Topic: Monolith Transformation

For those working within software architecture, the term “monolithic application” or “monolith” carries significant weight. This traditional application design approach has been a staple for software development for decades. Yet, as technology has evolved, the question arises: Do monolithic applications still hold their place in the modern development landscape? It’s a heated debate that has been a talking point for many organizations and architects looking at modernizing their software offerings.

This blog will explore the intricacies of monolithic applications and provide crucial insights for software architects and engineering teams. We’ll begin by understanding the fundamentals of monolithic architectures and how they function. Following this, we’ll explore microservice architectures, contrasting them with the monolithic paradigm.

What is a monolithic application?

In software engineering, a monolithic application embodies a unified design approach where an application’s functionality operates as a single, indivisible unit. This includes the user interface (UI), the business logic driving the application’s core operations, and the data access layer responsible for communicating with the database. Monolithic architecture often contrasts with microservices, particularly when discussing scalability and development speed.

Let’s highlight the key characteristics of monolithic apps:

• Self-contained: Monolithic applications are designed to function independently, often minimizing the need for extensive reliance on external systems.
• Tightly Coupled: A monolith’s internal components are intricately interconnected. Modifications in one area can potentially have cascading effects across the entire application.
• Single Codebase: The application’s entire codebase is centralized, allowing for collaborative development within a single, shared environment —  a key trait in monolithic software architecture.

A traditional e-commerce platform is an example of a monolithic application. The product catalog, shopping cart, payment processing, and order management features would all be inseparable components of the system. A single monolithic codebase was the norm in systems built before the push towards microservice architecture.

The monolithic technology approach offers particular advantages in its simplicity and potential for streamlined development. However, its tightly integrated nature can pose challenges as applications become complex. We’ll delve into the advantages and disadvantages in more detail later in the blog. Next, let’s shift our focus and understand how a monolithic application functions in practice.

How does a monolithic application work?

When understanding the inner workings of a monolithic application, it’s best to picture it as a multi-layered structure. However, depending on how the app is architected, the separation between layers might not be as cleanly separated in the code as we logically divide it conceptually. Within the monolith, each layer plays a vital role in processing user requests and delivering the desired functionality. Let’s take a look at the three distinct layers in more detail.

1. User interface (UI)

The user interface is the face of the application, the visual components with which the user interacts directly. This encompasses web pages, app screens, buttons, forms, and any element that enables the user to input information or navigate the application.

When users interact with an element on the UI, such as clicking a “Submit” button or filling out a form, their request is packaged, sent, and processed by the next layer – the application’s business logic.

2. Business logic

Think of the business logic layer as the brain of the monolithic application. It contains a complex set of rules, computations, and decision-making processes that define the software’s core functionality. Within the business logic, a few critical operations occur:

• Validating User Input: Ensuring data entered by the user conforms to the application’s requirements.
• Executing Calculations: Performing required computations based on user requests or provided data.
• Implementing Branching Logic: Making decisions that alter the application’s behavior according to specific conditions or input data.
• Coordinating with the Data Layer: The business logic layer often needs to send and receive information from the data access layer to fulfill a user request.

The last functionality discussed above, coordinating with the Data Layer, is crucial for almost all monoliths. For data to be persisted, interaction with the application’s data access layer is critical.

3. Data access layer

The data access layer is the gatekeeper to the application’s persistent data. It encapsulates the logic for interacting with the database or other data storage mechanisms. Responsibilities include:

• Retrieving Data: Fetching relevant information from the database as instructed by the business logic layer.
• Storing Data: Saving new information or updates to existing records within the database layer.
• Modifying Data: Executing changes to stored information as required by the application’s processes.

Much of the interaction with the data layer will include CRUD operations. This stands for Create, Read, Update, and Delete, the core operations that applications and users require when utilizing a database. Of course, in some older applications, business logic may also reside within stored procedures executed in the database. However, this is a pattern that most modern applications have moved away from.

