spring-cloud-starter-gateway-server-webflux vs spring-cloud-starter-gateway-server-webmvc

 The difference between spring-cloud-starter-gateway-server-webflux and spring-cloud-starter-gateway-server-webmvc lies in their underlying technology stack, concurrency model, and official support in Spring Cloud Gateway. Here's a breakdown:

1. spring-cloud-starter-gateway-server-webflux (Reactive/WebFlux)

• Technology Stack:
  Built on Spring WebFlux (reactive stack) and Project Reactor.

• Concurrency Model:
  Uses non-blocking I/O (event-loop) for high scalability and efficiency with concurrent requests.

• Dependencies:
  Includes spring-boot-starter-webflux (reactive Netty, Undertow, etc.).

• Performance:
  Optimized for high-throughput, low-latency scenarios (e.g., microservices, streaming).

• Official Support:
  This is the standard/officially supported starter for Spring Cloud Gateway.

• Use Case:
  Reactive applications, cloud-native microservices requiring scalability.

2. spring-cloud-starter-gateway-server-webmvc (Blocking/WebMVC)

• Technology Stack:
  Built on Spring WebMVC (servlet stack) with blocking I/O.

• Concurrency Model:
  Uses thread-per-request (blocking) model, limiting scalability under heavy load.

• Dependencies:
  Includes spring-boot-starter-web (Tomcat, Jetty, etc.).

• Performance:
  May bottleneck under high concurrency due to thread overhead.

• Official Support:
  Not officially supported or maintained by Spring Cloud.
  Likely a community experiment or deprecated prototype.

• Use Case:
  Only for legacy servlet applications (not recommended for new projects).

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Key Technical Differences:

Aspect	webflux (Reactive)	webmvc (Blocking)
HTTP Server	Netty, Reactor-based servers	Tomcat, Jetty (Servlet containers)
Request Handling	Asynchronous (event-loop)	Synchronous (thread-per-request)
Scalability	High (efficient resource usage)	Limited (thread exhaustion risk)
Backpressure Support	Yes (via Project Reactor)	No
Reactive Streams	Full support (Mono/Flux)	Not applicable

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Why Spring Officially Recommends WebFlux:

1. Gateway Design:
   Spring Cloud Gateway relies on reactive APIs (e.g., ServerWebExchange, Reactor).

2. Compatibility:
   Integrates seamlessly with reactive Spring projects (Spring Data R2DBC, RSocket).

3. Performance:
   Non-blocking I/O handles 10K+ concurrent connections with minimal threads.

4. Future-Proof:
   Aligns with cloud-native/async trends (gRPC, WebSocket, streaming).

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Should You Use webmvc?

• Avoid it.
  The webmvc variant is unsupported, may have bugs, and negates the core benefits of Spring Cloud Gateway (scalability, non-blocking).

• If you need a blocking API gateway, consider alternatives:

  • Spring Cloud Netflix Zuul (deprecated but servlet-based).

  • Traditional reverse proxies (Nginx, HAProxy).

Correct Starter for New Projects:

Use the standard (and only officially maintained) dependency:

xml

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<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-gateway</artifactId> <!-- Implicitly uses WebFlux -->
</dependency>

This automatically pulls spring-cloud-starter-gateway-server-webflux under the hood.

Summary:

• webflux: Production-ready, reactive, high-performance.

• webmvc: Experimental/legacy, blocking, unsupported.
  Always choose spring-cloud-starter-gateway (WebFlux) for new work.