User Guide Rational Rose RealTime Connexis

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User Guide Rational Rose RealTime Connexis

Rational Software Corporation

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User Guide

RATIONAL ROSE® REALTIME CONNEXIS

VERSION: 2002.05.00

PART NUMBER: 800-025101-000

WINDOWS/UNIX

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Part Number: 800-025101-000

Version Number: 2002.05.00

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User Guide - Rational Rose RealTime Connexis v

Contents

Preface i

Road Map ii

See also “duplex locator service.”

SPP Service Provisioning Point. Term used to describe an

unwired port that is participating in a connection as the

publisher. The SPP acronym appears in portions of the

Run-time Service Library’s API.

tagged-values Term used to represent the parameters that are being

passed to the Connection Service when registering an

unwired port.

Target RSL Target Run-time System Libraries. These are the libraries

that are compiled into a Rose RealTime model and that

implement the messaging, state walking, and timing

service (among other services) of a Rose RealTime model.

TCP/IP Transmission Control Protocol / Internet Protocol.

Connection-based transport protocol.

Transport The underlying protocol that is being used to pass data

between communicating objects.

Table 1 Definitions

Term Definition

Connexis Application Layers

User Guide - Rational Rose RealTime Connexis 13

Connexis Application Layers

Connexis allows multiple Rose RealTime-generated executables to be

connected in a robust and reliable manner. Executables are networked

by connecting unwired ports across processor boundaries.

The Connexis programming model provides significant value:

■built for real-time - automatic mapping of UML communication

ports onto a high-performance software backplane

■product-ready, but flexible - the software is ready to run as soon as

it has been installed but can be adapted to handle project-specific

requirements

Transport

Integration

Framework (TIF)

A framework that lets 3rd parties (including developers)

add additional transports for use in Connexis Messaging.

UDP User Datagram Protocol. Connectionless transport

protocol.

UML Unified Modeling Language. An industry-standard

modeling language used to model object-oriented software

systems. UML is used by Rose RealTime and Connexis to

model the software that is being built.

unwired port An unwired port is a UML object that can have

connections specified using registration names. These

names can be specified at either design time or run-time.

virtual circuit A virtual circuit is the term used to refer to a connection

that has been established between two endpoints. This

refers to a connection between a single subscriber and a

single publisher.

wired port A wired port is a UML object that can have an explicit

connection (to another wired port) specified at design

time. The connection will be established at system

initialization time or at run-time if the port is contained in

a capsule that is optional or plug-in.

Table 1 Definitions

Term Definition

Chapter 1 Rational Connexis Overview

14 User Guide - Rational Rose RealTime Connexis

■simple-to-use programming model - supports client/server type

name binding and asynchronous messaging

■support for fault tolerance - detects failures and provides a

framework for dealing with faults

A Rose RealTime application that is using Connexis to implement its

inter-process communication has the high-level architecture shown in

Figure 2. The control paths that are shown, indicate the components

that are involved in registering and deregistering endpoints in the UML

application. All data that is sent between endpoints in a Connexis-

enabled application goes through the Transport component.

Figure 2 High level view of a Connexis enabled application

UML Application

This section presents an overview of how Connexis is used from within

Rose RealTime. For more information on Rose RealTime refer to the

“Rational Rose RealTime Toolset Guide.”

Ports in Rose RealTime

In Rose RealTime, ports are used to send messages between the

capsules in your model. Rose RealTime has several different kinds of

ports. The most common type of port is a wired port as shown in

Figure 3. Wired ports are visibly connected to other wired ports in Rose

RealTime models. Wired ports are represented graphically with two

connected squares in the oval part of the port icon.

Connexis Application Layers

User Guide - Rational Rose RealTime Connexis 15

Figure 3 Connecting wired ports

Another type of port that can be used in Rose RealTime is the unwired

port. Unwired ports are the primary method for establishing Connexis

connections. Once you have created an unwired port, you can specify

the connection service, protocol, and endpoint address that it will use

by registering the port with the Target RSL. This registration can either

be done automatically or through application code. The Connection

Service box in Figure 4 corresponds to the Distributed Connection

Service box in Figure 2. The DCS is one implementation of a

Connection Service.

Figure 4 Connecting unwired ports

A more detailed discussion on the registration process is provided in

“Establishing Connections” on page 107.

