在mongodb的两个集合中保存消息时使用`mongoose transactions`

Question

如果学生向老师发送消息，则消息将保存在 teachers 和 students 集合中。同样的情况是当老师给学生发送消息时，他们也保存在teachers和students这两个集合中。如何在以下代码中应用mongoose transaction 以便将消息保存在两个集合中。我不希望消息将保存在一个集合中而另一个集合中由于错误而不会保存的情况。我正在寻求帮助和线索

const express = require('express');
const mongoose = require('mongoose');
require('dotenv').config();

//const app = express();

// Connect to our Database and handle an bad connections
module.exports.db = mongoose
    .createConnection(process.env.DATABASE, { 
        useNewUrlParser: true, 
        useFindAndModify: false,
        useUnifiedTopology: true, 
        useCreateIndex: true
    }
);




//controller
const db = require('./connection');

const session = db.startSession();
session.startTransaction();

module.exports.sendMessage = (req, res) => {
    
    let {sender, receiver, msg, role} = req.body;
    var hex = /[0-9A-Fa-f]{6}/g;

    sender = (hex.test(sender))? mongoose.Types.ObjectId(sender) : sender;
    receiver = (hex.test(receiver))? mongoose.Types.ObjectId(receiver) : receiver;
    console.log(sender, receiver, msg, 'send');

            if(role === 'tutor') {
                let teacherMessage =  new TeacherMessageSchema.TeacherMessageSchema({
                    contentInfo : {
                        msg : msg
                    },
                    sender : sender
                })

                let studentMessage =  new TeacherMessageSchema.TeacherMessageSchema({
                    contentInfo : {
                        msg : msg
                    },
                    receiver : receiver
                })
        
                db.db.collection('teachers').findOneAndUpdate( 
                    { _id : receiver },
                    { $push: { messages: teacherMessage } },
                    (err, updated) => {
                        console.log(updated, 'vvv');
        
                        updated.value.hashed_password = undefined;
                        updated.value.salt = undefined;
        
                        if(err) {
                            res.status(404).json(err);
                        }
        
                        if (updated) {
                            res.status(200).json(updated.value);

                            db.db.collection('students').findOneAndUpdate( 
                                { _id : sender },
                                { $push: { messages: studentMessage } },
                               
                            );
                        }
                    }, session(session)
                )
        
              
            }
        
        
            if(role === 'student') {
                let studentMessage =  new StudentMessageSchema.StudentMessageSchema({
                    contentInfo : {
                        msg : msg
                    },
                    receiver : receiver
                })

                let teacherMessage =  new TeacherMessageSchema.TeacherMessageSchema({
                    contentInfo : {
                        msg : msg
                    },
                    sender : sender
                })
        
               
        
                db.db.collection('students').findOneAndUpdate( 
                    { _id : sender },
                    { $push: { messages: studentMessage } },
                    (err, updated) => {
                        console.log(updated, 'sss');
            
                        updated.value.hashed_password = undefined;
                        updated.value.salt = undefined;
            
                        if(err) {
                            res.status(404).json(err);
                        }
            
                        if (updated) {
                            res.json(updated.value);
                            db.db.collection('teachers').findOneAndUpdate( 
                                { _id : receiver },
                                { $push: { messages: teacherMessage } },
                               
                            )
                        }
                    }, 
                ), session(session)
            }
}

