Understanding Middleware: What It Is and How It Works

Distributed systems are highly scalable and efficient — but only when integrated into a powerful network. A distributed system can only function if all its applications can communicate effectively with one another. However, this is often easier said than done due to the multi-layered nature of modern architectures.

Modern architectures consist of applications written in various languages with different protocols, and they are spread across multi-cloud and multi-cluster environments. With so many different components in question, middleware makes connectivity possible.

What is middleware?

At its simplest, middleware are pieces of software that live between two different components. Middleware is a contraction of the words ‘middle’ and ‘software’ — it is software in the middle.

The term middleware has been in use since at least 1968, when it was included in a report on a NATO Software Engineering conference that took place in Garmisch-Partenkirchen, Germany. At the time, middleware had a pretty straightforward use case: to exchange data between monolithic applications. Middleware took the form of massive software components that collected data from one application and deliver it to another. Today, we would call this an Extract Transform Load (ETL).

Contemporary information systems are much more heterogeneous, and middleware must take a much more active role. In addition to relaying traffic from one application to another, today’s middleware affects the messages themselves. This is because distributed systems require middleware to enable communication between two components not designed to communicate with one another.

Modern middleware offers the ability to transform data so the messages being relayed can be understood by the receiving application. Middleware also provides functions to secure the network, restricting access to unknown users. It can add or remove data from messages, to fulfill requirements or simplify the network. Finally, middleware can aggregate data from different applications. These are a few ways modern middleware lets you affect the messages passed along a network.

How does middleware work?

Modern middleware is a transformation layer that sits between two applications. The reverse proxy of one application transmits a message to the entrypoint of the middleware layer. The message then passes through a router before being sent through a chain of middleware that transforms, secures, adds to, or removes from the message. Finally, the message passes through the service of the middleware layer before going to the correct service of the receiving application.

What are some examples of middleware?

Modern middleware often include a rich list of features.

Middleware transforms messages by:

• Translating data from one protocol to another
• Compressing data
• Removing unnecessary information, such as prefixes

Middleware secures the network by:

• Authorizing specific applications to send messages
• Limiting access to an application to specific IPs

Middleware adds to or removes data by:

• Adding content such as client certificates to the header of requests
• Defining rules for which requests will be binned
• Limiting the number of simultaneous, in-flight requests
• Imposing rate limits to make sure services are treated fairly
• Protect systems from stacking requests to unhealthy services

Middleware aggregates data from different applications by:

• Defining reusable combinations of other pieces of middleware
• Combining multiple messages into one when the information is the same

Having this features list in mind, let’s walk through an example scenario to illustrate how middleware might affect data. Imagine you have an Application A that wants to converse with an Application B. Your middleware will collect the message, digest the content, and pass it along to Application B.

Along the way, it will affect the message in several ways. Say Application A uses the REST protocol, but Application B is an SQL database. The middleware will translate the message from HTTP into SQL to be understood by Application B. It will validate the security of Application A, authorizing it to communicate with Application B. It will ensure the message meets the requirements you’ve outlined, such as not exceeding a certain size. It will also add a timestamp to the message, as that is useful to the business.

The Nastel Platform supports all forms of middleware monitoring and management.