Implementation of MongoDB Changestream

Question

I am facing some issues while implementing changestream of mongodb in nestJS. Here is the code

export class UsersService {
  constructor(
    @InjectModel('User')
    private userModel: Model<User>,
  ) {}
  private changeStream: ChangeStream;
  private readonly pipeline = [
    {
      $match: {
        operationType: 'insert',
      },
    },
  ];
  async onModuleInit() {
    console.log('inside module init');
    await this.startChangeStream();
  }
  async startChangeStream() {
    this.changeStream = this.userModel.watch(this.pipeline, {
      fullDocument: 'updateLookup',
    });

    this.changeStream.on('change', async ({ fullDocument }: any) => {
      console.log('Change:', fullDocument);

    })
  
  async updateUser(updateUserDTO: UpdateUserDTO) { 
      //logic
  }
}

I am using updateUser method of UsersService to update name of the user. The name gets updated but the changestream does not get triggered.

What am I doing wrong here?

I tried shifting code from here and there, event tried providing this as module through app module but it didn't work. I'm expecting this changestream to work.

Answer 1

I think you need to update the pipeline as well

private readonly pipeline = [
  {
    $match: {
      $or: [
        { operationType: 'insert' },
        { operationType: 'update' }, // Match update operations
      ],
    },
  },
];