Introduction to microservices. What are microservices and how do they work?

Although they may seem to be linked to Microsoft, microservices have much more in common with Netflix. Just a dozen, or so, years ago, they were thought to be just an experiment, now this software design architecture is becoming rapidly popular for building continuously deployed systems and adapted to the biggest, well-known platforms.

What’s more, in February 2020, the Cloud Microservices Market Research Report forecasted that the global microservice architecture market size will increase at a CAGR of 21.37% from 2019 to 2026 and reach $3.1 billion by 2026. No wonder, the approach that offers such application scalability, acceleration of development and flexibility, must have turned out to be a new trend conquering the IT world.

However, it’s a matter that still is vague or incomprehensible to many. To find out why microservices are gaining such popularity and recognition, delve into all of the details about them that we’ve listed below.

What are microservices?

Microservices, or microservice architecture, is a kind of the service-oriented architecture (SOA) structural style that organizes an application as a collection of individual services.

Such a construction implies some characteristics of services:

• independently deployable, autonomously developed and implemented using different technologies each, depending on what is the best solution;
• fine-grained and the protocols are lightweight;
• small in size, messaging-enabled, bounded by contexts, and decentralized;
• built and released with automated processes;
• organized around business capabilities;
• use technology-agnostic protocols such as HTTP.

The above features may sound a bit serious or complicated, so let’s clear any doubts by discussing how microservices work.

How do microservices work?

Microservices are most often compared to a monolithic architecture, a default approach to build an application. This traditional way assumes that the application is as a single and indivisible unit, has one large codebase, and no individual modules.

Microservices, in turn, are distinguished by their flexibility. Instead of a single, monolithic code, they propose building an application as a set of services. In this architecture, all functionality is broken down into independently deployable modules that communicate with each other using defined methods called API (Application Programming Interfaces). Each service has its scope and can be updated, deployed, and scaled apart from the others.

This approach gives many possibilities. The solution seems ideal for distributed teams thanks to the division of functionalities into completely independent blocks. As a result, large companies with distributed teams can work efficiently by assigning different microservices to different teams. But that’s not the only reason why many innovative tech companies are turning to microservices.

Why do we need microservices?

Microservices are more advantageous for complex and evolving applications. It’s an effective solution to handle a compound system with various functions and services. When it comes to innovation, developers can easily experiment without fear of causing problems elsewhere, as every component is independent and doesn’t cause the crash of the whole system.

Large-scale platforms with a big audience certainly need to minimize component size and memory consumption, so the use of microservices becomes essential for demanding operations.

Microservices can also help adapt faster to changing market conditions. Because microservices allow us to rapidly update and test applications, it’s possible to follow market trends and match products quicker.

Advantages of microservices

The service separation approach offers many opportunities and benefits:

• Scalability. Services can be scaled independently, e.g. those that require more resources, without the need to scale the entire application.
• Flexibility. As microservices are deployed apart from each other, it is easier to manage bug fixes and feature versions. The service can be updated without having to redeploy the entire application and roll back the update if something goes wrong.
• Small, dedicated teams. It enables the development of each of the services by one team, which therefore focuses only on the functionality of this service.
• Diversity of technologies. Each microservice can be made in a different technology, which allows for the selection of the most efficient solution for each part.
• Easy error fixing. If one microservice becomes unavailable, it does not disrupt the entire application, as long as all parent microservices can handle errors properly.

Disadvantages of microservices

Microservices also have their ugly side, which is also worth keeping in mind:

• Complexity. Although the individual services are simpler, the overall system is more complex.
• Data integrity. The individual microservices are responsible for the persistence of their data. As a result, it can be difficult to maintain data consistency.
• Too big variety. The languages ​​and structures used can be so diverse that maintaining the application becomes difficult. It may be useful to introduce project-wide standards without too much limiting the flexibility of the teams.
• Network overload and lag. Using many small, precise services can increase communication between services. Additionally, if the service dependency chain becomes significantly longer, additional latency may become an issue. Therefore, you should carefully design your APIs.
• Appropriate skills needed and difficult management. Microservices are highly distributed systems. Correlation of logging between services can be an issue. Typically, logging should correlate multiple service invocations for single-user operation. Consider carefully whether your development team has the skills and experience required to work with microservices.

