Dealing with Unpredictability

You have seen how web applications are now vastly more complex than just serving an HTML page to a browser. Some of the trends in modern web applications include

• Many different types of device can connect to a web application.

• Devices can act as inputs and outputs.

• Applications have different servers for different services within an application.

• Applications interact heavily with many third-party data sources.

• Real-time two-way data flow between clients and servers.

All these trends point to concurrency, which is a well-known and difficult problem in computing. Concurrency is a term to describe things that happen at the same time and can potentially interact with each other. A great example of a use case for Node.js is ql.io, a service created by eBay to provide developers with a single interface into multiple eBay data sources. This service makes it easy to request data from across the eBay organization. The service was created using Node.js and Subbu Allamaraju, Principal Member of Technical Staff, noted that the choice of using Node.js liberated them from some issues traditionally associated with concurrency.