构建 WebSocket 在线状态服务器

项目概述

本项目实现一个面向 real-time presence 的完整系统，核心要解决的问题是 broadcasting presence updates to room members while keeping per-connection memory bounded under backpressure。整体由 Connection registry、Room router、Presence tracker、Message history、Backpressure guard 五个模块组成，每个模块单一职责、可独立测试，最后通过集成测试验证端到端正确性。设计上把 a slow client whose send buffer fills and blocks the broadcast loop for the whole room 作为第一类需求先行处理，而非事后再补。

架构与关键决策

数据模型为 a map of rooms to member connection sets, with a ring buffer of recent messages per room for replay on join。Connection registry 定义其余阶段共同依赖的数据形状并在边界处校验输入；Room router 承载 real-time presence 的正确性逻辑；Presence tracker 专门处理 a slow client whose send buffer fills and blocks the broadcast loop for the whole room，在失败路径上给出明确的拒绝、重试或降级策略；Message history 提供可观测性，每次操作输出带关联 id 的结构化事件；Backpressure guard 在过载时按既定方式降级，避免过载演变为数据损坏。配置与代码分离，使风险变更可经 diff 审阅。

实施与测试

按五个阶段依次实现 Connection registry、Room router、Presence tracker、Message history、Backpressure guard，每阶段配套聚焦单测。集成测试组合各模块并驱动真实 real-time presence 场景：先验证正常路径，再刻意触发 a slow client whose send buffer fills and blocks the broadcast loop for the whole room 并断言系统降级而非损坏。所有依赖均在进程内或被桩替换，用例在 CI 中确定可复现。

限制与后续

• 单区域设计，多区域复制超出范围。
• Connection registry 默认进程内，未水平共享。
• 无鉴权层，假定部署在强制身份的边缘之后。

代码示例

# setup for websocket-presence-server
pnpm init
pnpm add ws pino
pnpm add -D typescript tsx vitest

websocket_presence_server/
├── src/index.ts
├── src/connection-registry.ts
├── src/room-router.ts
├── tests/websocket_presence_server.test.ts
└── package.json

// Connection registry: real-time presence core
export function connectionregistry(input: ConnectionregistryInput): ConnectionregistryResult {
  // Build the connection registry that anchors real-time presence and defines the core data shape.
  return processConnectionregistry(input);
}

// Room router — handles real-time presence Add the room router so
export class Roomrouter {
  constructor(private opts: RoomrouterOptions) {}
  async run(ctx: Context): Promise<RoomrouterOutput> {
    return this.execute(ctx);
  }
}

// Presence tracker: real-time presence stage
export const presencetracker = (next: Next) => async (req: Request) => {
  const out = await transform(req);
  return next(out);
};

// Message history for real-time presence
export async function messagehistory(stream: AsyncIterable<Chunk>): Promise<Aggregate> {
  let acc = init();
  for await (const c of stream) acc = merge(acc, c);
  return acc;
}

// Backpressure guard: real-time presence finalization
export function backpressureguard(state: State): Result {
  validate(state);
  return finalize(state);
}

# run the real-time presence test suite
pnpm vitest run