What is Microservice?

The microservice architecture is a variant of service-oriented architecture, in short, SOA structural style. It presents an application as a collection of many weakly associated services. In other words, in microservices architecture, a single application is composed of many independently deployable, fine-grained smaller services, and the protocols are lightweight.

Microservices architecture can be adopted for serverless computing, cloud-native applications, and applications using small container deployment.

Characteristics of Microservices

The characteristics services offered by the microservices architecture are:

• The services are processes that connect over a network to accomplish a target using protocols like HTTP.
• Services are prepared to meet business capabilities.
• Suitable programming languages, software environments, databases, and hardware are used while implementing the services.
• The services are lightweight, bounded by contexts, messaging option enabled, independently deployable, autonomously developed, and decentralized.
• Microservices are developed and released via automated processes.

Comparison with Monolithic Applications

A microservice isn’t a layer inside a monolithic application, such as the backend-for-frontend, or the web controller. Rather, it can be said that a microservice is a self-contained part of a business having clear interfaces. According to Martin Fowler, DevOps with dedicated service monitoring and decentralized continuous delivery are required to develop, maintain, and operate microservices because microservices are higher in number than monolithic application implementations.

A monolithic application providing support to three functions needs to be scaled fully even if only one of these functions had a resource. Whereas, an individual microservice is scaled individually. Only the microservice having supports for the function with resource constraints is required to be scaled out. Thus, microservices provide cost and resource optimization advantages. Martin Fowler describes this architecture to be a continuous delivery software development where a modification of a small portion requires rebuilding and redeploying a small number of services.

From a strategic point of view, the microservices architecture works following the Unix philosophy — “ Do one thing and do it well”.

Advantages of Microservices for the Organization

There are a number of advantages of decomposing an application into several fine-grained services.

Modularity

The application becomes easier to understand, develop, maintain, and capable to withstand architecture erosion.

Easily Scalable

Microservices are implemented and deployed independently. Hence they run within different independent processes. Also, they are monitored and scaled independently.

Integration of Heterogeneous Legacy Systems

Microservices are used to modernize already existing monolithic applications. This modernization is done via an incremental approach.

Distributed Development

Microservices development work is divided into small autonomous teams, thus parallelizing development. They develop, deploy, and scale their respective service. These architectures are based upon continuous delivery and deployment.

Tools and Technologies Used in Microservices

Any modern tool or programming language can be used in the microservices architecture. However, there are certain core tools that are essential in developing microservices.

Containers

Docker is most closely associated with the microservices architecture building. Individual containers don’t have a load of their own OS. That’s why they are lighter than traditional VMs. Also, containers can spin up and down faster. This makes them a perfect option to match smaller services found with microservices. With the growth of services, managing a large number of containers became necessary. Kubernetes, which is an open-source container orchestration platform, soon became the most popular orchestration solution.

API Gateways

Microservices often communicate through API. It acts as an intermediary layer between the clients and services. An API gateway becomes a reverse proxy for clients. It routes requests, fans out requests through multiple services, and offers an added security. Multiple technologies can be used for the purpose of API gateways implementation. But, in the case of containers and Kubernetes, the API gateway is implemented using Istio or Ingress.

Serverless

In the case of serverless architecture, the unit of execution isn’t a small service, but a function. Functions are smaller than microservices. A few lines of code often make a function. The common ground between the Functions-as-a-Service (FaaS) and serverless architectures is they both create smaller deployment units and scale as per the demand.

Concerns about Microservices

Some concerns regarding the microservices are:

• Testing and deployment require more work.
• Moving from monolithic applications to microservices increases management complexity
• Inter-service call costs are high.
• There isn’t any particular time to begin and end a microservice.
• It’s often challenging to develop and give support to a number of services.
• Logging data can be inconsistent across services.
• New versions can be the cause of backward compatibility issues.
• Applications require more network connections. This can higher connectivity issues.

A DevOps approach can solve many of these issues. However, the challenges can’t stop non-users from going with microservices, or users from committing more into microservices. An IBM survey reveals 56% of non-users are very likely to adopt microservices within the coming two years, and 78% of current users will likely increase their effort, money, and time invested in microservices.

Conclusion: Microservice is the Right Tool for Your Job

In n-tier architecture patterns, a software application shares a common stack having a large relational database. This database supports the whole application. This has several drawbacks. Every component of the application needs to share a common stack, database, and data model. It makes the architecture clumsy. Also, it becomes the source for the developers who are aware of a better way to build these components.

On the flip side, components in a microservice architecture are deployed independently. They connect over some combination of REST, event streaming, and message brokers. So, the stack of each individual service can be optimized for that particular service.

Microservice is the right tool for your business because an application made up of multiple smaller services is easier to manage and less expensive to evolve using the latest technologies.