Distributed computing is the new norm.


Multi-service architectures surround us daily. Our computing needs are served from many different independently operated services, and all implemented using different underlying technologies. When these independent units bring only one small service or set of services, it is called a microservice. While there is still some industry discussion about the exact properties of a microservice, one thing can be agreed upon: microservice-based systems enforce modular design by default. This begs the question, if my services are decoupled and modular, how do they communicate effectively to create an entire system that performs something useful?

Enterprise Service Buses and Middleware

The solution to this problem is a connector software which acts as a message routing bus. The Enterprise Service Bus (ESB), often simplified as Middleware (although Middleware is not always an ESB), allows these decoupled services to talk to each other in a language and medium-neutral way. For instance, if you have a Service-Oriented Architecture (SOA) comprised of services written in different languages, with a few plug ‘n play components, but they all need to share data, a language-neutral ESB is in order.

Many of the commercial ESBs are written as a publisher-subscriber (PubSub) system. This allows the individual services to subscribe to the types of messages it is interested in knowing about. The ESB or Middleware is responsible for managing the “channels” and relaying the published messages to the right subscribers. The Middleware or ESB provider will usually provide a connector for many languages making it easy to interface your services to the ESB. If the connector is not provided, the specification will usually be provided so that you can implement your own connector. This allows an SOA system to communicate without worrying about the transport mechanism of its messages.


It’s easy to see that ESBs can be found nearly everywhere in technology. In fact, many of the most common services we use today can be loosely classified as an ESB. Perhaps I’ll start a project soon to build an ESB and see how it goes?

Thanks for reading!