The demand for ever more sophisticated user interfaces in Web applications means that the skill set of the developers for these applications is not just server side scripting in languages such as Python or development in Java for example. Developers must also be expert in client side development in JavaScript to write code to interact with the server side code asynchronously. This model of development is a pull data approach where the client code has to pull data from the server. In those applications whereby the data on the server is only needed on the client if the data has changed, the client typically polls the server periodically, pulling the data and then checking to see if it has changed. Such an approach is not ideal for many reasons. Firstly, unnecessary work is being placed on both the client and the server, as undoubtedly requests will be made when there are no changes to the data. Secondly, changes in server side data will not be detected by the client until the next pull of data, meaning that if the frequency of checking is not high, the user interface will display stale data and may even miss some data changes.
The above problem occurs because HTTP is a stateless protocol with every request potentially on a new network connection. To solve the above problem, those using the Google App Engine (GAE) can make use of a new library known as the Channel API. This API allows a persistent connection to be made between a browser based application client and the server side code running on GAE servers. This solution comprises of server side libraries in Java and Python as well as a JavaScript library for the client side code. The Channel API allows the server side code to ‘push’ data changes to the client side code as and when needed.
The Channel API released by Google is an example of the innovation of the major Cloud vendors, providing Cloud based solutions to long existing problems in a clean lightweight manner. If you require a push data Web application, this API is definitely worthy of consideration. For more details, take a look here. If you would like to know more in general about the Google App Engine and how it compares to other Cloud Computing products such as Azure and Amazon AWS, why not consider attending the Learning Tree Cloud Computing course.
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