解决Firebase Admin SDK数据读取超时：掌握异步操作的正确姿势

import * as admin from 'firebase-admin';
const serviceAccount = require('/config/firebase/..json');

const fcmInitialize = {
  credential: admin.credential.cert(serviceAccount), // 假设agent已定义
  databaseURL: 'YOUR_FIREBASE_DATABASE_URL' // 使用实际的URL
};

const fcm = admin.initializeApp(fcmInitialize);
admin.database().enableLogging(true); // 注意：这里应直接调用admin.database()

// 错误示例：不当使用await
async function getChatrooms(userId: string) {
  await fcm.auth(); // 此处fcm.auth()通常不返回Promise，await无效
  const database = await fcm.database(); // fcm.database()同步返回数据库实例，await无效

  console.log('initiate chatrooms');
  const chatroomPath = await database.ref(`chatrooms/${userId}`); // database.ref()同步返回引用，await无效

  let chatrooms;
  // 问题所在：对once()的callback函数使用await和async
  await chatroomPath.orderByChild('timestamp').once('value', async snapshot => {
    console.log('enter chatrooms');
    if (snapshot.val()) {
      chatrooms = await snapshot.val(); // snapshot.val()同步返回数据，await无效
      console.log(chatrooms);
    }
  });
  console.log(`chatrooms: ${chatrooms}`); // 此行会在数据加载前执行
}

import * as admin from 'firebase-admin';

// ... (Firebase 初始化代码与之前相同)
const fcm = admin.initializeApp(fcmInitialize);
admin.database().enableLogging(true);

function getChatroomsWithCallback(userId: string) {
  // fcm.auth()通常不需要await，因为它主要用于初始化认证服务，而不是等待一个特定的认证结果。
  fcm.auth();
  const database = fcm.database();

  console.log('initiate chatrooms');
  const chatroomPath = database.ref(`chatrooms/${userId}`);

  chatroomPath.orderByChild('timestamp').once('value', snapshot => {
    // 数据加载成功后，此回调函数才会被执行
    console.log('enter chatrooms');
    let chatrooms;
    if (snapshot.val()) {
      chatrooms = snapshot.val(); // snapshot.val()同步返回数据
      console.log(chatrooms);
    }
    // 依赖于chatrooms数据的逻辑必须放在这里
    console.log(`chatrooms: ${chatrooms}`);
    // 可以在这里处理响应，例如将chatrooms返回给API调用者
  });
  // 注意：此处代码会在数据加载前执行，不能依赖chatrooms
  console.log('Exiting getChatroomsWithCallback function, data might not be ready yet.');
}

// 示例调用
// getChatroomsWithCallback('someUserId');

import * as admin from 'firebase-admin';

// ... (Firebase 初始化代码与之前相同)
const fcm = admin.initializeApp(fcmInitialize);
admin.database().enableLogging(true);

async function getChatroomsWithAwait(userId: string) {
  // fcm.auth()通常不需要await
  fcm.auth();
  const database = fcm.database();

  console.log('initiate chatrooms');
  const chatroomPath = database.ref(`chatrooms/${userId}`);

  let chatrooms;
  try {
    // 关键点：await ref().once('value')，等待Promise解析
    const snapshot = await chatroomPath.orderByChild('timestamp').once('value');
    console.log('enter chatrooms'); // 此行将在数据获取后执行

    if (snapshot.val()) {
      chatrooms = snapshot.val(); // snapshot.val()同步返回数据
    }
    console.log(`chatrooms: ${chatrooms}`);
    return chatrooms; // 如果在一个async函数中，可以返回数据
  } catch (error) {
    console.error('Error fetching chatrooms:', error);
    // 处理错误，例如抛出异常或返回空数据
    throw error;
  }
}

// 示例调用 (在一个async函数中调用)
// async function main() {
//   try {
//     const userChatrooms = await getChatroomsWithAwait('someUserId');
//     console.log('User chatrooms:', userChatrooms);
//   } catch (e) {
//     console.error('Failed to get chatrooms:', e);
//   }
// }
// main();