Design Patterns for Rapid Development

In this section, you will learn how to implement some common functional design patterns. As you have learned, one of the advantages to using Connext DDS is that you can achieve significantly different functionality without changing your application code simply by updating the XML-based Quality of Service (QoS) parameters.

In this section, we will look at a simple newspaper example to illustrate these design patterns. Newspaper distribution has long been a canonical example of publish-subscribe communication, because it provides a simple metaphor for real-world problems in a variety of industries.

A radar tracking system and a market data distribution system share many features with the news subscriptions we are all familiar with: many-to-many publish-subscribe communication with certain quality-of-service requirements.

In a newspaper scenario (provided in an example called news example for all languages, a news publishing application distributes articles from a variety of news outlets—CNN, Bloomberg, etc.—on a periodic basis. However, the period differs from outlet to outlet. One or more news subscribers poll for available articles, also on a periodic basis, and print out their contents. Once published, articles remain available for a period of time, during which subscribing applications can repeatedly access them if they wish. After that time has elapsed, the middleware will automatically expire them from its internal cache.

This section describes Building and Running the News Examples and includes the following design patterns:

• Subscribing Only to Relevant Data
• Accessing Historical Data when Joining the Network
• Caching Data Within the Middleware
• Receiving Notifications When Data Delivery Is Late

You can find more examples at http://www.rti.com/examples. This page contains example code snippets on how to use individual features, examples illustrating specific use cases, as well as performance test examples.

© 2015 RTI