javascript - 来自 Cloud Function 的未处理拒绝，但它有时会运行

Question

我有一些代码有时有效，但有时却无效。当它不运行时，我得到这个错误:

这是我在 Javascript 中的代码:

exports.handleRequest = functions.database.ref('/Request/{usersUID}/{autoID}/{request}').onWrite(event => {
  let request = event.data.val();
  let additionalRequest = event.data.key;
  let usersUID = event.params.usersUID;
  const generatedAutoID = event.params.autoID;
  event.data.adminRef.remove();
  if (event.data.previous.exists()) {
        return;
  }
  if (!event.data.exists()) {
        return;
  }
  const functions = require('firebase-functions');
  const admin = require('firebase-admin');
  admin.initializeApp(functions.config().firebase);
  var db = admin.database();

  var MasterAllCards = ["2_of_clubs", "2_of_spades", "2_of_diamonds", "2_of_hearts", "3_of_clubs", "3_of_spades", "3_of_diamonds", "3_of_hearts", "4_of_clubs", "4_of_spades", "4_of_diamonds", "4_of_hearts", "5_of_clubs", "5_of_spades", "5_of_diamonds", "5_of_hearts", "6_of_clubs", "6_of_spades", "6_of_diamonds", "6_of_hearts", "7_of_clubs", "7_of_spades", "7_of_diamonds", "7_of_hearts", "8_of_clubs", "8_of_spades", "8_of_diamonds", "8_of_hearts", "9_of_clubs", "9_of_spades", "9_of_diamonds", "9_of_hearts", "10_of_clubs", "10_of_spades", "10_of_diamonds", "10_of_hearts", "jack_of_clubs", "jack_of_spades", "jack_of_diamonds", "jack_of_hearts", "queen_of_clubs", "queen_of_spades", "queen_of_diamonds", "queen_of_hearts", "king_of_clubs", "king_of_spades", "king_of_diamonds", "king_of_hearts", "ace_of_clubs", "ace_of_spades", "ace_of_diamonds", "ace_of_hearts"]
  var MasterAllValues = [2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14]
  function getRandomInt(min, max) {
        return Math.floor(Math.random() * (max - min + 1)) + min;
  }
  let pathToUsersTickets = db.ref('/users/' + usersUID + '/serverSideValues/Tickets');
  var usersTickets = 0;
  pathToUsersTickets.transaction(function(current) {
        return (current || 0) - 1;
  }).then(function(ticket) {
        usersTickets = Number(ticket.snapshot.val())
  });
  if (usersTickets >= 0) {
        let pathSettingUpGame = db.ref('/Checkrequests/' + usersUID + '/' + request); 
        let pathServer = db.ref('/Checkrequests/' + usersUID + '/' + request + '/Server');
        var tags = [];
        var images = [];
        var allCards = MasterAllCards
        var allCardsTags = MasterAllValues
        var i = 0;
        while (i < 5) {
              let randomc = getRandomInt(0, 51 - i);
              images.push(allCards[randomc])
              tags.push(allCardsTags[randomc])
              allCards.splice(randomc, 1);
              allCardsTags.splice(randomc, 1);
              i++
        }
        console.log(images);
        console.log(tags[0])
        console.log(allCards);
        console.log(allCardsTags) 
        pathSettingUpGame.update({
              "mastercard": images[0],
              "highlowgametier" : 1
        })    
        pathServer.update({
              "child1image" : images[1],
              "child2image" : images[2],
              "child3image" : images[3],
              "child4image" : images[4],
              "child1tag" : tags[1],
              "child2tag" : tags[2],
              "child3tag" : tags[3],
              "child4tag" : tags[4],
        })
   }
})

但有时它确实可以毫无错误地运行。您可以查看 here 上的代码，其中 images[0] 始终是一个字符串并且永远不会为空。怎么有时会出现这个问题呢？ 没有错误:

有时我会这样，注意第三个值中的未定义:

Answer 1

间歇性故障可能是由于您没有为您的代码执行的大量异步 Firebase 操作返回 Promise 而造成的。 Cloud Functions Guide解释:

It's important to manage the lifecycle of a function to ensure that it resolves properly... Also, you can make sure that the Cloud Functions instance running your function does not shut down before your function successfully reaches its terminating condition or state.

• Resolve functions that perform asynchronous processing by returning a JavaScript promise

您的代码包含对 remove()、transaction() 和 update() 的调用。其中每一个都异步完成并返回一个 Promise。您需要根据需要链接或组合(参见 Promise.all())返回的 Promise，以确保您的函数为任何正在进行的异步 Firebase 操作返回 Promise。

例如，要在发布的代码末尾处理对 update() 的两次调用:

const prom1 = pathSettingUpGame.update({
    ...
});

const prom2 = pathServer.update({
    ...
});

return Promise.all([prom1, prom2]);

还有一个Firebase video on returning Promises .