known objects and their identities to the IcePack

registry

Preparing the Chat Session Server

Strictly speaking, the server can be managed by IcePack as it is.

However, in order to fully take advantage of IcePack, we must

make a few changes. IcePack generates conﬁguration ﬁles from a

server’s deployment descriptor, so we must remove the hard-coded

conﬁguration ﬁle.

// C++

int

main(int argc, char* argv[])

{

ChatSessionServer app;

return app.main(argc, argv);

}

Since we want to use indirect binding, we can remove the IceStorm

TopicManager proxy from the conﬁguration ﬁle and instead look

up the object by identity. The code originally was:

// C++

string str = communicator->getProperties()

->getProperty("IceStorm.TopicManager.Proxy");

_manager = IceStorm::TopicManagerPrx::

checkedCast(communicator->stringToProxy(str));

The code now becomes:

// C++

_manager = IceStorm::TopicManagerPrx::

checkedCast(communicator->

stringToProxy("IceStorm/TopicManager"));

Under the covers this locates the object by identity using IcePack.

It is equivalent to the following code:

// C++

IcePack::QueryPtr query = IcePack::Query::

uncheckedCast(communicator->

stringToProxy("IcePack/Query"));

Identity id;

id.name = "IceStorm/TopicManager";

_manager = IceStorm::TopicManagerPrx::

checkedCast(query->findObjectById(id));

How does the application know how to locate the IcePack registry?

This is conﬁgured in the conﬁguration property Ice.Default.

Locator and is provided automatically by IcePack to any IcePack

managed servers.

These are all the changes that are nec-

essary to enable the chat server to be an

IcePack-managed server. Next we need

to write the deployment descriptor.

Deployment Descriptors

An IcePack deployment descriptor con-

tains a description of:

• nodes on which the servers are deployed

• servers that run on the nodes

• IceBox services that are hosted by a

server, if applicable

• object adapters, and well known objects

and their type hosted by the servers and

services

Figure 4: Indirect Binding

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INTRODUCTION TO ICEPACK

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ZeroC ICE技术通讯第五期：深入IcePack与死锁避免

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