Architecture Overview

Architecture Overview

This document outlines the technical architecture for a robust, scalable microservice-based application. The architecture leverages modern technologies for containerization, service discovery, message queuing, secret management, service communication, monitoring, caching, object storage, high-performance database, API gateway, and service mesh capabilities.

High-Level Architecture

The architecture follows modern microservices best practices with clear separation of concerns:

1. Edge Layer: Traefik serves as the API gateway, handling incoming requests, routing, and security
2. Service Discovery: Consul provides the foundation for service registration and discovery
3. Secret Management: HashiCorp Vault secures sensitive credentials and secrets
4. Service Mesh: Linkerd provides advanced service-to-service communication patterns
5. Microservices: Individual containerized services that perform specific business functions

Request Flow

1. Client Request: A client makes an HTTP/HTTPS request to the system.
2. Traefik Processing:
   • The request hits Traefik, which acts as the API gateway and entry point.
   • Traefik has already loaded routing rules and middleware configurations from Consul.
   • Traefik applies configured middlewares (rate limiting, authentication, etc.) directly to the request.
3. Request Forwarding: After middleware processing, Traefik forwards the request to the appropriate microservice based on routing rules.
4. Service Response: The microservice processes the request and returns a response.
5. Response Delivery: Traefik forwards the response back to the client, potentially applying response middlewares.

Service Registration Flow

1. Service Startup: When a microservice starts, it registers itself with Consul either:
   • Automatically via Docker labels (for containerized services)
   • Programmatically via Consul API (for services implementing direct registration)
2. Health Checks: Consul performs regular health checks to ensure the service is operational.
3. Service Discovery: Traefik and other services discover services through Consul's catalog or KV store.

Service-to-Service Communication

1. Service Discovery: Microservice A queries Consul to discover the location of Microservice B.
2. Direct Communication: After discovery, Microservice A communicates directly with Microservice B.
3. Communication Methods:
   • REST/HTTP calls between services
   • gRPC for more efficient service-to-service communication
   • Event-based communication via message brokers (e.g., RabbitMQ)

Services do not communicate through Consul itself; they use Consul only to discover where other services are located. The actual communication happens directly between services.

Configuration Flow

1. Infrastructure Setup: When the infrastructure starts, middleware configurations are registered in Consul KV store.
2. Traefik Configuration:
   • Traefik loads initial configurations from Consul.
   • Traefik watches for changes to configurations in Consul and updates dynamically.
3. Middleware Application:
   • Middlewares are configured in Consul and applied by Traefik during request processing.
   • Microservices reference these middlewares using labels or tags.
   • The actual middleware logic executes within Traefik, not as separate services.

Secret Management Flow

1. Vault Initialization: On first startup, Vault is initialized and unsealed with encryption keys securely stored.
2. Secret Loading: Predefined secrets are loaded into Vault's key-value store.
3. Service Authentication: Microservices authenticate to Vault using the AppRole method.
4. Secret Access:
   • Services request specific secrets they need from Vault.
   • Vault checks policies to ensure the service has appropriate access rights.
   • If approved, Vault provides the requested secrets to the service.
5. Secret Rotation: Credentials can be automatically rotated without service disruption.

Architecture Diagram

A high-level architecture diagram should be created to illustrate the interaction between these components, showing:

• Container orchestration layer
• Traefik API gateway at the edge
• Linkerd service mesh for service-to-service communication
• Service discovery with Consul
• Message flow through RabbitMQ
• Redis caching layer
• ScyllaDB persistence layer
• MinIO object storage
• Secret management with Vault
• Monitoring with Prometheus

Components Overview

The architecture leverages the following key technologies:

Component	Technology	Purpose
Containerization	Docker	Application containerization
Orchestration	Docker Compose	Multi-container orchestration
Service Discovery	Consul	Service discovery and distributed configuration
API Gateway	Traefik	Edge router and API gateway
Service Mesh	Linkerd	Transparent service mesh
Message Queue	RabbitMQ	Asynchronous communication
Secret Management	HashiCorp Vault	Secure secret storage and management
Service Communication	gRPC	Efficient inter-service communication
Monitoring	Prometheus, Logstash, Jaeger	Metrics, logs, and tracing
Caching	Redis	In-memory data structure store
Object Storage	MinIO	S3-compatible object storage
Database	ScyllaDB	High-performance NoSQL database

For detailed information about each component, see the Core Components page.