如何与 MongoDb 同步数据并了解文档是否成功创建/更新

Question

I'm developing a MERN chat app and trying to replicate the feature which WhatsApp provides -> message sent/seen status, so for that I need to check whether the message I/user sent is successfully synced/updated/created in my MongoDB , I know similar functionality can be achieved in AWS Amplify using the event outboxMutationEnqueued which says Dispatched when a local change has been newly staged for synchronization with the cloud , so it works like whenever we are trying to push something to synchronize with the cloud, this event is going to be fired, and once it is finished, outboxMutationProcessed is going to be triggered which says Dispatched when a local change has finished syncrhonization with the cloud and is updated locally .

So we can listen to these events whenever we are trying to send a message, and once our message mutation is processed we are going to receive outboxMutationProcessed , and then we can update the status of the message to sent or single tick or delivered .

import Amplify, {Hub} from 'aws-amplify';

useEffect(() => {
  const listener = Hub.listen('datastore', async (hubData) => {
    const {event, data} = hubData.payload;
    if (event === 'networkStatus') {
      console.log('User has a network connection: ', data.active);
    }
    if (event === 'outboxMutationProcessed') {
      if (data.model === Message)
        console.log('Mutation has been synced with the cloud: ', data);
        // set the message status to delivered.
    }
  })
  return () => listener();
}, []);

So, the question, do we have something similar in MongoDB ? I'm currently using React Native, Node, Express, Sockets, Mongoose, MongoDB.

Currently, my API end point (for creating a new message and saving in to db):

router.post('/create_message', checkAuth, async (req, res) => {
  const {chatRoomId, senderId, text} = req.body;
  try {
    const message = new Message({
      chatRoomId,
      senderId,
      text,
    });
    const result = await message.save();

    return res.status(200).json({
      type: 'success',
      data: result,
    });
  } catch (error) {
    return res.status(422).send({error: `${error.message}`});
  }
});

// SOCKET IMPLEMENTATION FOR REALTIME FEATURE

socket.on('listener', async data => {
  io.to(id).emit('new_message', data);
  const message = new Message({
    chatRoomId: data.roomId,
    senderId: data.senderId,
    text: data.text,
  });
  await message.save();
  // maybe something here...? not sure
});

Maybe an event which we can fire, during the await message.save(...something here...) , and if it is successfully saved in our DB, we can send it to our frontend or using socket?

If anyone could provide an example, it would be really helpful!

Answer 1

Could you do something like:

schema:

{
from: ObjectId,
to: ObjectId,
 message: String,
delivered: Date,
readBy: []}

app.js

conn = new Mongo("YOUR_CONNECTION_STRING");
db = conn.getDB('chat');

const pipeline = [
  { $match: { 'fullDocument.from': 'johnID...' } },
  { $set: { delivered: new Date() } }
];

const collection = db.collection('messages');
const changeStream = collection.watch(pipeline);
changeStream.on('change', function(change){
if(change.fullDocument.delivered){
  //Notify user of delivery
}
if(change.fullDocument.readBy.includes("otherUserID"){
//notify user of read
}
});