The significance of deployment

In a monolithic architecture, the tight coupling of these layers has profound implications for deployment. Even a minor update to a single component could require rebuilding and redeploying the entire application as a single unit. This characteristic can hinder agility and increase deployment complexity – a pivotal factor to consider when evaluating monolithic designs, especially in large-scale applications. This leads to much more involved testing, potentially regression testing an entire application for a small change and a more stressful experience for those maintaining the application.

What is a microservice architecture?

As applications have evolved and become more complex, the monolithic approach is only sometimes recognized as the optimal way to build and deploy applications. This is where the push for microservice architectures has swooped in to address the challenges of monolithic software. The microservices architecture presents a fundamentally different way to structure software applications. Instead of building an application as a single, monolithic block, the microservices approach advocates for breaking the application down into multiple components. This results in small, independent, and highly specialized services.

Here are a few hallmarks and highlights that define a microservice:

• Focused Functionality: Each microservice is responsible for a specific, well-defined business function (like order management or inventory tracking).
• Independent Deployment: Microservices can be deployed, updated, and scaled independently.
• Loose Coupling: Microservices interact with one another through lightweight protocols and APIs, minimizing dependencies.
• Decentralized Ownership: Different teams often own and manage individual microservices, promoting autonomy and specialized expertise.

Let’s return to the e-commerce example we covered in the first section. In a microservices architecture, you would have separate services for the product catalog, shopping cart, payment processing, order management, and more. These microservices can be built and deployed separately, fostering greater agility. When a service update is ready, the code can be built, tested, and deployed much more quickly than if it were contained in a monolith.

Monolithic application vs. microservices

Now that we understand monolithic and microservices architectures, let’s compare them side-by-side. Understanding their differences is key for architects making strategic decisions about application design, particularly when considering what is a monolith in software versus microservices architecture.

When to choose which

As with any architecture decision, specific applications lend themselves better to one approach over another. The optimal choice between monolithic and microservices depends heavily on several factors, these include:

• Application Size and Complexity: Monoliths can be a suitable starting point for smaller, less complex applications. For large, complex systems, microservices may offer better scalability and manageability.
• Development Team Structure: If your organization has smaller, specialized teams, microservices can align well with team responsibilities.
• Need for Rapid Innovation: Microservices enable faster release cycles and agile iteration, which are beneficial in rapidly evolving markets.

Advantages of a monolithic architecture

While microservices have become increasingly popular, it’s crucial to recognize that monolithic architectures still hold specific advantages that make them a valid choice in particular contexts. Let’s look at a few of the main benefits below.

Development simplicity

Building a monolithic application is often faster and more straightforward, especially for smaller projects with well-defined requirements. This streamlined approach can accelerate initial development time.

Straightforward deployment

Deploying a monolithic application typically involves packaging and deploying the entire application as a single unit, making application integration easier. This process can be less complex, especially in the initial stages of a project’s life cycle.

Easy debugging and testing

With code centralized in a single codebase, tracing issues and testing functionality can be a more straightforward process compared to distributed microservices architectures. With microservices, debugging and finding the root cause of problems can be significantly more difficult than debugging a monolithic application.

Performance (in some instances)

For applications where inter-component communication needs to be extremely fast, the tightly coupled nature of a monolith can sometimes lead to slightly better performance than a microservices architecture that relies on network communication between services.

When monoliths excel

Although microservice and monolithic architectures can technically be used interchangeably, there are some scenarios where monoliths fit the bill better. In other cases, choosing between these two architectural patterns is more based on preference versus a straightforward advantage. When it comes to monolithic architectures, they are often a good fit for these scenarios:

• Smaller Projects: For applications with limited scope and complexity, the overhead of a microservices architecture might be unnecessary.
• Proofs of Concept: A monolith can offer a faster path to a working product when rapidly developing a prototype or testing core functionality.
• Teams with Limited Microservices Experience: If your team lacks in-depth experience with distributed systems, a monolithic approach can provide a gentler learning curve.

