Microservices is a new age architectural trend in software development used to create and deploy large, complex applications. Today's top tech players like Amazon, Uber, Netflix, Spotify, and more have also made the transition. It’s always essential for tech professionals to stay ahead of the market by mastering in-demand technologies and Microservices is the one you need to master. This Microservices tutorial will help you get acquainted with everything you need to know to get started with Microservices.

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Microservices Tutorial for Beginners

Before getting started with Microservices, we all know about an architectural pattern called monolithic architecture, which prevailed initially in the market. There are certain disadvantages of using this architectural pattern, but first, let's understand precisely what Monolithic Architecture means.

Monolithic Architecture

Monolithic is something composed of a single piece. According to layman terms, Monolithic architecture is similar to a big container that clubs all application components together into a single package.

Let's see an example of this Monolithic Architecture to understand how the applications built on this framework, how they perform, and how they communicate.

Refer to the client-server model shown below

Client Server Model

When a user opens a web User Interface, just views a website. But, behind the scenes, the server-side application has different features which handle it all together.

Features like handling HTTP requests, executing domain-specific logic, and retrieving data from the database are built on a single framework. So if any of the components won't work, the entire system goes down. Also, if any of the features get updated, the whole system needs to rebuild. These were the significant challenges for developers working on monolithic architecture.

Also, there are several other challenges with Monolithic Architecture. Let's look at them one by one now:

Monolithic Architecture Challenges (Drawbacks)

  • Agility - Monolithic architecture can accommodate the new changes to the application but with less agility. Developers have to build everything for every minor change. 
  • Unscalable - Scalability is nothing but the capability of a system/program to better handle work growth. Let's assume an eCommerce application is gaining a lot of customer attraction and wants to scale the application to gain more new customers.
  • Developers cannot scale the application simultaneously; whenever a new feature should be added/updated, they have to create new instances of the application. Also, different modules have conflicting resource requirements.
  • Fault Tolerance - A bug in any module can potentially bring down the entire process. It impacts the availability of applications.
  • Hybrid Technologies - Monolithic applications have a barrier to adopt new technologies. Since changes in frameworks or programming will affect an entire application, it is expensive.
  • Blocks Continuous Development - All features of the application cannot be built and deployed simultaneously.
  • Slow development - Development in monolithic apps is slow since each feature needs to build one after the other.

All these challenges were the main reasons that led to the evolution of Microservices. So now let's understand What is Microservices in simple words?

What are Microservices?

Microservices architecture or simply Microservices - is an architectural style that structures a single application into a collection of services that are independently deployable, loosely coupled, organized around business capabilities, and are easily maintainable and testable. Each service runs its own process and often communicates with each other over messaging or HTTP using lightweight protocols.

The trend for microservices is increasing in recent years as it enables rapid and reliable delivery of large, complex applications (one of the most critical skills for Java developers). Microservices can be thought of as the next form of Service Oriented Architecture (SOA).

-------         Related Article: Microservices vs SOA         -------

Refer to the below diagram to understand how the Microservices architecture provides better scalability, how different components can be worked together, and how each component can be handled individually without impacting the entire application.

Microservices Architecture

A microservices architecture consists of small, autonomous services, and each one is self-contained and implements a single business capability. All these services have their execution environments and load balancers to perform different functionalities and capture their data. They communicate with each other through HTTP REST/Message bus for performing automation and monitoring capabilities. API gateway acts as a communicator to pass the request of the client to the internal architecture.

Let's understand the functionalities of these components one by one:

  • Clients - Different users send requests from various devices. 
  • Identity Providers - The client requests are authenticated by Identity providers and then communicated to API Gateway.
  • API Gateway - Handles client requests.
  • Message Formats - They communicate through two message types such as Synchronous and Asynchronous.
  • Data Handling - Each Microservice owns a private database to capture their data and execute the respective business functionality. Also, Microservices databases are updated through their API service only.
  • Static Content - Houses all the content of the system.
  • Management - This component is responsible for balancing the services on nodes and identifying failures.
  • Service Discovery - This component acts as a guide to find the route of communication between microservices.
  • Content Delivery Networks - Delivers content to the distributed end-users.
  • Remote Service - Provides a dynamic, transport-independent, modular way to expose microservices.

