A monolithic application can be defined in a variety of ways, such as a legacy program or an organically evolved codebase. It can also be defined as a lack of domain clarity and module boundaries in an application. Further, A monolithic application, is one that expanded over time, became unmanageable and incredibly difficult to understand, and had little cohesion and high coupling. A microservice architecture, on the other hand, paves the way for businesses to enable the rapid, frequent, and dependable delivery of a wide range of applications wherein the Software is composed of small independent services that communicate over well defined API's
As a result of benefits provided by Microservices based Architecture, various enterprises throughout the world are devoting resources to transition their monolithic apps to microservices.
However, transforming monolithic apps into microservices is a difficult undertaking. This is because a microservice design encourages the development of an application comprised of numerous independent services that encapsulate business functions.
Once converted to microservices, each service provides an API application that is discoverable and self-service. Given that converting a monolithic application to a microservice is a difficult task, let's look at some of the disadvantages of monolithic applications for businesses.
What is monolithic and microservices based architecture?
Monolithic apps are intended to manage a variety of connected tasks. They are usually complex applications with multiple tightly coupled functionality.
Consider the case of a monolithic ecommerce SaaS application. A web server, a load balancer, a catalogue service that serves up product images, an ordering system, a payment function, and a shipping component are all possible components.
Monolithic tools, as you may expect, contain massive code bases due to their enormous breadth. Making a minor modification to a single function may necessitate compiling and testing the entire platform, which contradicts the agile approach that today's engineers want.
In contrast to the monolithic approach, a microservices architecture involves smaller applications deployed independently as loosely coupled services, tied together through application integration. With microservice applications, the business logic may encompass multiple platforms, including software as a service, on-premises databases, and in-house-developed applications that meet needs that no SaaS application handles.
From a software engineering perspective, microservices can be simpler to develop. They’re smaller in scope and therefore smaller in size, which makes it easier for developers to improve them through continuous integration and continuous delivery (CI/CD). They can be written in any programming language. And they can communicate with other microservices through APIs.
An application programming interface (API) is a set of programming calls that expose the functionality of an application to developers. APIs make it simpler to develop integrated applications by offering an easy way to pass credentials and data between applications.
Monolithic v Microservices
Which architecture is better? The answer depends individually on each organizations requirements. Businesses should consider the following criteria:
Ease of implementation – You may imagine that because the software comes from a single vendor, monolithic systems would be easier to implement. This isn't always the case. Due to the complexity of monolithic systems, they may be as difficult to implement as several independent platforms. One advantage they may have is that monolithic systems are a one-stop shop for support — but only if the vendor has a strong reputation for support.
Lock-in of vendors — Monolithic systems typically seek to handle a wide range of related functions. A monolithic web hosting platform, for example, may comprise firewalls, load balancing, and a content distribution network in addition to a web server that processes HTTP requests on the server side.
Data control and ownership – Monolithic systems make it difficult for corporations to combine data from their systems. Typically, you can only use your data within the monolith. A monolithic analytics system that contains data integration, ETL data pipelines, a data warehouse, and analytics software, for example, may not include tools that allow businesses to access their own data in order to connect it with other systems or conduct analytics using different software.
Drawbacks of Monolithic Applications
Size and Complexities Limitation Monolithic applications are highly constrained by Size and complexities. To make an application bigger, the organization has to incorporate more services into it, making it slower to deploy and execute.
Difficult to Update Updating a monolithic application is one of the most daunting tasks for any business. The reason being, to update a monolithic application, organizations have to redeploy the entire application costing them time and money. Moreover, if an organization manages to update a monolithic application, the changes are not very well understood by the stakeholders; hence rigorous manual testing is required.
Poor Scalability Monolithic applications can be challenging to scale when different modules have conflicting resource requirements. This because several services call for resources that are interconnected with other services of the application. Therefore, when called, the engagement of resources avoids avoid hampering the scalability of the application.
Meager Reliability Reliability is one of the most impacting factors propelling the stakeholders to migrate monolithic applications to microservices. For instance, in the case of a bug, the entire process of the monolithic application is hampered. Moreover, the application might have the same service for multiple instances. In that case, the bug will reflect an entire application.
