Server-sent events

约 1886 字大约 6 分钟

2025-01-07

EventSource

简介

SSE（Server-Sent Events）是一种基于 HTTP 协议，用于实现服务器主动向客户端推送数据的技术。它在客户端与服务器之间建立一条持久化连接，并通过这条连接实现服务器向客户端的实时数据推送，而客户端不能发送数据给服务端

特点

单向通信
实时推送
轻量级
支持跨域、使用简单、支持自动重连

适合场景

数据大屏
消息推送
股票交易
在线聊天

最致命缺点：无法携带自定义请求头Header，只支持Get请求；

简单使用

// 创建 EventSource 实例
const evtSource = new EventSource("http://localhost:3000/events");

// 监听消息
evtSource.onmessage = function (event) {
  console.log("接收到的消息：", event);
};

// 监听连接打开
evtSource.onopen = function () {
  console.log("连接已建立");
};

// 监听错误
evtSource.onerror = function (err) {
  console.error("EventSource 发生错误:", err);
};

🔥SSE.JS

简介

sse.js 是 JavaScript 的灵活 EventSource 替代品（完全兼容的 EventSource polyfill），旨在使用服务器发送事件（SSE）流，比标准 EventSource 具有更多的控制和配置。

特点

支持自定义Header
支持POST请求类型

GIthub：sse.js

食用文档

安装

npm install sse.js

用法

import { SSE } from "sse.js";

// 创建 SSE 实例
var source = new SSE("http://192.168.7.165:3000/events", {
  headers: {
    "X-App": "MyApp",
    "X-Token": "my-custom-token",
  },
});

// 监听消息
source.onmessage = function (event) {
  console.log("接收到的消息：", event);
};

// 监听连接打开
source.onopen = function () {
  console.log("SSE 连接已建立");
};

// 监听错误
source.onerror = function (err) {
  console.error("EventSource 发生错误:", err);
};

FetchEventSource

简介

FetchEventSource 提供了更多的灵活性和定制能力，能够实现如自动重试、身份验证、自定义事件处理等复杂功能

特点

支持自定义Header

GIthub：FetchEventSource

食用文档

安装

npm install @microsoft/fetch-event-source

用法

import { fetchEventSource } from "@microsoft/fetch-event-source";

fetchEventSource("http://192.168.7.165:3000/events", {
  headers: {
    "X-App": "MyApp",
    "X-Token": "my-custom-token",
  },
  onmessage(event) {
    console.log("接收到的消息：", event);
  },
});

EventSourcePolyfill

简介

EventSourcePolyfill是一个用于实现 Server-Sent Events (SSE) 的 polyfill 库；

提供了对不支持原生 EventSource 接口的浏览器的支持，使得开发者可以在所有现代浏览器中使用 SSE 技术。

特点

支持低版本浏览器
支持自定义Header

GIthub：EventSourcePolyfill

食用文档

// 创建 EventSourcePolyfill 实例
const evtSource = new EventSourcePolyfill("http://192.168.7.165:3000/events", {
  headers: {
    "X-App": "MyApp",
    "X-Token": "my-custom-token",
  },
});

// 监听消息
evtSource.onmessage = function (event) {
  console.log("接收到的消息：", event);
};

// 监听连接打开
evtSource.onopen = function () {
  console.log("SSE 连接已建立");
};

// 监听错误
evtSource.onerror = function (err) {
  console.error("EventSource 发生错误:", err);
};

ModernEventSource-自定义实现

实现

JavaScript

/**
 * 默认事件解析器类
 * @class
 */
class DefaultEventParser {
  /**
   * 解析事件字符串
   * @param {string} eventString - 要解析的事件字符串
   * @returns {string|null} 解析后的数据，如果没有有效数据则返回 null
   */
  parse(eventString) {
    const lines = eventString
      .split("\n")
      .map((line) => line.trim())
      .filter(Boolean);
    return lines.length > 0 ? lines.join("\n") : null;
  }
}

/**
 * 自定义事件源类，用于处理服务器发送事件（SSE）
 * @class
 */
class CustomEventSource {
  /**
   * 创建一个新的 CustomEventSource 实例
   * @param {string} url - 服务器事件源的 URL
   * @param {Object} [options={}] - 配置选项
   * @param {Object} [options.headers={}] - 请求头
   * @param {boolean} [options.autoReconnect=true] - 是否自动重连
   * @param {number} [options.reconnectDelay=3000] - 重连延迟时间（毫秒）
   * @param {number} [options.maxReconnectAttempts=5] - 最大重连尝试次数
   * @param {boolean} [options.autoManageVisibility=true] - 是否自动管理页面可见性
   * @param {EventParser} [eventParser] - 自定义事件解析器
   */
  constructor(url, options = {}, eventParser) {
    this.url = url;
    this.headers = options.headers || {};
    this.onmessage = null;
    this.onerror = null;
    this.onopen = null;

