# Armeria — Async Microservice Framework for Java and Kotlin

> A high-performance open-source microservice framework by LINE that natively supports gRPC, Thrift, REST, and GraphQL on a single port with built-in observability and service discovery.

## Install

Save in your project root:

# Armeria — Async Microservice Framework for Java and Kotlin

## Quick Use
```java
// build.gradle: implementation "com.linecorp.armeria:armeria:1.31.0"
import com.linecorp.armeria.server.Server;
Server server = Server.builder()
    .http(8080)
    .service("/hello", (ctx, req) -> HttpResponse.of("Hello, Armeria!"))
    .build();
server.start().join();
```

## Introduction
Armeria is an open-source asynchronous HTTP/2 microservice framework developed by LINE Corporation. It allows you to serve and consume gRPC, Thrift, REST, and GraphQL services all on a single server and port, making it well-suited for polyglot microservice architectures on the JVM.

## What Armeria Does
- Serves multiple RPC and REST protocols simultaneously on one port with automatic protocol detection
- Provides a fully asynchronous, non-blocking architecture built on Netty and Java CompletableFuture
- Includes built-in client-side load balancing with DNS, ZooKeeper, and Eureka service discovery
- Offers automatic API documentation via a built-in DocService web UI
- Supports decorators for cross-cutting concerns like logging, metrics, retries, and circuit breakers

## Architecture Overview
Armeria is built on top of Netty and uses HTTP/2 as its primary transport. Incoming requests are demultiplexed based on content type and path to the appropriate protocol handler (gRPC, Thrift, REST, or GraphQL). The decorator pattern allows composable middleware-like behavior for both servers and clients. Thread pools are managed internally with an event loop model, and blocking operations can be offloaded to a configurable executor.

## Self-Hosting & Configuration
- Add the `armeria` dependency via Gradle or Maven to any JVM project
- Use `Server.builder()` to configure services, ports, TLS, and access logs programmatically
- Integrate with Spring Boot via the `armeria-spring-boot3-starter` module
- Configure client-side load balancing with endpoint groups and health-check-based selection
- Enable TLS with `ServerBuilder.tls()` using certificate files or a KeyStore

## Key Features
- Automatic HTTP/1.1 and HTTP/2 protocol negotiation with cleartext (h2c) support
- Built-in DocService that generates interactive API documentation for all registered services
- Request throttling, retries with backoff, and circuit breaker decorators out of the box
- Native Kotlin coroutine support for idiomatic async programming
- Distributed tracing integration with Brave (Zipkin) and Micrometer metrics

## Comparison with Similar Tools
- **Spring WebFlux** — Reactive but HTTP-only; Armeria natively handles gRPC and Thrift alongside REST
- **gRPC-Java** — gRPC-only framework; Armeria serves gRPC and REST on the same port
- **Vert.x** — Polyglot event-driven toolkit; Armeria has stronger RPC protocol support
- **Quarkus** — GraalVM-focused with faster startup; Armeria has richer multi-protocol capabilities
- **Micronaut** — Compile-time DI framework; Armeria focuses more on protocol flexibility and observability

## FAQ
**Q: Can Armeria replace Spring Boot?**
A: Armeria can run standalone or integrate with Spring Boot. For pure microservices needing multi-protocol support, it can replace the embedded Tomcat/Netty in Spring.

**Q: Does it support Kotlin?**
A: Yes. Armeria has first-class Kotlin coroutine support and a Kotlin DSL for server configuration.

**Q: How does the multi-protocol support work?**
A: Armeria uses content-type sniffing and path-based routing to dispatch requests to the correct protocol handler, all over a single HTTP/2 connection.

**Q: Is it production-ready?**
A: Yes. Armeria is used in production at LINE, serving billions of requests daily across their messaging platform.

## Sources
- https://github.com/line/armeria
- https://armeria.dev/

---
Source: https://tokrepo.com/en/workflows/asset-7bf1cab6
Author: AI Open Source