What are Microservices? The Next Software Architecture

What are Microservices? The Next Software Architecture
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Nearly all computer systems today handle multiple tasks using shared resources. A fundamental question in computer programming revolves around the optimal coupling of the code segments performing these tasks. One effective answer is the microservices architecture, which organizes functionality into discrete, self-contained services that interact to form a comprehensive system.

While the concept of interconnected components is not new, microservices have become particularly well-suited for cloud-based applications. This architecture aligns seamlessly with the DevOps philosophy, promoting rapid and continuous deployment of new features.

This article delves into microservices, outlining the benefits and drawbacks of transitioning to a microservices architecture.

Understanding Microservices

The term "micro" in microservices suggests small applications. However, it is more accurate to view them as services designed to handle specific tasks or solve distinct problems. As Microsoft Azure documentation puts it, "Microservices should be designed around business capabilities, not horizontal layers such as data access or messaging."

Microservices communicate with each other and external users through stable APIs, allowing the internal functionality of a service to be modified without impacting the entire system. By dividing a large application into independently operating pieces, microservices facilitate the creation of CI/CD (continuous integration and continuous delivery) pipelines, essential for DevOps. Moreover, well-defined APIs enhance the ease of automated testing for microservices.

The Microservices Architecture

When discussing microservices, the term microservices architecture often arises. This encompasses not only the microservices themselves but also the supporting infrastructure, including:

  • Automated service management and discovery components, ensuring resilience and failover capabilities.
  • Simple communication routing methods between services.
  • API gateways to manage communication between microservices and external systems.

The primary goal is to build an architecture that is resilient to failure and capable of evolving without needing a complete overhaul.

Microservices vs. Monolithic Architecture

Previously, monolithic architecture was the norm, where an application's code resided in a single large executable file. While monolithic applications are simpler to manage and require less oversight, they are harder to scale and improve compared to microservices. A monolithic application uses one database for all operations, whereas each microservice typically manages its own data, necessitating multiple databases in a microservices architecture.

Defining Microservices

Microservices should focus on specific functionalities, which is easier said than done. Domain analysis and domain-driven design help break down complex tasks into manageable problems solvable by individual microservices. For example, a shipping application might separate accounts and shipping into distinct bounded contexts, each handled by separate microservices.

Microservices vs. SOA and Web Services

Microservices might remind some of service-oriented architecture (SOA) and web services, but there are distinctions:

  • SOA vs. Microservices: SOA involves tightly coupled components often sharing resources and communicating via an enterprise service bus. Microservices, by contrast, are more independent, sharing fewer resources, and communicating through lightweight protocols.
  • Web Services vs. Microservices: Web services are public-facing functionalities accessed via the web, such as Google Maps. Unlike microservices, they do not necessarily connect to other services.

Communication in Microservices

Microservices architecture advocates for "smart endpoints and dumb pipes," favoring simple and well-established communication methods. Typically, communication between microservices is asynchronous, which enhances flexibility and resilience. Synchronous protocols like HTTP can still be used, but asynchronous protocols such as AMQP (Advanced Message Queuing Protocol) are common.

Pros and Cons of Microservices

Benefits:

  1. Rapid Development Lifecycle: Each microservice has its own development and update lifecycle, allowing incremental advancement of the entire application.
  2. Service Isolation: This simplifies maintenance and troubleshooting, allows for language flexibility, and aids in fault isolation.
  3. Scalability: Specific aspects of the application can be scaled independently.
  4. Reusability: Services can be reused across different applications.
  5. Third-Party Integration: Standardized APIs enable easy integration of external services.

Challenges:

  1. Architectural Complexity: Managing a distributed system can be complex, despite orchestration tools like Kubernetes.
  2. Performance Bottlenecks: API-based communication can be slower than internal process communication in a monolithic application.
  3. Difficulty in Separating Concerns: Functional overlap and coordination challenges can arise.
  4. Security Risks: The increased attack surface in a microservices architecture poses additional security challenges.
  5. Cultural Shift: Adopting microservices often requires significant organizational changes, especially for teams not yet familiar with CI/CD and DevOps practices.

Design Patterns for Microservices

Several design patterns address common challenges in microservices:

  • Service Registry: Connects clients to available microservice instances.
  • Circuit Breaker: Prevents repeated calls to failed services.
  • Fallback: Provides alternatives for failed services.
  • Sidecar: Adds auxiliary services for logging, synchronization, or monitoring.
  • Adapter: Normalizes interfaces between the main container and external systems.
  • Ambassador: Facilitates external connections for the main container.

Microservices with Docker and Kubernetes

Containers have propelled microservices into the mainstream. Unlike virtual machines, containers share the host OS kernel while isolating user space, making them lightweight and quick to deploy. Each microservice can run in its container, simplifying management and scalability. Docker is a leading container implementation, often paired with Kubernetes for orchestration.

Microservices on AWS and Azure

Containers are ideal for cloud deployment, leveraging flexible compute resources. Major cloud providers like AWS, Microsoft Azure, and Google Cloud offer robust support for containerized microservices, enhancing efficiency and scalability.

Migrating to Microservices

Transitioning to a microservices architecture involves careful planning, especially when migrating from a monolithic application. The process can be incremental, gradually building microservices to replace parts of the monolithic system. For a detailed guide, refer to resources like InfoWorld's "How to get started with event-driven microservices."

Good luck on your journey to adopting microservices!