Chapter 1 Rational Connexis Overview

16 User Guide - Rational Rose RealTime Connexis

Distributed Connection Service

The Distributed Connection Service (DCS) is the connection service

that is provided with Connexis. It is responsible for maintaining

information about the unwired ports that have been registered with it

by a UML model. The DCS is the part of the system that is responsible

for establishing connections between unwired ports. It does this by

parsing the registration strings that are passed in when an unwired

port registers with the Target RSL.

Transport

The Transport is the component that is responsible for sending and

receiving data between processes. It manages any incoming or

outgoing data buffers and encodes and decodes data. A more detailed

break-down of the Transport component is shown in Figure 5.

Figure 5 Inside the Transport component

Connexis Application Layers

User Guide - Rational Rose RealTime Connexis 17

Locator Service

Another key component of a robust distributed system is a fault-

tolerant name service. A name service is used to find the actual

location of a server given a predetermined service name. A well-known

example of a name service is the Domain Naming Service (DNS) that is

widely used on the Internet. The principle function of a name service is

to look up a specific address when it is given a service name. This

isolates the calling application from changes in the physical addressing

of network components. In the Connexis product, the Locator Service

provides the name service functionality.

The Locator Service actually does a bit more than just operate as a

name server. The Locator can be configured to arbitrate between more

than one endpoint that provides the same service and it can also be set

up to run in duplex mode, which allows a backup Locator to

automatically take over when the primary fails.

Using the locator

An endpoint is defined to be the combination of a transport protocol

and the address of a specific port in a distributed application. For

example, cdm://address:port. If an explicit endpoint is provided, then

the client will try to connect to the server at the specified endpoint. If a

complete endpoint is not provided then the Locator is contacted. The

Locator returns an endpoint that is then used by Connexis to choose

the appropriate service provider or peer. The service name by which an

endpoint is referred, is specified as part of the registration of that

endpoint.

The Connexis Locator Service supports both a primary and a backup

locator. In this way, a distributed application can be made more robust

by ensuring that there is no single point of failure in the name server.

Chapter 1 Rational Connexis Overview

18 User Guide - Rational Rose RealTime Connexis

The HelloWorld Model

The HelloWorld model implements a simple distributed model using

Connexis. The model demonstrates the use of the Connexis Locator

Service and how it can be used to easily provide backup service in a

distributed environment.

The model contains two servers, a client, and the Connexis locator

service, each running independently. The servers speak different

languages (either English, or French). Initially, the client is bound to

the server that comes up first. Once bound, the client makes requests

to the server and the server sends back a greeting in the language it

speaks.

If the server to which the client is bound becomes unavailable, the

client is notified of the connection loss, and it rebinds to the backup

server, which starts responding to the client requests in the language

it speaks. For example, if the client is initially bound to the English

server, it will start receiving greetings in English. If you then terminate

the English server (for example, resetting through the RTS panel), the

connection will be lost momentarily, the client will be rebound to the

French server, and the client will start receiving the greetings in

French.

Note: The greetings are output to the DOS window (Windows) and the

RTS Output window (Solaris), which comes up when the client is started.

Running the HelloWorld Model

The model can be run on all supported host platforms. To run the

application, start up the matching (for example, VC++6.0) set of

locator, client, EnglishServer and FrenchServer component instances.

■Keep the DOS (Windows) or RTS Output (Solaris) window for the

client in view. The other DOS or RTS Output windows can be

minimized to reduce screen clutter.

■Run all the component instances from the corresponding RTS

panels.

The HelloWorld Model

User Guide - Rational Rose RealTime Connexis 19

■If you run the EnglishServer first, you should see “Hello World!!!”

appear on the client DOS window repeatedly. At this point, you can

terminate the EnglishServer instance by means of the RTS panel.

The client will receive a connection loss, and will then switch over

to the FrenchServer as soon it is rebound via the locator service.

You should now start to see "Salut le monde!!!" displayed in the

client DOS window.

Additional HelloWorld Models

The following models are extensions of the HelloWorld model. They

provide examples of distributed load-sharing and fault-tolerant

patterns.

HelloWorldHotStandby

A client connects to two servers through a proxy actor, and continually

sends greeting requests. The proxy forwards the message to both

servers, and both of the servers respond back to the proxy, which in

turn relays the message from the active server to the client. If there is

no response from the active server within a specified time period, the

other server becomes active, and starts to handle all the client

requests.