    // 重连配置
    this.autoReconnect = options.autoReconnect ?? true;
    this.reconnectDelay = options.reconnectDelay || 3000;
    this.maxReconnectAttempts = options.maxReconnectAttempts || 5;

    // 页面可见性管理
    this.autoManageVisibility = options.autoManageVisibility ?? true; // 默认开启可见性管理
    this.isConnected = false;
    this.wasConnected = false; // 记录页面隐藏前的连接状态

    this.reconnectAttempts = 0;
    this.abortController = null;

    if (this.autoManageVisibility) {
      this.handleVisibilityChange = this.handleVisibilityChange.bind(this);
      document.addEventListener(
        "visibilitychange",
        this.handleVisibilityChange
      );
    }

    if (document.visibilityState === "visible") {
      this.connect();
    }

    this.eventParser = eventParser || new DefaultEventParser();
  }

  /**
   * 处理页面可见性变化
   * @private
   */
  handleVisibilityChange() {
    if (document.visibilityState === "visible") {
      // 页面变为可见时，如果之前是连接状态，则重新连接
      if (this.wasConnected) {
        this.connect();
      }
    } else {
      // 页面隐藏时，记录当前状态并断开连接
      this.wasConnected = this.isConnected;
      if (this.isConnected) {
        this.close();
      }
    }
  }

  /**
   * 连接到事件源
   * @returns {Promise<void>}
   */
  async connect() {
    if (this.isConnected) {
      return;
    }

    try {
      this.abortController = new AbortController();

      const response = await fetch(this.url, {
        headers: this.headers,
        signal: this.abortController.signal,
      });

      this.isConnected = true;
      if (this.onopen) {
        this.onopen();
      }

      this.reconnectAttempts = 0;

      const reader = response.body.getReader();
      const decoder = new TextDecoder();
      let buffer = "";

      while (true) {
        const { value, done } = await reader.read();
        if (done) break;

        buffer += decoder.decode(value, { stream: true });
        const messages = buffer.split("\n\n");
        buffer = messages.pop() || "";

        messages.forEach((message) => {
          const data = this.parseEvent(message);
          if (data && this.onmessage) {
            this.onmessage({ data });
          }
        });
      }
    } catch (error) {
      if (error.name === "AbortError") {
        console.log("连接被主动中断");
        return;
      }

      this.handleError(error);
    } finally {
      this.isConnected = false;
    }
  }

  /**
   * 解析事件数据
   * @private
   * @param {string} eventString - 要解析的事件字符串
   * @returns {string|null} 解析后的数据
   */
  parseEvent(eventString) {
    return this.eventParser.parse(eventString);
  }

  /**
   * 尝试重新连接
   * @private
   * @returns {Promise<void>}
   */
  async reconnect() {
    if (!this.autoReconnect) {
      console.log("自动重连已禁用");
      return;
    }

    if (this.reconnectAttempts >= this.maxReconnectAttempts) {
      console.log("达到最大重连次数，停止重连");
      this.close();
      return;
    }

    this.reconnectAttempts++;
    console.log(
      `尝试重连 (${this.reconnectAttempts}/${this.maxReconnectAttempts})`
    );

    this.close();

    await new Promise((resolve) => setTimeout(resolve, this.reconnectDelay));
    this.connect();
  }

  /**
   * 处理错误
   * @private
   * @param {Error} error - 错误对象
   */
  handleError(error) {
    if (this.onerror) {
      this.onerror(error);
    }
    this.reconnect();
  }

  /**
   * 关闭连接
   */
  close() {
    this.isConnected = false;
    if (this.abortController) {
      this.abortController.abort();
      this.abortController = null;
    }
  }

  /**
   * 销毁实例，清理资源
   */
  destroy() {
    this.close();
    if (this.autoManageVisibility) {
      document.removeEventListener(
        "visibilitychange",
        this.handleVisibilityChange
      );
    }
  }
}

export default CustomEventSource;

Typescript

// 自定义事件源配置选项接口
interface CustomEventSourceOptions {
  headers?: Record<string, string>; // 添加 headers 选项
  autoReconnect?: boolean; // 是否自动重连
  reconnectDelay?: number; // 重连延迟时间（毫秒）
  maxReconnectAttempts?: number; // 最大重连尝试次数
  autoManageVisibility?: boolean; // 是否自动管理页面可见性
}

// 自定义事件对象接口
interface CustomEventSourceEvent {
  data: string; // 事件数据
}

// 事件处理器类型定义
type EventHandler = (event: CustomEventSourceEvent) => void; // 消息处理器
type ErrorHandler = (error: Error) => void; // 错误处理器
type OpenHandler = () => void; // 连接打开处理器

// 事件解析器接口
interface EventParser {
  parse(eventString: string): string | null; // 解析事件字符串
}

