Navigating API Gateway Options in .NET Core Microservices: A Deep Dive into YARP and Ocelot
In the evolving landscape of .NET Core microservices, selecting an appropriate API gateway or reverse proxy is fundamental. These tools not only manage routing but also handle authentication, load balancing, and service orchestration, ultimately shaping the scalability and resilience of microservices architectures. Two prominent solutions are YARP (Yet Another Reverse Proxy) and Ocelot, each serving distinct roles within this ecosystem. This article explores the configuration, capabilities, and use cases of both, providing a roadmap for developers and architects in making optimal choices.
YARP and Ocelot at a Glance
YARP—Microsoft’s tailored reverse proxy toolkit—caters to high-performance and scalable microservices architectures. Built with modern .NET Core features, YARP emphasizes high throughput and efficient memory use, making it highly suitable for complex, high-demand systems.
In contrast, Ocelot is a lighter, developer-friendly API gateway crafted specifically for .NET Core environments. Its streamlined setup, focused on routing and middleware, is ideal for less-intensive applications with straightforward traffic requirements and moderate scalability needs.
Configuration Insights and Key Differences
YARP Configuration
YARP’s configuration is notably flexible, offering a high degree of control adaptable to dynamic operational demands. It allows configuration through various mediums, including appsettings.json, environment variables, and inline code.
Key Configuration Features:
• Advanced Routing Rules: Supports complex patterns and rewrites, configurable via JSON or fluent APIs, providing extensive customization for traffic management.
• Load Balancing Strategies: Offers dynamic load balancing with options like Round Robin, Least Requests, and Random, essential for managing high-volume requests.
• Health Checks: Integrated active and passive health checks ensure traffic routes exclusively to healthy instances, enhancing reliability.
Example Configuration Snippet in appsettings.json:

"ReverseProxy": {
"Routes": {
"route1": {
"ClusterId": "cluster1",
"Match": {
"Path": "/api/{**catch-all}"
}
}
},
"Clusters": {
"cluster1": {
"Destinations": {
"destination1": {
"Address": "http://localhost:5000/"
}
}
}
}
}

Ocelot’s configuration is purposefully straightforward, managed through a JSON configuration file that integrates seamlessly with .NET Core’s configuration system. This simplicity makes it an attractive option for microservices novices or projects with limited complexity.
Key Configuration Features:
• Routing: Defined in JSON, enabling intuitive setup for downstream paths, upstream templates, and HTTP methods.
• Middleware Integration: Includes delegating handlers for authentication, caching, and rate-limiting to improve security and performance.
• Service Discovery: Supports dynamic service discovery through registries like Consul, which enables effortless service scaling and management.
Example Configuration Snippet in ocelot.json:

{
"ReRoutes": [
{
"DownstreamPathTemplate": "/api/values",
"UpstreamPathTemplate": "/values",
"UpstreamHttpMethod": ["Get"],
"ServiceName": "valueService"
}
]
}

Real-World Use Cases
YARP Use Cases
YARP shines in enterprise-level scenarios, particularly where managing extensive traffic or complex routing is essential. It’s an ideal choice for high-demand environments requiring sophisticated load balancing, multi-cloud support, and advanced configuration capabilities.
Ocelot Use Cases
Ocelot is well-suited for smaller applications or organizations beginning their transition to microservices. Its straightforward configuration and deployment make it perfect for projects that don’t demand the robustness of YARP but benefit from a manageable and effective API gateway solution.
Conclusion
The decision between YARP and Ocelot ultimately depends on your project’s scale and specific requirements. YARP provides advanced control and scalability for enterprise-grade microservices, while Ocelot offers a lightweight and accessible solution for simpler use cases. Both tools empower developers and architects to enhance the efficiency, security, and maintainability of .NET Core microservices architectures, paving the way for future growth and flexibility.