Important considerations

It’s crucial to note that as a monolithic application grows in size and complexity, the potential limitations related to scalability, agility, and technology constraints become more pronounced. Careful evaluation of your application, team, budget, and infrastructure is critical to determine if the initial benefits of a monolithic approach outweigh the challenges that might arise down the line.

Let’s now shift our focus towards the potential downsides of monolithic architecture.

Disadvantages of a monolithic architecture

While monolithic programs offer advantages in certain situations, knowing the drawbacks of using such an approach is essential. With monoliths, many disadvantages don’t pop out initially but often materialize as the application grows in scope or complexity. Let’s explore some primary disadvantages teams will encounter when adopting a monolithic pattern.

Limited scalability

The entire application must be scaled together in a monolith, even if only a specific component faces increased demand. This can lead to inefficient resource usage and potential bottlenecks. In these cases, developers and architects are faced with either increasing resources and infrastructure budget or face performance issues in specific parts of the application.

Hindered agility

The tightly coupled components of a monolithic application make it challenging to introduce changes or implement new features. Modifications in one area can have unintended ripple effects, slowing down innovation. Suppose monoliths are built with agility in mind. In that case, this is less of a concern, but as complexity increases, the ability to quickly create new features or improve older ones without major refactoring and testing becomes less likely.

Technology lock-in

Monoliths often rely on a single technology stack. Adopting new languages or frameworks can require a significant rewrite of the entire application, limiting technology choices and flexibility.

Growing complexity and technical debt

As a monolithic application expands,  its software complexity increases, making the codebase more intricate and challenging to manage. This can lead to longer development cycles and a higher risk of bugs or regressions. In the worst cases, the application begins to accrue increasing amounts of technical debt. This makes the app extraordinarily brittle and full of non-optimal fixes and feature additions.

Testing challenges

Thoroughly testing an extensive monolithic application can be a time-consuming and complex task. Changes in one area can necessitate extensive regression testing to ensure the broader system remains stable. This leads to more testing effort and extends release timelines.

Stifled teamwork

The shared codebase model can create dependencies between teams, making it harder to work in parallel and potentially hindering productivity. In the rare case where a monolithic application is owned by multiple teams, careful planning must happen. When it comes time to merge features, there’s a lot of time and collaboration that must be available to ensure a successful outcome.

When monoliths become a burden

Although monoliths do make sense in quite a few scenarios, monolithic designs often run into challenges in these circumstances:

• Large-Scale Applications: As applications become increasingly complex, the lack of scalability and agility in a monolith can severely limit growth potential.
• Rapidly Changing Requirements: Markets that demand frequent updates and new features can expose the limitations of monolithic architectures in their ability to adapt quickly.
• Need for Technology Diversification: If different areas of your application would enormously benefit from various technologies, the constraints of a monolith can become a roadblock.

Transition point

It’s important to continually assess whether the initial advantages of a monolithic application still outweigh its disadvantages as a project evolves. There often comes a point where the complexity and evolving scalability requirements create a compelling case for the transition from monolith to microservices architecture. If a monolithic application would be better served with a microservices architecture, or vice versa, jumping to the most beneficial architecture early on is vital to success.

Now, let’s move on to real-world examples to give you some tangible ideas of monolithic applications.

Monolithic application examples

To understand how monolithic architectures are used, let’s examine a few application types where they are often found and the reasons behind their suitability.

Legacy applications

Many older, large-scale systems, especially those developed several decades ago, were architected as monoliths. Monolithic applications can still serve their purpose effectively in industries with long-established processes and a slower pace of technological change. These systems were frequently built primarily on stability and may have undergone less frequent updates than modern, web-based applications. The initial benefits of easier deployment and a centralized codebase likely outweighed the need for rapid scalability often demanded in today’s markets.

Content management systems (CMS)

Early versions of popular Content Management Systems (CMS) like WordPress and Drupal often embodied monolithic designs. While these platforms have evolved to offer greater modularity today, there are still instances where older implementations or smaller-scale CMS-based sites retain a monolithic structure. This might be due to more straightforward content management needs or less complex workflows, where the benefits of granular scalability and rapid feature rollout, typical of microservices, are less of a priority.