// 默认事件解析器实现
class DefaultEventParser implements EventParser {
  parse(eventString: string): string | null {
    // 将输入按行分割，去除空白字符，过滤空行，并重新组合
    const lines = eventString
      .split("\n")
      .map((line) => line.trim())
      .filter(Boolean);
    return lines.length > 0 ? lines.join("\n") : null;
  }
}

class CustomEventSource {
  private url: string;
  private headers: Record<string, string>;
  private autoReconnect: boolean;
  private reconnectDelay: number;
  private maxReconnectAttempts: number;
  private autoManageVisibility: boolean;
  private isConnected: boolean;
  private wasConnected: boolean;
  private reconnectAttempts: number;
  private abortController: AbortController | null;
  private eventParser: EventParser;

  public onmessage: EventHandler | null;
  public onerror: ErrorHandler | null;
  public onopen: OpenHandler | null;

  constructor(
    url: string,
    options: CustomEventSourceOptions = {},
    eventParser?: EventParser
  ) {
    this.url = url;
    this.headers = options.headers || {};
    this.onmessage = null;
    this.onerror = null;
    this.onopen = null;

    // 重连配置
    this.autoReconnect = options.autoReconnect ?? true;
    this.reconnectDelay = options.reconnectDelay || 3000;
    this.maxReconnectAttempts = options.maxReconnectAttempts || 5;

    // 页面可见性管理
    this.autoManageVisibility = options.autoManageVisibility ?? true;
    this.isConnected = false;
    this.wasConnected = false;

    this.reconnectAttempts = 0;
    this.abortController = null;

    if (this.autoManageVisibility) {
      this.handleVisibilityChange = this.handleVisibilityChange.bind(this);
      document.addEventListener(
        "visibilitychange",
        this.handleVisibilityChange
      );
    }

    if (document.visibilityState === "visible") {
      this.connect();
    }

    this.eventParser = eventParser || new DefaultEventParser();
  }

  private handleVisibilityChange(): void {
    if (document.visibilityState === "visible") {
      if (this.wasConnected) {
        this.connect();
      }
    } else {
      this.wasConnected = this.isConnected;
      if (this.isConnected) {
        this.close();
      }
    }
  }

  public async connect(): Promise<void> {
    if (this.isConnected) {
      return;
    }

    try {
      this.abortController = new AbortController();

      const response = await fetch(this.url, {
        headers: this.headers,
        signal: this.abortController.signal,
      });

      this.isConnected = true;
      if (this.onopen) {
        this.onopen();
      }

      this.reconnectAttempts = 0;

      const reader = response.body!.getReader();
      const decoder = new TextDecoder();
      let buffer = "";

      while (true) {
        const { value, done } = await reader.read();
        if (done) break;

        buffer += decoder.decode(value, { stream: true });
        const messages = buffer.split("\n\n");
        buffer = messages.pop() || "";

        messages.forEach((message) => {
          const data = this.parseEvent(message);
          if (data && this.onmessage) {
            this.onmessage({ data });
          }
        });
      }
    } catch (error) {
      if (error instanceof Error && error.name === "AbortError") {
        console.log("连接被主动中断");
        return;
      }

      this.handleError(error as Error);
    } finally {
      this.isConnected = false;
    }
  }

  private parseEvent(eventString: string): string | null {
    return this.eventParser.parse(eventString);
  }

  private async reconnect(): Promise<void> {
    if (!this.autoReconnect) {
      console.log("自动重连已禁用");
      return;
    }

    if (this.reconnectAttempts >= this.maxReconnectAttempts) {
      console.log("达到最大重连次数，停止重连");
      this.close();
      return;
    }

    this.reconnectAttempts++;
    console.log(
      `尝试重连 (${this.reconnectAttempts}/${this.maxReconnectAttempts})`
    );

    this.close();

    await new Promise((resolve) => setTimeout(resolve, this.reconnectDelay));
    this.connect();
  }

  private handleError(error: Error): void {
    if (this.onerror) {
      this.onerror(error);
    }
    this.reconnect();
  }

  public close(): void {
    this.isConnected = false;
    if (this.abortController) {
      this.abortController.abort();
      this.abortController = null;
    }
  }

  public destroy(): void {
    this.close();
    if (this.autoManageVisibility) {
      document.removeEventListener(
        "visibilitychange",
        this.handleVisibilityChange
      );
    }
  }
}

export default CustomEventSource;

食用文档

import ModernEventSource from "./ModernEventSource.js";

const eventSource = new ModernEventSource("http://localhost:3000/events", {
  autoReconnect: true, // 启用自动重连
  reconnectDelay: 2000, // 2秒后重连
  maxReconnectAttempts: 3, // 最多重连3次
  autoManageVisibility: true, // 启用页面可见性管理
  headers: {
    "X-App": "MyApp",
    "X-Token": "my-custom-token",
  },
});

eventSource.onopen = function () {
  console.log("连接已建立");
};

eventSource.onmessage = function (event) {
  console.log("接收到的消息：", event);
};

eventSource.onerror = function (error) {
  console.error("SSE 错误：", error);
};

// 在页面卸载时清理资源
window.addEventListener("unload", () => {
  eventSource.destroy();
});