Implementing a Netty Cluster Long‑Connection Service with Redis Pub/Sub for Message Forwarding

Background – The company needed to develop its own long‑connection server for a social project’s audio/video features, choosing SpringBoot + Netty within a microservice architecture to ensure high concurrency and reliable connections.

Netty Long‑Connection – Netty, an asynchronous NIO framework, can serve as a long‑connection server using the WebSocket protocol, supporting roughly ten thousand connections per instance. In a cluster, client channels may reside on different nodes, requiring node‑aware message routing.

Technology Options – For inter‑node message forwarding, the team considered Zookeeper, MQ, and Redis. Since MQ and Redis were already in use, they evaluated both: MQ offers high reliability but is heavyweight and asynchronous; Redis provides lightweight, low‑latency, high‑concurrency pub/sub with lower reliability. Given the real‑time nature of live‑stream messages, Redis pub/sub was selected.

Architecture – When the service starts, each node registers itself in Redis and subscribes to a specific channel. After a client connects, the node binds the user’s session to its identifier in Redis. When a message arrives, the node checks if the target user is on the same node; if not, it retrieves the target node’s info from Redis and publishes the message to the appropriate channel, where the target node delivers it to the client.

Implementation Overview – The article includes diagrams (omitted here) and describes the key steps: node registration and listener setup, subscription handling, channel listener processing, and a message‑forwarding sender component.

Conclusion – Using Redis pub/sub with a Netty cluster enables automatic node registration and seamless message forwarding across newly added nodes, offering strong scalability. The author also notes ongoing learning of advanced Redis 5 features for further business scenarios.