Simple e-commerce websites

Small online stores, particularly during their initial launch phase, might find a monolithic architecture sufficient. A single application can effectively manage limited product catalogs and less complicated payment processing requirements. For startups, the monolithic approach often provides a faster path to launching a functional e-commerce platform, prioritizing time-to-market over the long-term scalability needs that microservices address.

Internal business applications

Applications developed in-house for specific business functions (like project management, inventory tracking, or reporting) frequently embody monolithic designs. These tools typically serve a well-defined audience with a predictable set of features. In such cases, the overhead and complexity of a microservices architecture may need to be justified, making a monolith a practical solution focused on core functionality.

Desktop applications

Traditional desktop applications, especially legacy software suites like older versions of Microsoft Office, were commonly built with a monolithic architecture. All components, features, and functionalities were packaged into a single installation. This approach aligned with the distribution model of desktop software, where updates were often less frequent, and user environments were more predictable compared to modern web applications.

When looking at legacy and modern applications of the monolith pattern, it’s important to remember that technology is constantly evolving. Some applications that start as monoliths may have partially transitioned into hybrid architectures. In these cases, specific components are refactored as microservices to meet changing scalability or technology needs. Context is critical – a deep assessment of the application’s size, complexity, and constraints is essential when determining if there is an accurate alignment with monolithic principles.

How vFunction can help optimize your architecture

The choice between modernizing or optimizing legacy architectures, such as monolithic applications, presents a challenge for many organizations. As is often the case with moving monoliths into microservices, refactoring code, rethinking architecture, and migrating to new technologies can be complex and time-consuming. In other cases, keeping the existing monolithic architecture is beneficial, along with some optimizations and a more modular approach. Like many choices in software development, choosing a monolithic vs. microservice approach is not always “black and white”. This is where vFunction becomes a powerful tool to simplify and inform software developers and architects about their existing architecture and where possibilities exist to improve it.

Let’s break down how vFunction aids in this process:

1. Automated Analysis and Architectural Observability: vFunction begins by deeply analyzing the monolithic application’s codebase, including its structure, dependencies, and underlying business logic. This automated analysis provides essential insights and creates a comprehensive understanding of the application, which would otherwise require extensive manual effort to discover and document. Once the application’s baseline is established, vFunction kicks in with architectural observability, allowing architects to actively observe how the architecture is changing and drifting from the target state or baseline. With every new change in the code, such as the addition of a class or service, vFunction monitors and informs architects and allows them to observe the overall impacts of the changes.

2. Identifying Microservice Boundaries: One crucial step in the transition is determining how to break down the monolith into smaller, independent microservices. vFunction’s analysis aids in intelligently identifying domains, a.k.a. logical boundaries, based on functionality and dependencies within the monolith, suggesting optimal points of separation.

3. Extraction and Modularization: vFunction helps extract identified components within a monolith and package them into self-contained microservices. This process ensures that each microservice encapsulates its own data and business logic, allowing for an assisted move towards a modular architecture. Architects can use vFunction to modularize a domain and leverage the Code Copy to accelerate microservices creation by automating code extraction. The result is a more manageable application that is moving towards your target-state architecture.

Key advantages of using vFunction

• Engineering Velocity: vFunction dramatically speeds up the process of improving monolithic architectures and moving monoliths to microservices if that’s your desired goal. This increased engineering velocity translates into faster time-to-market and a modernized application.
• Increased Scalability: By helping architects view their existing architecture and observe it as the application grows, scalability becomes much easier to manage. By seeing the landscape of the application and helping to improve the modularity and efficiency of each component, scaling is more manageable.
• Improved Application Resiliency: vFunction’s comprehensive analysis and intelligent recommendations increase your application’s resiliency and architecture. By seeing how each component is built and interacts with each other, informed decisions can be made in favor of resilience and availability.

