Eclipse Hono is a cloud-native IoT messaging platform that ingests telemetry and events from devices via multiple protocols (MQTT, CoAP, HTTP, AMQP, LoRa, Sigfox) and routes them to northbound applications over AMQP, Kafka, or Google Pub/Sub. The codebase is modular, comprising protocol adapters, device registry services (JDBC and MongoDB), authentication, command routing, and client libraries. It is built on Vert.x and Quarkus, uses Micrometer for metrics and OpenTracing/OpenTelemetry for distributed tracing. The system handles device registration, credentials management, tenant configuration, connection limits, and resource governance. It includes a CLI tool for consuming telemetry and a comprehensive integration test suite. The repository is actively maintained with frequent commits and CI pipelines.
Apache ServiceComb Java Chassis is a production-grade microservices SDK for Java, providing a comprehensive framework for building, registering, discovering, and governing distributed services. It supports multiple programming models (Spring MVC, JAX-RS, POJO) and transport protocols (REST over Vert.x/Servlet, custom binary Highway, WebSocket). The architecture is modular: a core engine (SCBEngine, Invocation) orchestrates filter chains for consumer, provider, and edge roles; pluggable service registries (ServiceCenter, Consul, ZooKeeper, Nacos, etcd, lightweight) handle discovery and registration; governance modules (circuit breaker, retry, rate limiting, bulkhead, fault injection) are policy-driven via Resilience4j; and Swagger/OpenAPI generators automatically produce API contracts from Java annotations. Dynamic configuration is supported through multiple sources (config-center, Kie, Apollo, etcd) with priority-based injection and hot-reloading. External dependencies include Spring Boot, Vert.x, Jackson, Guava, Resilience4j, Zipkin, and Micrometer. In production, a typical data flow begins with a consumer invocation (via RestTemplate, Invoker.createProxy, or RpcReference) that passes through a consumer filter chain (load balancing, retry, circuit breaker), then a transport layer (REST or Highway) to the provider, which processes the request through a provider filter chain (rate limiting, validation, business logic) and returns a response. The framework handles service registration at startup, periodic heartbeats, and instance cache updates via discovery events. Edge/gateway services can apply custom authentication and routing filters. The codebase is large (3355 files) but well-organized into modules: core, transports, providers, governance, swagger, service-registry, clients, foundations, and demos. It demonstrates strong engineering practices: extensive use of SPI for extensibility, filter chain pattern for middleware, event bus for decoupled lifecycle events, and priority-based configuration management. However, the sheer number of demo modules and multiple registry implementations introduces maintenance overhead, and some legacy patterns (LegacyPropertyFactory, JMockit in tests) indicate areas of technical drift.
Automation Gateway is a reactive, configuration-driven bridge for industrial protocols (OPC UA, MQTT, PLC4X) that routes real-time process data to multiple time-series databases (InfluxDB, IoTDB, OpenSearch, Cassandra, PostgreSQL, etc.) and exposes it via GraphQL, MQTT, and OPC UA servers. The system runs as a single JVM or GraalVM native binary, orchestrated through YAML configuration files that define driver instances, logger sinks, and server endpoints. Its core architecture is built on Vert.x event bus for internal pub/sub messaging, with abstract base classes (DriverBase, LoggerBase) enabling consistent extension for new protocols or data stores. The gateway does not persist data itself; it acts as a real-time router with configurable buffering and queue reliability (memory-mapped disk queue). Key entry points include `App.kt` for the main application and `GraphQLServer.kt` for the administrative API, which supports JWT authentication, health checks, and dynamic component management. External dependencies include Eclipse Milo (OPC UA), HiveMQ MQTT client, PLC4X, Apache IoTDB Thrift, InfluxDB HTTP client, and various database drivers. The codebase is mature (v1.38) with active development, but carries some technical drift in the form of deprecated features still present in source code and a large set of reflection configurations for GraalVM native-image that require careful maintenance.