MongoDB 更改流和池大小：如何在请求之间共享连接

Question

After implementing change streams the performance of mongodb dropped dramatically. Now I've disabled the websockets on my client, because the database cannot handle such load. The root of the problem is the number of connections to the database that has been made. Maybe it is possible to share the same change stream to mongodb across clients.

App.ts

const socketServer = require('https').createServer(sslOptions, app).listen(4001, () => {
  console.log('Socket.io Server running on port 4001')
})
const io = require('socket.io')(socketServer)

io.on('connection', (socket: Socket) => {
  const {profileId} = socket?.handshake?.query

  if (profileId) {
    watchProfile(profileId, (profile: ProfileDocument) => {
      socket.emit('updateProfile', profile)
    })
  }
}

Watch Profile

// Gets updates for a profile
export const watchProfile = (profileId: string, onChange: Function) => {
  Profile.watch(
    [{
      $match: {
        'fullDocument._id': ObjectId(profileId)
      }
    }], {
      fullDocument: 'updateLookup'
    }
  ).on('change', (data: any) => {
    const profile: ProfileDocument = data.fullDocument
    onChange(profile)
  })
}

So everytime a connection is opened by the client, watchProfile instantiates a change stream specifically for this profile or user. However, this just doesn't work for 100s of users. Therefore, I would like to ask if there are some patterns that will work. Maybe it is possible to not instantiate a new connection for every client, but just have one cursor ready and filter it for every user in a later stage.

Already attempted to increase the poolSize to a larger number (100), which worked very well locally but not on the free tier of MongoDB Atlas.

Answer 1

Change streams do not require dedicated connections - they will use connections in the pool for the duration of each getMore operation.