记录的变量 db

{
  db: NativeConnection {
    base: Mongoose {
      connections: [Array],
      models: [Object],
      modelSchemas: [Object],
      options: [Object],
      _pluralize: [Function: pluralize],
      plugins: [Array]
    },
    collections: {},
    models: {},
    config: { autoIndex: true },
    replica: false,
    options: null,
    otherDbs: [],
    relatedDbs: {},
    states: [Object: null prototype] {
      '0': 'disconnected',
      '1': 'connected',
      '2': 'connecting',
      '3': 'disconnecting',
      '99': 'uninitialized',
      disconnected: 0,
      connected: 1,
      connecting: 2,
      disconnecting: 3,
      uninitialized: 99
    },
    _readyState: 1,
    _closeCalled: false,
    _hasOpened: true,
    _listening: false,
    _connectionOptions: {
      useNewUrlParser: true,
      useFindAndModify: false,
      useUnifiedTopology: true,
      useCreateIndex: true,
      promiseLibrary: [Function: Promise]
    },
    client: MongoClient {
      _events: [Object: null prototype] {},
      _eventsCount: 0,
      _maxListeners: undefined,
      s: [Object],
      topology: [ReplSet],
      [Symbol(kCapture)]: false
    },
    name: null,
    '$initialConnection': Promise { [Circular] },
    db: Db {
      _events: [Object: null prototype],
      _eventsCount: 3,
      _maxListeners: undefined,
      s: [Object],
      serverConfig: [Getter],
      bufferMaxEntries: [Getter],
      databaseName: [Getter],
      [Symbol(kCapture)]: false
    }
  }
}

Answer 1

我已经在代码中添加了Anytime有错误：

等待 session.abortTransaction();

否则（快乐路径）提交更改。

等待 session.commitTransaction();

Abort 和 commit 是 Promise 的基本函数，所以我更改了它们用作异步的函数。

const express = require('express');
const mongoose = require('mongoose');
require('dotenv').config();

//const app = express();

// Connect to our Database and handle an bad connections
module.exports.db = mongoose
    .createConnection(process.env.DATABASE, { 
        useNewUrlParser: true, 
        useFindAndModify: false,
        useUnifiedTopology: true, 
        useCreateIndex: true
    }
);




//controller
const db = require('./connection');



module.exports.sendMessage = async (req, res) => {
    
    const session = await db.startSession();
    session.startTransaction();

    let {sender, receiver, msg, role} = req.body;
    var hex = /[0-9A-Fa-f]{6}/g;

    sender = (hex.test(sender))? mongoose.Types.ObjectId(sender) : sender;
    receiver = (hex.test(receiver))? mongoose.Types.ObjectId(receiver) : receiver;
    console.log(sender, receiver, msg, 'send');

            if(role === 'tutor') {
                let teacherMessage =  new TeacherMessageSchema.TeacherMessageSchema({
                    contentInfo : {
                        msg : msg
                    },
                    sender : sender
                })

                let studentMessage =  new TeacherMessageSchema.TeacherMessageSchema({
                    contentInfo : {
                        msg : msg
                    },
                    receiver : receiver
                })
        
                db.db.collection('teachers').findOneAndUpdate( 
                    { _id : receiver },
                    { $push: { messages: teacherMessage } },
                    async (err, updated) => {
                        console.log(updated, 'vvv');
        
                        updated.value.hashed_password = undefined;
                        updated.value.salt = undefined;
        
                        if(err) {
                            await session.abortTransaction();
                            res.status(404).json(err);
                            return
                        }
        
                        if (updated) {
                            res.status(200).json(updated.value);

                            db.db.collection('students').findOneAndUpdate( 
                                { _id : sender },
                                { $push: { messages: studentMessage } },
                               
                            );
                        }
                    }, session(session)
                )
        
              
            }
        
        
            if(role === 'student') {
                let studentMessage =  new StudentMessageSchema.StudentMessageSchema({
                    contentInfo : {
                        msg : msg
                    },
                    receiver : receiver
                })

                let teacherMessage =  new TeacherMessageSchema.TeacherMessageSchema({
                    contentInfo : {
                        msg : msg
                    },
                    sender : sender
                })
        
               
        
                db.db.collection('students').findOneAndUpdate( 
                    { _id : sender },
                    { $push: { messages: studentMessage } },
                    async (err, updated) => {
                        console.log(updated, 'sss');
            
                        updated.value.hashed_password = undefined;
                        updated.value.salt = undefined;
            
                        if(err) {
                            await session.abortTransaction();
                            res.status(404).json(err);
                            return;
                        }
            
                        if (updated) {
                            res.json(updated.value);
                            db.db.collection('teachers').findOneAndUpdate( 
                                { _id : receiver },
                                { $push: { messages: teacherMessage } },
                               
                            )
                        }
                    }, 
                    session(session)
                )
            }

            await session.commitTransaction();
}