Microservices vs API

These two things often come together. There is nothing strange about it because APIs are an essential part of a microservice architecture. Both concepts are about the structure and interaction of software.  

API is a computing interface which defines interactions between multiple software intermediaries. It defines the kinds of calls or requests that can be made and how to make them. In other words, API is a set of specifically defined methods of communication between different components. Modern APIs adhere to standards, such as HTTP and REST, that are very widely used and accessible. They are more standardized, have a much stronger discipline in terms of security and management, and are monitored and managed for efficiency and scale.

Microservices can be simply misinterpreted as an endpoint providing an API. But microservices have much more flexibility and capabilities than this. Each one of them will have its API. The API sits in front of the microservice and allows various components of this architecture to communicate with each other. Microservices individually can draw from their functions to have a more controllable operation. So it can be briefly summarized that microservices are a whole, complex architecture, and APIs are one of its elements.

Service-oriented architecture vs microservices

We mentioned above that microservices are a variant of service-oriented architecture structural style and therefore have many common characteristics.

Service-oriented architecture (SOA) is a software design style in which services are delivered to other components through a communication protocol over a network. SOA integrates distributed, separately maintained, and deployed software components. It is based on specific core values, many of which also apply to microservices, such as flexibility, business value over technical strategy, evolutionary refinement, or inner interoperability. The same is true of principles: service granularity, autonomy, composability to recall the most valid of them.

The differences start when we talk about the more detailed properties. Let’s take an example of code reuse. In SOA, it’s strongly wanted and even essential at an enterprise level. In a microservices architecture, reusing components results in dependencies that reduce agility and resilience. Microservices are focused on decoupling and prefer to reuse code by copy and data duplication.

When it comes to service granularity, the components of SOA can range from small, specialized to enterprise-wide services. Microservices architectures are made up of specific, specialized services, each of which is designed to do a single job very well.

They also differ in their approach to data storage. SOA involves sharing data between services, and in turn, in microservices architecture, each service can have independent data storage.

SOA simplifies programming and troubleshooting by taking advantage of sharing a common architecture. However, it also causes SOAs to run slower than microservice architectures that gain time from duplication. 

Overall, SOA is a better solution for large and complex business applications. It’s most suitable for environments that require integration with a wide variety of applications.

What are the biggest challenges with microservices?

Before starting a microservices architecture based project, it’s important to know the possible challenges to overcome or sometimes accept.

As the number of services increases, so does the complexity of managing services and maintaining data consistency. Leading a complex project that is structured around multiple programming languages, frameworks and approaches can cause many problems. This may be a particular difficulty for new developers joining the project team. And when the application goes into maintenance mode, teams are reduced and suddenly more people are needed to do all the work through the variety of technology used. 

Complicated development and testing may be an issue in the case of microservices, too. Writing small services based on other dependent services requires a different approach than writing a traditional monolithic or layered application. Not all available tools are designed to work with service dependencies. Besides, each service has operations performed depending on the applied approach. Refactoring across service boundaries can be problematic. Testing service dependencies are also elaborate, especially if the application is changing rapidly. Using microservices effectively requires a mature DevOps methodology then.

Summary

The success of Netflix, which has moved from a monolithic architecture to a cloud-based microservice architecture, encourages many companies to walk this way. Google, Amazon, IBM, and LinkedIn have also done so, and the list is still expanding. It’s a noteworthy solution and its enormous advantages make it a widely used industry standard. As we can see, the winning streak of microservices not only seems to last at the moment but will continue for years.