Introduction

In this blog post, we will explore the process of decomposing a monolithic application into microservices and the benefits it brings. We will discuss various strategies, best practices, and patterns involved in this architectural transformation.

Benefits of Decomposing Monoliths

  • Scalability: Microservices enable individual components to scale independently, allowing you to allocate resources efficiently based on specific needs.
  • Agility and Faster Time-to-Market: Microservices enable teams to work independently, allowing for parallel development and deployment cycles, leading to quicker feature delivery.
  • Improved Maintainability: Smaller, focused microservices are easier to understand, modify, and maintain compared to complex monolithic codebases.
  • Fault Isolation and Resilience: In a microservices architecture, if one service fails, it doesn’t affect the entire system, ensuring fault isolation and improved system resilience.
  • Technology Heterogeneity: Microservices allow you to use different technologies and frameworks that are best suited for each service’s requirements, promoting innovation and flexibility.
  • Team Scalability: Microservices facilitate team autonomy, allowing smaller teams to work on specific services, enabling scalability and faster development cycles.
  • Improved Fault Tolerance: With the decoupled nature of microservices, failures in one service are less likely to cascade to other parts of the system.
  • Continuous Deployment: Microservices align well with continuous integration and deployment practices, enabling frequent and independent releases of services.
  • Enhances System Stability: Microservices reduce the impact of changes by isolating them within smaller codebases, making it easier to identify and fix issues.
  • Simplified Technology Stack: Microservices enable you to choose the most appropriate technology stack for each service, resulting in simplified development and maintenance.
  • Division of labor and knowledge
  • Loose coupling of interactions

Obstacles to Decomposing an Application into Services

  • Legacy dependencies: Discuss challenges related to dependencies on legacy code, databases, or external systems and strategies to overcome them.
  • Shared state and data: Explain the difficulties in decomposing monolithic applications that rely on shared state and data and approaches to handle them.
  • Coupling and interdependencies: Discuss the issues caused by tight coupling and interdependencies between components and how to identify and address them.
  • Organizational resistance: Explore the challenges of organizational resistance to change and strategies to gain buy-in and support for the microservices initiative.
  • Network latency
  • Reduced availability due to synchronous communication
  • Maintaining data consistency across services
  • Obtaining a consistent view of the data
  • God classes preventing decomposition

Monolith Decomposition Strategies

  • Strangler Fig pattern: Explain how to gradually replace components of the monolith with microservices, ensuring seamless migration and minimizing disruption.
  • Branch by Abstraction: Discuss the approach of creating an abstraction layer to gradually introduce microservices while maintaining the existing monolith.
  • Parallel Runway: Explore the concept of building new microservices alongside the monolith, enabling a phased migration.

Creating the Architecture of the Target Service

When designing the architecture of a target microservice, consider the following:

  • Service boundaries: Define clear boundaries for the microservice, ensuring it has a single responsibility and can be independently developed and deployed.
  • API design: Design a well-defined and versioned API that exposes the functionality of the microservice.
  • Scalability: Implement scalability mechanisms like load balancing and horizontal scaling to handle increased demand.

Service Communication and Integration

  • Synchronous vs. asynchronous communication: Discuss the pros and cons of different communication styles and when to use each approach.
  • Event-driven architectures: Explain the benefits of using events for loose coupling and scalability in a microservices ecosystem.
  • Message brokers: Explore the use of message brokers like Apache Kafka or RabbitMQ for reliable and decoupled communication between services.

Data Management in Microservices

  • Database per service: Discuss the advantages of having a dedicated database for each microservice to ensure loose coupling and independent evolution.
  • Eventual consistency: Explain the concept of eventual consistency and techniques like distributed transactions or compensating transactions.
  • Data replication: Discuss strategies for replicating data across microservices and maintaining data integrity.

Testing and Deployment Strategies

  • Unit testing: Describe how to write comprehensive unit tests for individual microservices to ensure their correctness and functionality.
  • Continuous integration/continuous deployment (CI/CD): Discuss the importance of automation in the deployment process and how to set up CI/CD pipelines for microservices.
  • Versioning and rollbacks

View Model of Architecture

Logical View Implementation View Process View Deployment View
❓ What developers create What is produced by the build system Running components Processes running on machines
Elements Classes, packages modules, jars, wars Processes Machines and Processes
Relations Relationship between them Their dependencies Inter Process communication Networking

What is a service ❓

✋ A service is a standalone, independently deployable software component that implements some useful functionality.

👉 A service has an API that encapsulates the implementation. The API defines operations, which are invoked by clients. There are two types of operations: commands update data, and queries retrieve data. When its data changes, a service publishes events that clients can subscribe to.

Identifying the system operations Creating a high-level domain model Defining system operations - command and queries

Defining services by applying the Decompose by business capability pattern Business capabilities define what an organization does Identifying business capabilities From business capabilities to services

Decomposition guidelines Single Responsibility Principle The other useful principle is the Common Closure Principle: