Microservices are a software development approach where a single application is composed of small, independent components that communicate with each other through well-defined interfaces. This architecture contrasts with traditional monolithic designs, where different functionalities are tightly integrated into a single codebase.
Microservices design patterns are a set of methodologies that provide solutions to recurrent design problems. Think of them as templates that can be used in the creation of microservices applications. These patterns are particularly useful when developing complex applications with a large number of microservices.
The Need for Microservices Design Patterns
Managing a microservices architecture involves a variety of complex challenges that are seldom encountered in traditional monolithic systems. These challenges include:
- Service orchestration: Ensuring that multiple, independent services communicate seamlessly to execute complex business processes.
- Fault tolerance: In a distributed system, a failure in one service shouldn’t lead to a system-wide collapse.
- Data consistency: Unlike monolithic systems where you can rely on ACID transactions in a single database, microservices often have their own databases, making transactional consistency a big concern.
- Service discoverability: How services locate each other in a dynamically scaling environment.
To address these challenges systematically, developers can leverage microservices design patterns. These are tested solutions that serve as templates for solving recurring design problems. They guide development teams towards best practices in microservices development, and provide structures that make it easier to create complex but stable systems.
Top 10 Design Patterns in Microservices Architecture
There are numerous microservices design patterns that you can use, each with their unique advantages and use cases. Here are some of the more important patterns:
1. Service Registry
A service registry is like a map for your services; it keeps track of all the services in your system, making it easier for them to find each other.
Every service in your system needs to register itself with the service registry when it starts up, and deregister when it shuts down. Other services can then query the service registry to locate the services they need to interact with. This allows your system to be dynamic and adaptable, as services can come and go as required without disrupting the overall functionality.
2. Circuit Breaker
A circuit breaker is used to detect failures and encapsulate the logic of preventing a failure from constantly recurring. Circuit breakers could be triggered due to bugs in one or more microservices, temporary external system failure, or unexpected operating conditions.
In a microservices architecture, you employ the circuit breaker pattern to monitor the interaction between services. If a service is failing or responding slowly, the circuit breaker trips and prevents further calls to the service, thus preventing a system-wide failure. Once the service is back up, the circuit breaker resets, and things go back to normal.
3. API Gateway
An API gateway acts as a single entry point into your system for all clients. This can be especially beneficial if you have multiple client apps, such as a web app and a mobile app, as it allows you to maintain a single API for all clients, simplifying client-side code.
The API gateway can handle requests in one of two ways. It could route requests to the appropriate services directly, or it could use a process known as composition, where it would combine data from multiple services and return the aggregate result to the client. This not only simplifies client-side code but also makes your system more efficient and user-friendly.
4. Event-Driven Architecture
In an event-driven architecture, when a service performs an action that other services need to know about, it emits an event—a record of the action. Other services then react to the event as necessary. This is a powerful way to decouple services and allows for highly scalable and robust systems.
This architecture allows you to build systems that are more resilient to failure, as the services do not need to be aware of each other. If one service fails, it does not affect the others. Additionally, this architecture allows for high scalability, as you can add new services to the system without affecting existing ones.
5. Database per Service
In a traditional monolithic application, you would have a single database that all services interact with. However, in a microservices architecture, each service has its own database.
Why is this beneficial? Well, it allows each service to be decoupled from the others, which means that a failure in one service does not affect the others. Furthermore, it allows for better performance, as each service can be optimized independently based on its specific needs.
6. Command Query Responsibility Segregation (CQRS)
CQRS is a microservices design pattern that separates read and write operations. In traditional systems, the same data model is often used for both these operations. However, CQRS advocates for a different approach. It proposes the use of separate models for update (Command) and read (Query) operations. This segregation enables you to optimize each model for its specific purpose, thereby improving performance and scalability.
However, implementing CQRS is not without its challenges. It can complicate your system due to the need to synchronize two data models. But, when applied correctly, it can significantly enhance the flexibility and performance of your system.
7. Externalized Configuration
The externalized configuration pattern advocates for the separation of configuration from the code. This separation allows you to modify the behavior of your application without the need for code changes or system restarts.
This pattern is particularly useful in microservices architectures where you may have multiple instances of a service running with different configurations. By externalizing the configuration, you can manage all instances efficiently. However, it does require a robust configuration management system to avoid configuration drift.
8. Saga Pattern
The saga pattern is used to ensure data consistency across multiple services in a microservices architecture. In traditional monolithic systems, transactions are usually managed using a two-phase commit. However, in a microservices architecture, where services are loosely coupled and distributed, this approach is not practical.
The saga pattern proposes an alternative solution. It suggests breaking a transaction into multiple local transactions. Each local transaction updates data within a single service and publishes an event. Other services listen to these events and perform their local transactions. If a local transaction fails, compensating transactions are executed to undo the changes.
9. Bulkhead Pattern
The bulkhead pattern is a microservices design pattern that helps to prevent failures in one part of a system from cascading to other parts. It does so by isolating elements of an application into pools so that if one fails, the others continue to function.
This pattern is inspired by the bulkheads in a ship. Just as a ship is divided into watertight compartments to prevent it from sinking if one part is breached, an application can be divided into isolated groups to protect it from failures.
10. Backends for Frontends (BFF)
The BFF pattern proposes the creation of separate backend services for different types of clients (like desktop, mobile, etc.). This allows you to tailor the backend services to the specific needs of each client, thereby improving user experience and performance.
However, this pattern can lead to code duplication if not managed properly. Therefore, it is crucial to strike a balance between customization and code reuse when using the BFF pattern.
Learn more in our detailed guide to microservices architecture
How to Choose Design Patterns in Microservices
Choosing the right design patterns for your microservices architecture is critical for building a robust and scalable system. Here are a few factors to consider while making your choice.
- Assess service interdependencies: If your services are highly interdependent, a transactional pattern like the saga pattern might be beneficial. On the other hand, if your services are more isolated, patterns like bulkhead can help prevent cascading failures.
- Evaluate resilience requirements: Different patterns offer different levels of resilience. For instance, the bulkhead pattern can improve resilience by preventing failures from cascading. Evaluate how crucial resilience is for your system and choose patterns accordingly.
- Consider security implications: Some patterns may have security implications. For example, the externalized configuration pattern requires a secure configuration management system to protect sensitive configuration information.
- Reusability and future-proofing: Design patterns like backends for frontends can enhance reusability by allowing you to tailor backends for different clients. Meanwhile, patterns like CQRS can future-proof your system by providing flexibility and scalability.
Microservices Delivery with Codefresh
The Codefresh Software Delivery Platform helps you answer important questions within your organization, whether you’re a developer or a product manager:
- What features are deployed right now in any of your environments?
- What features are waiting in Staging?
- What features were deployed on a certain day or during a certain period?
- Where is a specific feature or version in our environment chain?
With Codefresh, you can answer all of these questions by viewing one dashboard, our Applications Dashboard that can help you visualize an entire microservices application in one glance:
The dashboard lets you view the following information in one place:
- Services affected by each deployment
- The current state of Kubernetes components
- Deployment history and log of who deployed what and when and the pull request or Jira ticket associated with each deployment