Conclusion

Throughout our journey into the realm of monolithic applications, we’ve come to understand their defining characteristics, historical context, and the scenarios where they remain a viable architectural choice. We’ve dissected their key advantages, such as simplified development and deployment in certain use cases, while also acknowledging their limitations in scalability, agility, and technology adaptability as applications grow in complexity.

Importantly, we’ve highlighted the contrasting microservices paradigm, showcasing the power of modularity and scalability it offers for complex modern applications. Understanding the interplay between monolithic and microservices architectures is crucial for software architects and engineering teams as they make strategic decisions regarding application design and modernization.

Interested in learning more? Request a demo today to see how vFunction architectural observability can quickly move your application to a cleaner, modular, streamlined architecture that supports your organization’s growth and goals.

Are you wondering about the differences between monolithic applications and microservices? It can be confusing, but as more companies move to a cloud-first architecture, it’s essential to understand these terms.

An enterprise application usually consists of three parts: a client-side application, a server-side application, and a database. Our focus is on the server-side application, which handles the business logic, interacts with various clients and potentially other external systems, and uses one or more databases to manage the data. This part is typically the most complex and requires most of the development and testing efforts. 

It may be built as one large “monolithic” block of code or as a collection of small, independent, and reusable pieces called microservices. Most legacy applications have been built as monoliths, and converting them to microservices has benefits and challenges.

What is a monolithic architecture?

A monolithic architecture is a traditional software design approach where all components of an application are tightly integrated into a single, unified codebase. Think of it as a large container housing the entire application’s functionality, including:

• User interface (UI): The frontend layer presents information to users.
• Business logic: The core application logic processes data and implements business rules.
• Data access layer: The component that interacts with databases or other data sources.

In this 3 tier architecture, the three tiers are not independent components and there are dependencies between classes across the layers which typically becomes very complex as the application evolves. This leads to a high risk of causing regressions when introducing changes to the code because it is hard to predict how a change in one class will impact others. The application is deployed as a single unit; for example, a Java WAR (Web Archive) is deployed into an application server or a native executable file.

While this approach offers simplicity in the early stages of development, it can lead to challenges as the application grows in size and complexity. The tight coupling of components can make it challenging to scale, update, or maintain individual parts without affecting the entire system. In contrast, microservices architecture, which we will cover later, addresses these issues by breaking down the application into smaller, independent services, making it easier to manage, scale, and maintain.

Advantages of a monolithic architecture

Understanding the benefits of monolithic and microservices architecture is critical to making an informed decision about the right approach for your project.

Simplified development and deployment

Monoliths excel in simplicity. A typical monolithic application, where all data objects and actions are handled by a single codebase and stored in a single database, makes development and deployment more straightforward, especially for smaller applications or projects with limited resources. There’s no need to manage complex inter-service communication or orchestrate multiple deployments.

End-to-end testing

End-to-end testing is typically easier to perform in a monolithic structure. Since all components reside within a single unit, testing the entire application flow is more streamlined, potentially reducing the complexity and time required.

Performance

In some cases, monolithic applications can outperform microservices regarding raw speed. This is because inter-service communication in microservices can introduce latency. With their unified codebase and shared memory, Monoliths can sometimes offer faster execution for certain operations.

Debugging

Monoliths often provide a more straightforward debugging experience. With all code residing in one place, tracing issues and identifying root causes can be more intuitive compared to navigating the distributed nature of microservices.

Reduced operational overhead

Initially, monolithic architectures may require less operational overhead. Managing a single application can be easier than managing a multitude of microservices, each with its own deployment and scaling requirements.

Cost-effectiveness

Monolithic architecture can be a more cost-effective option for smaller projects or those with limited budgets. However, the complexity of setting up and maintaining a microservices infrastructure can introduce additional expenses.

Remember, the ideal architectural choice depends on your project’s specific needs. While monoliths offer simplicity and ease of use, they may not be suitable for larger, complex applications where scalability, flexibility, and independent development are paramount.

