Distributed System Design Patterns

Cloud / Distributed System Design Patterns

Circuit Breaker Pattern

classDiagram
    class CircuitBreaker {
      +call(service)
      +trip()
      +reset()
      -state
    }
    class Service {
      +handleRequest()
    }
    CircuitBreaker --> Service : delegates

The Circuit Breaker pattern prevents cascading failures in distributed systems by monitoring remote service calls. If a service call fails repeatedly, the circuit breaker trips to an open state, stopping further calls until the service is deemed healthy again.

API Gateway Pattern

classDiagram
    class APIGateway {
      +routeRequest()
    }
    class Client {
      +sendRequest()
    }
    class MicroserviceA {
      +processRequest()
    }
    class MicroserviceB {
      +processRequest()
    }
    Client --> APIGateway : sends requests
    APIGateway --> MicroserviceA : forwards
    APIGateway --> MicroserviceB : forwards

The API Gateway pattern acts as a single entry point into a system of microservices. It routes client requests to the appropriate backend services, handles authentication, rate limiting, and can perform protocol translation.

Service Discovery Pattern

classDiagram
    class ServiceRegistry {
      +register(service)
      +deregister(service)
      +discover(serviceName)
    }
    class ServiceInstance {
      +serviceID
      +address
    }
    class Client {
      +lookupService()
    }
    ServiceRegistry o-- ServiceInstance : manages
    Client --> ServiceRegistry : queries

The Service Discovery pattern enables dynamic registration and lookup of service instances in a distributed environment. This is critical for systems where services scale up or down and change their network locations frequently.

Event Sourcing Pattern

classDiagram
    class Aggregate {
      +applyEvent(event)
    }
    class EventStore {
      +append(event)
      +getEvents(aggregateId)
    }
    Aggregate --> EventStore : persists events

The Event Sourcing pattern stores all changes to the application state as a sequence of events. The current state is rebuilt by replaying these events, providing a full audit trail and enabling complex event-driven architectures.

CQRS Pattern

classDiagram
    class CommandHandler {
      +handleCommand(command)
    }
    class QueryHandler {
      +handleQuery(query)
    }
    class DataStore {
      +writeData()
      +readData()
    }
    CommandHandler --> DataStore : writes
    QueryHandler --> DataStore : reads

The Command Query Responsibility Segregation (CQRS) pattern separates the write (command) and read (query) operations into different models. This separation can optimize performance, scalability, and security in distributed systems.