HelloWorldLoadSharing

This model consists of two servers (an English and a French one) that

supply greeting messages for multiple clients. The clients connect to

the servers in a round-robin fashion. For example, if you had four

clients, the first and the third client would connect to one server and

the second and the fourth client would connect to the other server.

HelloWorldOverflowToBackupService

This model contains two servers (an English and a French one). One of

the servers is given a higher rank so that it acts as the primary server.

The clients connect to the primary server until the primary server has

reached its full capacity. Any subsequent clients will connect to the

backup server, which will handle their greeting requests for those

clients.

Chapter 1 Rational Connexis Overview

20 User Guide - Rational Rose RealTime Connexis

HelloWorldRedundantLocator

The model consists of one server, multiple clients, and a primary and

a backup locator. The clients connect to the server using the primary

locator. The server, in turn, provides greeting signals for the clients. If

the primary locator is shut down, all subsequent client-server

connections will be established using the backup locator.

Using Connexis

There are several steps that must be taken to add Connexis support to

a model. These are:

■share the RTDInterface package

■add Connexis component capsule roles to appropriate capsules in

the model

■integrate transport protocols

■configure components for your application

Note: The Connexis configuration dialogs on ports and capsules

allow the user to perform these steps as well.

In addition to these steps, there are also general design rules that must

be followed to ensure that the Connexis components have been

initialized properly before they are used.

Refer to “Adding Connexis Support to Your Model” on page 83 for more

information on Connexis-enabling your application.

User Guide - Rational Rose RealTime Connexis 21

Chapter 2

Using Connexis Model Examples

With Connexis, four model examples are included to accelerate your

learning and proficiency. The list of models are outlined below:

■The BasicTest Model can be used to verify your environment.

■The Quick start Model runs you through an introductory tutorial.

■The HelloWorld Model presents a simple distributed model.

■The Performance Model lets you evaluate the performance of

Connexis-enabled models in your environment.

By default, components in these model examples specify ‘localhost’

(127.0.0.1) as the host machine. If you want to run the model examples

remotely (that is, on a specific processor rather than the one you are

on), you must modify the model examples first.

The BasicTest Model

The BasicTest model implements a very simple client server distributed

system and is intended for use as a simple model to test proper

Connexis installation and operation on any of the Connexis-supported

platforms.

All hosts and target configurations supported with your Connexis

installation are provided.

To run the model on one of the supported configurations listed above,

see “Verifying your installation using BasicTest, in the Release Notes

and Installation Guide for Rational Rose RealTime Professional.

Chapter 2 Using Connexis Model Examples

22 User Guide - Rational Rose RealTime Connexis

The Quick Start Model

The “Rational Connexis User Guide” provides a Quick start tutorial

(chapter 2) to allow you to quickly come up to speed on using Connexis.

The tutorial is composed of three iterations. Iteration 1 takes you

through building a simple ping pong model using Rose RealTime.

Iteration 2 takes you through the steps required to Connexis-enable

the ping pong model and make it distributed.

For your reference, complete, documented models for each iteration

are provided as part of the model examples provided with Connexis.

These examples can be run on all supported host platforms. For

detailed instructions on using the Quick Start model, see “Quick Start”

on page 31.

Quick Start Iteration 1 Model

The PingPong_Iteration1 model is the completed version of the model

developed in Connexis Quick start tutorial (Iteration 1). See “Quick

Start” on page 31 for details.

This model implements a simple ping pong application using Rose

RealTime. This model is used as a starting point for

PingPong_Iteration2 to show the simple steps required to quickly

Connexis-enable an application built using Rose RealTime.

To run the model, compile the PingPongApp component instance

corresponding to your host compiler, and choose run from the item

menu of the component instance under the PingPongProcessor.

Quick Start Iteration 2 Model

The PingPong_Iteration2 model is the completed version of the model

developed in Connexis Quick start tutorial (Iteration 2). See “Quick

Start” on page 31 for details.

This model implements a simple distributed ping pong application

using Rose RealTime and Connexis. It is a Connexis-enabled version of

the model developed in Iteration 1, and demonstrates the simplicity of

distribution using Connexis.

The HelloWorld Model

User Guide - Rational Rose RealTime Connexis 23

To run the model, please compile the Ping and Pong component

instances corresponding to your host compiler, and choose run from

the item menu of the component instances under the

PingPongProcessor.