Disadvantages of a monolithic architecture

While monolithic architecture offers simplicity and ease of use, it has drawbacks. These limitations become increasingly apparent as applications grow in size and complexity.

Scalability challenges

Monolithic systems can be challenging to scale. To cater to high workloads, you can either add more resources (CPU, memory) and/or replicate the entire monolith over multiple computational nodes with a load balancer, even if only specific components are experiencing high demand. This is inefficient resource utilization leading to increased costs.

Limited technology flexibility

Monolithic applications are built using a single technology stack. This can limit the ability to adopt new technologies or frameworks, as changes require rewriting a large part of the application.

Tight coupling and reduced agility

In a monolithic architecture, components are tightly coupled, making changes or updates to individual parts more challenging. This can slow development and deployment cycles, hindering agility and responsiveness to changing requirements. Also, testing the entire functional scope of a complex monolith is challenging, as is achieving sufficient coverage. 

Increased complexity over time

As monolithic applications grow, their data storage mechanisms typically rely on a single database, which can lead to an increasingly complex and difficult-to-manage codebase. This can result in longer development cycles, a higher risk of errors, and challenges in understanding the system’s overall behavior.

Single point of failure

Monolithic architectures represent a single point of failure. If a critical component fails, the entire application can go down, impacting availability and causing significant disruptions.

Deployment risks

Deploying updates to a monolithic application can be risky. Even minor changes require a full redeployment of the entire system, increasing the likelihood of introducing errors or unforeseen side effects.

Remember, the disadvantages of monolithic architecture become more pronounced as applications scale. For large, complex systems, the limitations of monoliths can significantly impact development, deployment, scalability, and overall agility.

What are microservices?

A microservice architecture consists of small, independent, and loosely coupled services. It offers significant benefits and challenges when migrating from a monolithic architecture to a microservices architecture. Microservices are small autonomous services organized around business or functional domains. A single small development team often owns each service.

Every service can be an independent application with its own programming language, development and deployment framework, and database. Each service can be modified independently and deployed by itself. A Gartner study shows that microservices can deliver better scalability and flexibility.

Advantages of microservices

There are many benefits to choosing a microservices architecture, including scalability, agility, velocity, upgradability, cost, and many others. The Boston Consulting Group has listed the following benefits.

Emphasis on capabilities and values

Well designed microservices correspond to functional domains, or business capabilities, and have well defined boundaries. Users of a microservice don’t need to know how it works, what programming language it uses, or its internal logic. All that they need to know is how to call an API (Application Programming Interface) method provided by the microservice (usually routed through an API gateway) and what data it returns. When designed well, microservices can be reused across applications and deliver business capabilities more flexibly.

Agility

A microservice is designed to be decoupled, so changes made to it will have little or no impact on the rest of the system. The developers don’t need to worry about complex integrations. This makes it easier to make and release changes. For the same reason, the testing effort can be focused, reducing testing time as well. This results in increased agility.

Upgradability

One of the biggest differentiators between monolithic applications and microservices is upgradability, which is critical in today’s fast-moving marketplace. You can deploy a microservice independently, making fixing bugs and releasing new features easier. 

You can also roll out a single service without redeploying the entire application. If you find issues during deployment, the erring service can be rolled back, which is easier than rolling back the full application. A good analogy is the watertight compartments of a ship—flooding is confined. 

Small teams

A well-designed microservice is small enough for a single team to develop, test, and release. The smaller code base makes it easier to understand, increasing team productivity. Microservices are not coupled by business logic or data stores, minimizing dependencies. All this leads to better team communication and reduced management costs.

Flexibility in the development environment

Microservices are self-contained. So, developers can use any programming language, framework, database, or other tools. They are free to upgrade to newer versions or migrate to using different languages or tools if they wish. No one else is impacted if the exposed APIs are not changed. 

Scalability

If a monolith uses up all available resources, it can be scaled by creating another instance. If a microservice uses up all resources, only that service will need more instances, while other services can remain as is. So scaling is easy and precise. The least possible number of resources is used, making it cheaper to scale.

Automation

When comparing monolithic applications to microservices, the benefit of automation can’t be stressed enough. Microservices architecture enables the automation of several otherwise tedious and manual core processes, such as integration, building, testing, and continuous deployment. This leads to increased productivity and employee satisfaction. 

Velocity

All the benefits listed above result in teams focusing on rapidly creating and delivering value, which increases velocity. Organizations can respond quickly to changing business and technology requirements.

How to convert monoliths to microservices

There are two ways of migrating monolithic apps to microservices: manually or through software automation.

A well-defined migration strategy is crucial for planning and executing the transition from monolithic applications to microservices. The migration process needs to consider several factors. The guidelines below have been recommended by Martin Fowler and are applicable whether you are trying to manually modernize your app or using automated tools.

Identify a simple, decoupled functionality

Start with functionality that is already somewhat decoupled from the monolith, does not require changes to client-facing applications, and does not use a data store. Convert this to a microservice. This helps the team upskill and set up the minimum DevOps architecture to build and deploy the microservice.

Cut the dependency on the monolith

The dependency of newly created microservices on the monolith should be reduced or eliminated. In fact, during the decomposition process, new dependencies are created from the monolith to the microservices. This is okay, as it does not impact the pace of writing new microservices. Identifying and removing dependencies is often the most challenging part of refactoring.

Identify and split “sticky” capabilities early 

The monolith may have “sticky” functionality that makes several monolith capabilities depend on it. This makes it difficult to remove more decoupled microservices from the monolith. To proceed, it may be necessary to refactor the relevant monolith code, which can also be very frustrating and time-consuming.

Decouple vertically

Most decoupling efforts start with separating the user-facing functionality to allow UI changes to be made independently. This approach results in the monolithic data store being a velocity limiting factor. Functionality should instead be decoupled in vertical “slices,” where each includes functionality encompassing the UI, business logic, and data store. Having a clear understanding of what business logic relies on what database tables can be the hardest thing to untangle.

Decouple the most used and most changed functionality

One goal of moving microservices to the cloud is to speed up changes to features existing in the monolith. The development team must identify the most frequently modified functionality to enable this. Moving this capability to microservices provides the quickest and most ROI. Prioritize the business domain with the highest business value to refactor first.

Go macro, then micro

The new “micro” services should not be too small initially because this creates a complex and hard-to-debug system. The preferred approach is to start with fewer services, each offering more functionality, then break them up later.

Migrate in evolutionary steps 

The migration process should be completed in small but atomic steps. An atomic step consists of creating a new service, routing users to the new service, and retiring the code in the monolith that has been providing this functionality so far. This ensures the team is closer to the desired architecture with every atomic step.

What are the challenges of migrating monoliths to microservices?

While the strategic benefits of microservices are clear, the technical hurdles involved in the migration process can be significant. Understanding these challenges is crucial for planning a successful transition.

Decomposition of the monolith

Breaking down a monolithic application into independent microservices is a complex task. Identifying service boundaries, managing dependencies, and refactoring code can be time-consuming and error-prone. Ensuring a smooth decomposition requires a deep understanding of the application’s domain and careful planning. Some teams try to use Domain Driven Design (DDD) techniques, such as event storming, to define the domains and their boundaries, but doing these whiteboard exercises may overlook critical details you can only discover by analyzing the actual implementation.

Data refactoring

Monolithic applications often rely on a single, centralized database. Migrating to microservices typically involves splitting this database into smaller, service-specific databases. This can involve complex data migration, ensuring data consistency across services, and managing distributed transactions. Pulling components and data objects out of the monolithic system often involves data replication, crucial for maintaining data integrity during the transition. Splitting the database requires a detailed understanding of how the various components are using the database tables and transactions.

Network latency and communication

Microservices communicate over a network, introducing latency that can impact performance. Designing efficient communication patterns, handling network failures, and managing potential bottlenecks are crucial for maintaining system responsiveness. Different approaches and protocols are used for microservices communications, such as using REST API, gRPC, or RabbitMQ. In some cases, microservices may exchange data over the data store instead of direct communications. Having a consistent approach for service-to-service communication is a key architectural decision.

