MongooseError [ParallelSaveError]: Can't save() the same doc multiple times in parallel

Question

I am having an issue with mongoose and nodejs. May be i am writing wrong code or any other problem please help. Here is my controller file. alldata.save gives [ParallelSaveError]

let createData = async function(req,res,next) {
    let body = req.body;
    let alldata = new League(body);
    let start_time = new Date().getTime();
    try {
         await Leaguecategories.find({})
                .then(async function(categories) {  
                    categories.forEach(async function(category) {
                      //here i am assigning foreign key
                        alldata.league_category_id = category._id;
                       await alldata.save(function(err, book){
                            if(err){
                                console.log(err);
                            }else{
                            res.send({status: 0, statusCode:"success", message: "Successfully inserted."})
                            }
                       });
                    })     
                })
    }
    catch (error){
        return res.send({status : 1 , statusCode : "error" , message : error.message})
    }
}

Here is my Leaguecategories model

var mongoose = require('mongoose');


const league_categories = new mongoose.Schema({
    name: {
      type: String,
      required: true
    },
    active: {
      type: String,
      required: true
    },
    create_date: {
      type: Date,
      required: true,
      default: Date.now
    },
    league_type_id: {
      type: String,
      required: 'league_type',
      required:true
    }
  })

  module.exports = mongoose.model('Leaguecategories', league_categories)

Here is my League model

var mongoose = require('mongoose');

    const league = new mongoose.Schema({
        title: {
            type: String,
            required: true
          },
          pool_price: {
              type: Number,
              required: true
          },
          entry_fee: {
              type: Number,
              required: true
          },
          total_spots: {
              type: Number,
              required: true
          },
          start_time: {
            type: Date,
            required: true
          },
          end_time: {
            type: Date,
            required: true
          },
          create_date: {
            type: Date,
            required: true,
            default: Date.now
          },
          active: {
            type: String,
            required: true
          },
          league_category_id: {
            type: String,
            ref: 'Leaguecategories',
            required:true
          }
    })

    module.exports = mongoose.model('League', league)

Answer 1

You have to create new instance of League each time. Like this:

categories.forEach(async function(category) {
  //here i am assigning foreign key
  let alldata = new League(body);
  alldata.league_category_id = category._id;
  ...
});

Suggestion:

Why are you using both async/await and .then()? You should use only one of them. Also, there are some other problems.

• await won't work inside forEach
• You are calling res.send() every time you call .save(). This might end up throwing an error as well.

You can refactor the code like this.

try {
  const categories = await Leaguecategories.find({});
  const promises = categories.map(function (category) {
    //here i am assigning foreign key
    let alldata = new League(body);
    alldata.league_category_id = category._id;
    return alldata.save();
  });

  await Promise.all(promises);

  res.send({ status: 0, statusCode: "success", message: "Successfully inserted." })
} catch (error) {
  return res.send({ status: 1, statusCode: "error", message: error.message });
}