Breaking Down the Monolith: The Containerization Journey of Transforming Monolithic Applications Into Microservices

This is an article from DZone's 2023 Containers Trend Report.

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Conventionally, software applications were developed using a monolithic architecture where all application components were tightly interwoven and deployed as a single unit. As software applications became more intricate and organizations started relying on distributed systems, the constraints of monolithic architecture started becoming more evident. 

Containerization was introduced as a solution to this and the growing demand for application scalability, agility, and resilience. The success of microservices further propelled the use of containers, which enabled organizations to break down monolithic applications into independently deployable services. This loosely coupled framework also enabled developers to deploy changes quickly, while achieving enhanced scalability and fault tolerance. 

In this article, we explore the limitations of monolithic architecture and demonstrate how containers and microservices can support modern application delivery. We also delve into the various strategies, stages, and key steps organizations can adopt in their journey towards containerization and learn how different strategies can support different use cases.

Breaking a Monolith Into Microservices

Compared to monolithic architecture, a microservices architecture comprises modular, loosely coupled components that communicate via well-defined APIs. This architecture promotes fault tolerance, as the failure of one service has limited impact on the overall system. Microservices also differ from monoliths by using polyglot persistence, which enables each service to select its ideal storage solution based on its requirements. 

However, before you transition from monolithic to microservices architecture, it's essential to understand the key differences between the two for making informed decisions about application design and choosing the right transformation strategy. 

The following table outlines these distinctions, offering insights into the unique benefits and characteristics of each approach: 

Strategies for Migrating to Containers

Strategies for migrating to containers vary depending on an organization's specific requirements and goals. These strategies help manage the transition from monolithic architectures to containerized microservices, allowing organizations to achieve increased agility, scalability, and resilience. Let's review some common approaches. 

Phased Approach

This approach involves incrementally breaking down monoliths into microservices through containerization, beginning with components that will potentially realize maximum benefits first. It reduces risks while giving teams time to learn and adapt processes over time. 

When to use: The phased approach is considered best when you wish to minimize risk and disrupt ongoing operations. It is also suitable for organizations with limited resources or complex monolithic applications who would prefer a gradual transformation from monolithic to microservices.

Hybrid Architecture

The hybrid architecture approach combines monolithic and microservices components, where some remain within monolithic architecture while others migrate toward microservices architectures progressively. This approach balances the benefits of both architectures and is suitable for organizations that cannot fully commit to a complete migration. 

When to use: Adopt this approach when it isn't feasible or necessary to completely transition an application over to microservices. This strategy works especially well for organizations that wish to retain parts of a monolithic application while reaping some advantages of microservices for specific components.

Big Bang Approach

Redesign and implement an entire application using microservices from scratch. Although this strategy might require dedicated resources and may introduce greater risk, this allows organizations to fully exploit the advantages of microservices and containers. 

When to use: Choose this approach when your monolithic application has reached a point where a complete overhaul is necessary to meet current and future demands, or when your organization can afford a resource-intensive yet riskier transition to microservices and containers while reaping all their advantages.

Re-Platforming

This approach involves moving the monolithic application to a container platform without breaking it into microservices. Replatforming offers some benefits of containerization, such as improved deployment and scalability, without the complexities of a full migration to microservices. 

When to use: It's recommended to use re-platforming when the goal is to gain some of the advantages of containerization without breaking down the monolith into microservices. It is also ideal for organizations that are new to containerization and want to test the waters before committing to a full migration to microservices. 

Practical Steps to Embracing a Containerization Journey

Embarking on a containerization journey signifies the transformation of monolithic architectures into streamlined, efficient, and scalable microservices. The following section explores various stages involved in migrating monoliths to containers, and it provides a comprehensive roadmap to successfully navigate the complexities of containerization. 

Stages of Migrating Monoliths to Containers

The migration process from monoliths to containers typically goes through three stages. Each stage focuses on addressing specific challenges and gradually transforming the architecture to optimize efficiency, flexibility, and maintainability: 

1. Identify the monolith in an organization's application architecture. Look for large, tightly coupled systems that have a single codebase, shared resources, and limited modularity. Analyze the dependencies, data flow, and communication patterns to understand the complexities of your monolith.
2. Define service boundaries. Perform domain-driven design (DDD) analysis to identify logical service boundaries within the monolith. Establish bounded contexts that encapsulate specific business functions or processes, enabling microservices to be designed around these contexts and reducing inter-service dependencies.
3. Re-architect the application into smaller, more manageable pieces. Re-architect the monolithic application into microservices using patterns like API gateway, service registry, and circuit breaker. Implement an API-driven approach, with each microservice exposing a RESTful API or using message-based communication such as AMQP or Kafka. 

Figure 1: Migrating monoliths to containers 

Key Steps of a Containerization Journey

Embracing containerization often involves a series of well-defined steps that may be tailored for individual use cases. Successful containerization adoption may vary based on each organization's use case; however, the following four steps provide general guidance as organizations navigate their container journey from identifying component applications and setting up robust management to administering security practices for containers. 