Testing and monitoring

Testing and monitoring a distributed microservices architecture is more challenging than a monolithic one. Each service needs independent testing, and end-to-end testing becomes more complex due to the increased number of components and their interactions. Comprehensive monitoring and logging are essential to identify and address issues promptly.

Infrastructure and deployment

Microservices require a more sophisticated infrastructure and deployment pipeline. Each service needs independent deployment, scaling, and management, which can be a significant overhead compared to deploying a single monolith. Tools like containerization and orchestration platforms can help manage this complexity.

Technology diversity

Microservices allow for using different technologies for different services. While this offers flexibility, it also introduces challenges in managing multiple languages, frameworks, and libraries and ensuring their compatibility.

Using vFunction to expedite migrating from monoliths to microservices

vFunction architectural observability platform automates and simplifies the decomposition of monoliths into microservices. How does it do this?

The platform collects dynamic and static analysis data using two components: for dynamic analysis, an agent traces the running application, which samples the call stacks and detects the usage of resources such as accessing databases and I/O operation of files and network sockets. For static analysis, there is a component called “Viper”, which analyzes the application’s binary files to derive compile time dependencies and analyze the application configuration files (e.g.. Bean definitions). Both data sets are provided to an analysis engine running on the vFunction server, which uses machine learning algorithms, to identify the business domains in the legacy monolithic app.

The combination of dynamic and static data provides a complete view of the application. This enables architects to specify a new system architecture in which functionality is provided by a set of smaller applications corresponding to the various domains rather than a single monolith.

The platform includes custom analysis and visualization tools that observe the app running in real time and help architects see how it is behaving and what code paths are followed, including how various resources, such as database tables, files, and network sockets, are used from within these flows. The software uses this analysis to recommend how to refactor and restructure the application. These tools help maximize exclusivity (resources used only by one service), enabling horizontal scaling with no side effects. It handles code bases of millions of lines of code, speeding up the migration process by a factor of 15.

Many companies attempt the decomposition process using Java Profilers, Design and Analysis Tools, Java Application Performance Tools, and Java Application Tooling. However, these tools are not designed to aid modernization. They can’t help breaking down the monolith because they don’t understand the underlying interdependencies. So, the new architecture needs to be specified manually when using these tools.

Monolith to microservice examples

To illustrate how a monolith to microservices migration can be done, let’s look at a simple example of an e-commerce application called Order Management System (OMS) and how it could be refactored. The monolithic code of this application can be found here. As you can see in the readme file, it uses a classical 3-layer architecture:

The web layer contains a package for controller classes exposing all the functionality of the monolith along with data transfer object (DTO) classes.

The service layer contains three packages implementing all the business logic, including integration with external systems, and the persistence layer contains the entity and repository classes to manage all the data in a MySQL database.

Analyzing the actual flows and the application binaries, the application is re-architected as a system of services corresponding to business domains, as seen in the figure below. Every sphere represents a service, and every dashed line represents calls triggering the services. Every service is defined by a set of entry points, classes that implement it, and the resources it uses. The specifications of the services can be used as input for vFunction Code Copy to create an implementation baseline for the services out of the original monolithic code.

Watch this short video on architectural observability to see how vFunction transforms monoliths into microservices.

Conclusion

Companies want to move fast. The tools provided by vFunction enable the modernization of apps (i.e., conversion from monoliths to microservices) in days and weeks, not months or years.

vFunction’s architectural observability platform for software engineers and architects intelligently and automatically transforms complex monolithic Java or .NET applications into microservices. Designed to eliminate the time, risk, and cost constraints of manually modernizing business applications, vFunction delivers a scalable, repeatable model for cloud-native modernization. Leading companies use vFunction to accelerate the journey to cloud-native architecture. To see precisely how vFunction can speed up your application’s journey to a modern, high-performing, scalable, true cloud-native, request a demo.