What is a Distributed Application? Definition and Examples

A distributed application is a program that runs on one or more computers simultaneously and communicates through a network. In this blog post, we’ll dive into how distributed applications work, how they differ from standalone or traditional applications, how you can use them, their advantages and disadvantages, and some of the tools and technologies you can use to build them.

How Do Distributed Applications Work?

Applications of distributed computing interact to achieve a specific goal or task. You can store them on either servers or cloud infrastructure platforms. Distributed applications can be relatively simple, involving a single client computer and server, or more complex involving multiple client computers and servers—it primarily depends on how you plan to use them.

Distributed applications connected over a network

It’s also important to note that some distributed applications are two separate software programs consisting of front-end (client) and backend (server) applications. The front-end of the operation runs on the client computer and requires minimal processing power, while the backend requires a lot more processing power, a more dedicated system, and runs on a server computer.

In other distributed applications, the functionality separates into smaller, independent parts. These applications comprise individual microservices that handle different concerns within the broader application. In a cloud-native environment, the individual components typically run as containers on a cluster. We’ll go into more detail on how a distributed application is built later in this blog.

Standalone vs. Distributed Applications

Standalone applications rely on a single system to run. Because of this, all processing, data storage, and retrieval are from a single machine or server. If the application is a client-server model, the software will run on either the client or the server the client accessed. These applications are much simpler to maintain and develop and do not require infrastructure for communication and coordination between different systems. Since the applications do not rely on a network to communicate, they are not prone to communication failure due to network faults.

However, this also means these systems have limited capabilities and aren’t scalable. An application running on a single system is a single point of failure – if the system fails, the application is no longer available. They can also negatively impact developer velocity as they grow because more developers need to work on a shared codebase that doesn’t necessarily have well-defined boundaries.

On the other hand, distributed applications are interconnected machines capable of processing, data storage, and retrieval through multiple systems. They can run on both the server and the client simultaneously. The advantage of using distributed applications is that it provides reliability—if a system running an application goes down, another one can resume the task. The overall system can tolerate more application faults. They can also use horizontal scaling, which is impossible with standalone applications. However, these advantages come at the cost of increased complexity and operational overhead.

How Can I Use Distributed Applications?

Consider applications that run in hospitals, banks, or other service-oriented organizations. Because the same software runs on multiple computers, it allows people to work on the same record from the same or different locations editing different aspects of the record such as logging data, updating addresses, and retrieving transaction information. 

Common use cases for distributed applications include:

• • Web browsers (Tor)
  • E-commerce websites (Amazon, eBay)
  • Blockchain applications (Bitcoin, Ethereum)
  • Cloud computing platforms (AWS, Microsoft Azure)
  • Distributed databases (Couchbase, Apache Cassandra)
  • Peer-to-peer file-sharing networks (BitTorrent)

Any application that stores data from one location and retrieves it from another can be considered a distributed application. To understand what architecture is appropriate for a particular use case, we should look into the different types of distributed applications a developer can create.

Distributed Application Examples

Distributed applications leverage the principle of distributed systems. The most commonly used application architectures can be broadly organized into the following categories based on their underlying network architectures:

Client-server architecture: This is the most basic distributed system in which the server and client communicate. Communications include message passing, data collection, and calculations.

• • • Three-tier architecture: This is a client-server architecture organized into three tiers: the presentation, application, and data layers. It uses separate layers for each function of the program. The presentation layer displays the user-facing interface, the application layer is responsible for accessing and processing data from the database, and the data layer is where all the data and information are hosted and stored.
    • N-tier architecture: This differs from the three-tier architecture because each function runs on a separate machine or cluster.

Peer-to-peer architecture: In this system, each computer acts as a node for communication. Working as a node for communication means that each computer is a server and a client. It doesn’t have a centralized server like the previous architecture. Each system manages itself in a peer-to-peer network, making it easier to set up and handle.

Microservices architecture: This architecture structures an application as a collection of small, loosely coupled, and independently deployable services. An application can be decomposed into highly cohesive services, each representing a specific business capability or functionality.

Service-oriented architecture: In this approach, applications are built as a collection of services that communicate with each other through standardized protocols, promoting loose coupling and reusability of services.

Advantages of Distributed Applications

The advantages of using distributed applications are:

• • They have the capability of scaling horizontally. They take advantage of the scaling features of distributed systems and can expand themselves by adding new servers and systems that increase the capacity and operations of a network. Horizontal scaling allows them to easily implement applications on new systems without affecting the original network.
  • They’re tolerant of failures or software faults, making them very resilient. Because the applications run on multiple systems, it allows them to work independently. A failure of an application or a breakdown of a machine doesn’t impact the other applications in the network.
  • Due to the distributed nature of the application, the response time is much faster, giving it the advantage of low latency. 
  • Autonomy is another advantage of distributed applications. As the system shares data, each user or site retains control over locally stored data and resources. It also reduces the risk of a system-wide failure or data manipulation.
  • Distributed applications can also be cost-effective in the long run, as multiple computers work together by sharing resources over a network.

Disadvantages of Distributed Applications

The disadvantages of distributed applications are:

• • A distributed application introduces increased design complexity. There is a lot of operational overhead in maintaining, implementing, and troubleshooting issues. 
  • Using numerous servers, systems, and databases increases the risk of security breaches, data issues, and information leakage. However, you can counter this by taking security measures and running protection programs on systems and servers at all locations.
  • Since distributed applications connect over a single network, any issues or faults can lead to a communication breakdown among the applications.

Tools and Technologies for Building Distributed Applications

Building distributed applications requires a fair amount of skill and understanding of distributed system architectures, frameworks, middleware architecture, and databases. The tools you choose depend on the application’s requirements, programming languages, and desired functionality and characteristics. Most people turn to tools like Docker and Kubernetes for deploying and managing distributed applications. They provide containerization approaches and orchestration capabilities for scaling, load balancing, and managing distributed deployments. Cloud platforms like AWS and Microsoft Azure also have IaaS and SaaS capabilities, making it possible to use them for building scalable distributed applications,

Conclusion

In this blog, we covered the basics of distributed applications, how they differ from traditional standalone applications, how and where to use them, and the advantages and disadvantages of implementing such applications. If you’re interested in creating your own distributed applications check out the following resources:

• • Creating Distributed Applications in Java
  • Writing your First Distributed Python Application with Ray

If you would like to know more about how distributed databases work or how Couchbase enables high-performance applications with distributed caching, give the following resources a read:

• • Distributed Databases: An Overview
  • High-Performance Applications With Distributed Caching