Looking at drawbacks, you might want to know the benefits of microservice architecture over monolithic applications. Let’s have a look:
Benefits of Microservices
Smoothen the Complexities The microservice architecture tackles over complexities of a monolithic application by decomposing the application into a set of manageable services. These services are faster to develop and easier to understand, making them swift to use and maintain.
No Barriers for New technologies Adoption Microservice architecture reduces the barrier of adopting new technologies. The architecture provides this flexibility as developers are free to choose whatever technologies make sense for their service and not bounded to the choices made at the start of the project.
Independent Deployment The architecture allows businesses to deploy microservices independently. This makes continuous deployment possible for organizations.
Better Agility Any fault in a microservices application affects only a particular service and not the whole solution. So all the changes and experiments are implemented with lower risks and fewer errors.
Since now know the drawbacks of monolithic applications and benefits of microservice architecture for the same applications. Now let’s look at how you can modernize your monolithic application by migrating to microservice:
Step 1: Identify the Logical Component
There are three major components with the data used in the system:
Data objects
Data actions
Job to perform
The logical construct of the data that is being used in the system is data objects. The data actions are the commands used on one or more data objects, possibly on different types of data, to perform a task. Whereas the job to perform is the function called to perform a task on the available data.
While combining the multiple systems into a unified approach, all the three components data objects, data actions, and jobs to perform for each system must be identified. These components are implemented as modules in the codebase. Identifying these components will allow the system architects to determine the actions to be performed on the data sets that shall come in handy in the later phases of the application.
Step 2: Flatten or Refractor Components
Once all the modules and components are uniquely identified and categorized, the businesses must organize these groups internally. The components that have similar functionalities must be addressed before the implementation of microservice architecture. In the end, there must be one microservice to perform a particular task.
Step 3: Identify the Dependencies of the Components
Upon identifying and reorganizing the components for migrating from a monolithic application to microservices, the system architects must identify the dependencies between the components. Architects can perform this task using static analysis of the source code to search for calls between different libraries and datatypes.
Step 4: Components Group Identification
After the components and dependencies are identified, the architects must focus on grouping the components into cohesive groups that can transform into microservices or at least macroservices. However, the distinction between micro and macro services is not essential in this step. This step aims to identify a small set of objects and their constituent actions that should be logically separated in the final system.
Step 5: APIs for Remote User Interface
The remote user interface is the only mode of communication among the system, its components, and the system’s users. The remote user interface must be scalable to adopt new features and technologies as the system evolves over the period.
The interface must be usable during migration and also once the microservice is deployed. Since the components are likely to change as they are worked upon, the remote user interface must manipulate the data when migrated from monolithic to microservices
This step aims to develop a unified API through which the user interfaces with the system and manipulates the data. The remote user interface is just a communication platform for the user, machines, and data. Everything else depends on this API.
Hence, it should be designed and developed to ensure the existing data interactions are not altered significantly. Instead, it should be scalable enough to encapsulate new data sets, functionalities, objects, attributes, and actions as they are identified and made available.
Once the API layer is in place, all new functionality should be added through the API, not through the legacy applications.
Step 6: Migrate the Components to Macroservice
Macroservices tends to be more receptive towards sharing data repositories and allow more complex data object interactions. Therefore it is advisable to this step as an interim process while migrating your monolithic application to microservices.
Not moving to microservice is because of the complexity of monolithic applications since they might be built using intertwined logics that may cause issues while converting to microservices.
The goal of this step is to move the components to separate projects and create separate deployments. At a minimum, each microservice should be independently deployable from within the system’s continuous integration (CI) and continuous deployment (CD) pipeline.
Step 7: Migrate Macroservice to Microservice
Once the components are migrated to macroservice, grouped and organized, the system architects must migrate these components of a monolithic application to microservice from macroservice. Using macroservice as an interim process makes the migration easy and quick as it provides further knowledge into ways to further separate these components into microservices.
Step 8: Deployment and Testing
Once a microservice or microservice is deployment ready, the next step is integration testing and deployment. The monolithic system must be configured to use the new service for its data needs instead of its legacy data store.
Finding all calls to the datastore from within the monolithic legacy system can be challenging. In a testing environment, it might be possible to remove the legacy data related to the migrated datasets for which the new microservice is now responsible.
Today businesses are in a constant race to update their infrastructure and outdated systems to avoid the challenges of legacy IT systems. These systems are the core of the growth of an organization therefore keeping them up-to-date is highly important.
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