Ice Reading Notes-middleware concepts and ice Overview (1)

I. Middleware

1. Introduction

In short, middleware is an independent system software or a service application. Middleware is located on the operating system of the client and server, and is mainly responsible for network resource management and network communication. Middleware is a kind of software, not a kind of software. Middleware not only achieves interconnection, but also achieves interoperability between applications;Middleware is a distributed processing-based software. Its network communication function is the most prominent feature..

2. Features of Middleware

1) run inIn a Heterogeneous EnvironmentThat is to say, it can run in a variety of hardware and operating systems;

2) supportedDistributed ApplicationTo provide interaction between applications or services across networks or operating system platforms;

3) Some standard network protocols and interfaces are also supported;

3. Middleware Classification

1) remote process call: the server and client can be located on the same computer, different computers, or even running on different operating systems.

2) message-oriented middleware: Mom refers to the use of an efficient and reliable message transmission mechanism for platform-independent data exchange and integration of Distributed Systems Based on Data Communication. The program puts messages into the message queue or retrieves messages from the message queue for communication. All activities associated with the message queue, for example, it is a mom task to maintain message queues, maintain the relationship between programs and queues, process network restarts, and move messages in the network. programs do not directly communicate with other programs, and they do not involve the complexity of network communication.

3) The Object Request proxy (ORB) is an object bus, which is at the core of the CORBA specification. It defines the basic mechanism for objects to transparently send requests and receive responses in a heterogeneous environment, is the middleware that establishes the client/server relationship between objects.

4) Transaction Processing monitoring is performed between the client and server for transaction management and coordination, load balancing, and Failure Recovery to improve the overall performance of the system. It can be seen as the "Operating System" of the transaction processing application ".

 

II. Ice Overview

1. Ice Architecture

1.1) Overview

Ice is an object-oriented middleware platform. Ice applications are suitable for use in heterogeneous environments: customers and servers can use different programming languages

Language Programming can run on different operating systems and later-day machine architectures, and can use a variety of network technologies for communication.

1.2) Terms

1.2.1) Customer and server: the client at the end of the request and the server at the end of the application service.

1.2.2) Ice object

An ice object is a conceptual entity (or abstract ). Features of ice objects:

-- The ice object is an object that can respond to customer requests in a local or in-situ address space.

-- An ice object can be instantiated on one or more servers. If an object has multiple instances, it is still an ice object.

-- Each ice object can be instantiated on one or more servers.

-- An operation has zero or multiple parameters. And a return value.

-- Each ice object has a unique object ID.

1.2.3) proxy (proxies)

To contact an ice object, the customer must hold the proxy of the object. Proxy is a product in the customer's address space.

For the customer, the proxy is the representative of the ice object (this object may be in the same place)

When the customer calls an operation on the proxy, the ice run time will: locate the ice object ---> If the server of the ice object is not running, it will stimulate

Live him --> activate the ice object on the server --> wait for the Operation to complete --> return all out parameters and return values to the customer.

***String proxy: To contact an object, the customer only needs to know the identifier, addressing information, and object type of the object.

OK.

***Direct proxy: It stores the identifier of an object and the running address of its server. The address is completely composed of two items.

OK: Protocol identifier (such as TCP or UDP), specific Protocol address (such as host name and port number)

***Indirect proxy: Contains the identifier of an object and the Object Adapter name. However, the indirect proxy does not contain addressing information. Object

The adapter name is mapped to the Protocol-address pair.

1.2.4) servants

The customer request must arrive at the server and execute code within the server. The product that provides operation calls on the server is called

Servant. Actually. Servant is an instance of classes written by server developers.