Identify Application Components

Analyze your application's architecture using dependency graphs or architecture diagrams to identify individual components like databases, web servers, and background workers. Determine the components that can be containerized and identify related dependencies that should be resolved during containerization. 

Purpose:

• Provides clarity on the application's architecture
• Helps with efficient resource allocation
• Enables component isolation for greater modularity 
• Helps with dependency management 
• Ensures seamless communication between containerized components 

Containerize Application Components

Create Dockerfiles for each component to enable the encapsulation of application components into isolated containers, which facilitates easier deployment, portability, and version control. Use multi-stage builds to optimize image sizes and employ best practices like using non-root users and minimizing the attack surface. Ensure proper versioning of images by tagging them and storing them in a container registry like Docker Hub, RedHat Quay, or GitHub Container registry. 

Purpose:

• Encapsulates components in containers to create isolated environments
• Enables easy transfer of components across different environments
• Facilitates better version control of components

Container Orchestration

Choose a container orchestration platform such as Kubernetes or Docker Swarm to manage the deployment, scaling, and management of containerized applications. Implement appropriate resource allocation by defining resource limits and requests in your deployment manifests or compose files. Create self-healing deployments using liveness and readiness probes to monitor container health and restart unhealthy containers. 

Purpose:

• Ensures optimal allocation of resources for each container
• Maintains high availability and fault tolerance of applications
• Facilitates rolling updates and rollbacks with minimal downtime

Container Management and Security

Use tools like Prometheus and Grafana for monitoring and logging, with custom alerts for critical events. Implement a CI/CD pipeline for container updates, automating the build, test, and deployment process. Employ security best practices such as scanning images for vulnerabilities, enforcing network segmentation, and applying the principle of least privilege. Additionally, it is also recommended to use container security solutions that help with the continuous monitoring of threats and enforce security policies. 

For instance, the following configuration file can be considered as a pseudocode for managing and securing containers: 

# Example of container security best practices configuration
container_security:
  - use_non_root_user: true
  - minimize_attack_surface: true
  - implement_network_segmentation: true
  - enforce_least_privilege: true 

As the next step, the following pseudocode, for instance, illustrates how to load the security best practices configuration and apply it to running containers using any container management tool: 

# Pseudocode to manage and secure containers
import container_management_tool

# Load security best practices configuration
security_config = load_config("container_security")

# Apply security best practices to running containers
container_management_tool.apply_security_config(security_config)

# Monitor container performance and resource usage
container_management_tool.monitor_containers()

# Implement logging and alerting
container_management_tool.setup_logging_and_alerts() 

Purpose:

• Monitors container performance and resource usage
• Implements logging and alerting for better visibility into containerized applications
• Ensures container security by scanning images for vulnerabilities and applying best practices
• Enforces security policies and monitors threats using container security solutions

Real-World Use Cases

Some real-world examples of organizations that have successfully implemented containerization in their application architecture include Netflix, Spotify, and Uber. 

Netflix: Architecture Transformation for Agility and Scalability

Netflix is one such company that has successfully leveraged containers and microservices architecture to address the massive scale of its streaming service. By investing in container-based workloads, Netflix was able to break down their monolithic app into separate, more focused services that could be deployed and managed independently, giving greater agility and scalability while accommodating large traffic spikes during peak times more easily. This provided greater flexibility as they handled increased traffic with greater ease.

Spotify: Containerization for Better Developer Productivity

Spotify also embraced containers and microservices to increase developer productivity. Before the transformation journey, they relied on a monolithic architecture that required extensive coordination among cross-functional teams to run and maintain. By breaking up this monolith with containerization and microservices, they created a modular architecture where developers were able to work independently on specific components or features of their application without interference from one team to the next. Containers also provided a consistent environment in which developers were able to build, test, and deploy iterative changes on application easily. 

Uber: Containers for Deployments and Traffic Spike Management

At first, Uber was using a monolithic framework that was difficult to scale and required close team collaboration in order to function smoothly. They transitioned over to using Domain-Oriented Microservice Architecture (DOMA) for scaling their services based on demand. This platform utilized containers, which allowed more rapid deployment and improved the handling of traffic spikes. 

Uber took advantage of microservices and containers to scale its services independently, enabling it to adapt their offerings according to traffic or usage patterns. In addition, using microservices provided increased fault isolation and resilience that ensured its core services remained available even if one service failed. 

Conclusion

Embarking on a containerization journey enables organizations to transform their monolithic applications into more agile, scalable, and resilient microservices-based systems. Despite the benefits, it's also essential to acknowledge that transitioning from monolithic applications to containerized microservices may introduce challenges, such as increased operational complexity and potential issues in managing distributed systems. 

As you reflect on your own organization's containerization journey, consider the following questions: 

• Which components of your monolithic application will benefit the most from containerization?
• What strategy will you adopt for migrating to containers: phased approach, hybrid architecture, big bang approach, or re-platforming?
• How will you ensure effective container orchestration and management in your new architecture?

With the above questions answered, the blueprint of the transformation journey is already defined. What comes next is implementing the chosen strategy, monitoring the progress, and iterating as needed to refine the process.

This is an article from DZone's 2023 Containers Trend Report.

For more:

Read the Report