------        Related Page: Security in Microservices         ------

Microservices Architecture Example

Let's look at an example of an eCommerce application built with Microservices Architecture.

eCommerce application with Microservices Architecture

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In the Monolithic Architecture, all the components merge into a single module. But, in Microservices Architecture, they spread out into individual modules(microservice).  

Here, each feature (Offer, New, Cart, Customer services, and so on) allotted with a different microservice, managing their data, and performing other functionalities. Every microservice focuses on a single business capability. Through that, we can deploy individual features whenever required again and again without affecting the performance of the entire application.

These individual deployable units communicate with each other through a well-defined interface called REST or message bus.

By now, you might have understood what the functionalities of microservices were and how they communicate. Let’s discuss the solid principles of Microservices.

Microservices Principles

The key principles of Microservices are:

  • Single Responsibility principle - It states that any class or module in microservices should have a single responsibility. Having multiple responsibilities lead to tight coupling and result in fragile designs that are hard to evolve and can break into unexpected ways upon changing.
  • Loose Coupling - Dependencies between services are minimized through the loose coupling.
  • Fault Tolerance - Microservices will be necessarily built fault-tolerant so that failures on the side of its collaborating services will have less impact on its own SLA. 
  • Infrastructure automation - In the microservice approach, each service is built by embedding all dependencies and running as standalone.
  • Deployment - Microservices are platform agnostic. It implies the services designed and deployed independently without affecting others.

Now, you know the principles under which microservices are designed. Let’s see the major differences between both Microservices and Monolithic architectures. 

Microservices Architecture vs Monolithic Architecture

The below diagram illustrates both Microservices and Monolithic architecture patterns.

Architecture Patterns

Following table details the differences between both architectures:

Microservices Architecture Monolithic Architecture
Microservices architecture contains various microservices for each feature handling their database. Monolithic Architecture contains a single framework for all the features on a single database.
It improved fault isolation. If any service goes down, another will continue the service. Fault isolation is problematic. If one service fails, the entire system goes down.
Microservices architecture remains decoupled so that one service function doesn't affect the other. Monolithic architecture tends to get tightly coupled and becomes complicated as the application evolves, making it challenging to separate services for coding, scalability, etc.
Enables each service to be scaled independently. Application scaling is challenging.
No cross-dependencies between codebases. One function depends on other services.
Quickly adopts emerging technology stack. Cannot adopt new technologies.
Microservices supports continuous delivery and deployment. Continuous deployment is complex
Easy to maintain since each service is relatively small and changes done quickly. Hard to maintain
Better deployability (enables each microservice to be deployed independently) Should redeploy the entire application on each update

Frequently asked Microservices Interview Questions

Types of Microservices

Microservices are of two types:

1. Stateless microservices

Stateless microservices are the building blocks of a distributed system. They don’t maintain a session state between requests. If any service is removed, it won't affect the overall performance logic for the service.

2. Stateful Microservices

Compared to stateless microservices, stateful microservices are less preferred in real-life. They maintain session information in the code. And when more than two services interact with each other, they keep a service request state.

This is about the types of microservices. Since every architectural pattern has its pros and cons, now it's essential to know the Microservices advantages and disadvantages before adopting it. 

Microservices Advantages and Disadvantages

Microservices Advantages

The advantages of Microservices are strong enough to have convinced some big players like Netflix, eBay, etc., to adopt the methodology. Let’s discuss them one by one:

1. Microservices are easily scalable.

Since the services are separate, you can easily scale the needed ones at the required times instead of the complete application.

2. Microservices reduces downtime through fault isolation.

Large apps can remain unaffected for single module failure.

3. Smaller and faster deployments

Microservices can be deployed independently, enabling continuous improvements and faster app updates.

4. Ease of understanding

With added simplicity, developers can easily understand the functionality of a service.

Microservices Disadvantages

There are a few disadvantages to Microservices. Some of them are listed below:

  • High Operational Overhead - Microservices are frequently deployed on their containers or virtual machines, causing an increase in VM wrangling work.
  • Perceptibility - As we know, microservices contain minimal services to deploy and maintain. It becomes tough to monitor the problems within it.
  • Configuration Management - This one is another major challenge of microservices. As it contains several small services, there is a great need to manage all services configurations across various environments. 
  • Debugging - It becomes difficult for a developer to check every service of architecture for an error. And debugging an error in each of those services is very complicated.
  • Automating the Components - Automate the entire cycle from the build, deployment to monitoring becomes more complicated.
  • Consistency - Maintaining data consistency between services is a challenging task.
  • Testing - Testing the interactions between services becomes more complicated.
  • Communication between services is complex - Inter-service communication and dealing with partial failure implementation is challenging.

Now in this Microservices Tutorial, let us discuss a few Java microservices frameworks.

Java Microservices Frameworks

There are several microservices frameworks that you can use for developing Java. Some of the most popular are listed below:

1. Spring Boot

Spring Boot is the leading framework to build microservices applications in Java. It works on top of languages for Inversion of Control, Aspect-Oriented Programming, and others. Spring Boot is a mature, open-source, feature-rich framework with excellent documentation and a vast community. Spring boot projects include IO platform, Cloud, Framework, Security, Batch, Data, REST Docs, and so on. 

-------        Also Read: Microservices With Spring Boot         -------

2. Dropwizard

Dropwizard is a Popular open-source framework used for the rapid development of RESTful web services. This framework integrates the mature and stable Java libraries into a fully functional platform: Jersey for REST, Jetty for HTTP, and Jackson for JSON, FreeMarker, Mustache, and more.

We can setup Dropwizard using Maven by adding the latest version to the POM. 

In addition, it boasts high performance and operations friendliness for microservices application development. Similar to Spring Boot, Dropwizard apps are packed into JAR files with the Jetty application server embedded. 

3. Jersey

Jersey is an open-source framework used to develop RESTful web services in Java that support JAX-RS APIs implementations. The best thing about Jersey is it has exceptional documentation with examples.

4. Micronaut

It's a modern, JVM-based microservice framework used to build modular easily testable microservice apps. It provides all the tools needed to build full-featured microservice apps. It has out-of-box support for Kubernetes, service discovery, distributed tracing and serverless functions.

5. AxonIQ

It's a Java Microservices framework used for building microservices architecture in-line with Domain-Driven Design (DDD) principles. It also allows you to implement microservices patterns such as Event-Driven Architecture and Command-Query-Responsibility-Segregation (CQRS).

By now, you became familiar with frequently used Java microservices frameworks. Next, let us move forward and learn about the various tools utilized while developing applications on Microservices architecture.

Microservices Tools

Following are the popular microservices tools used for various functionalities:

1. Docker 

An open-source tool that allows building and deploying apps using containers. Developers can run an application as a single package using these containers.

2. Hystrix

Hystrix is a fault tolerance library developed to isolate access points to remote systems, services and 3rd party libraries.

3. AWS Lambda

This tool supports infrastructure-less servers for microservices builds and users charged on the pay-per-use rate. Mostly, we use this tool for hosting REST or API service in combination with the AWS API gateway.

-------         Also Read: AWS Lambda Tutorial         ------

4. Prometheus

Prometheus is a monitoring tool used to detect the strange patterns of Microservices.

5. Logstash

Logstash is an open-source tool used for checking the logs. It allows you to stash, centralize, and transform data of microservices.

6. RabbitMQ

This tool employs patterns to interact between microservices and also scales the application simultaneously. With this tool's help, you can connect microservices to solve problems of distributed systems.

7. Apache Kafka

Apache Kafka is a distributed stream processing platform used for data processing or API calls.

-------          Related Article: Kafka vs RabbitMQ         --------

Lastly, in this Microservices Tutorial article, we'll discuss the best practices to design microservices.

Microservices Best Practices

By now, you should have understood how shifting to microservices benefits development, operations, and deployment.

Here are the best practices for designing microservices architecture:

  • Initially, separate the data store for each Microservice.
  • Then keep the code at a similar level of maturity.
  • After that, separately build each Microservice respective to its feature and then deploy it into containers.
  • Finally, treat the servers stateless for communication.

Conclusion

This brings us to the end of this article, where we have learned what microservices are and how they benefit your enterprise architecture, best practices, etc. We hope you are clear with all that has been shared with you in this Microservices tutorial to get started.

We hope you found the article informative and useful. In case you have any doubt, please drop the query in the comment box.