Example of NodeJS Loop of Mongo to Elasticsearch

mongoToES.js

// npm install elasticsearch
// setup nodejs client for elasticsearch
// documentation: https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/index.html
var elasticsearch = require('elasticsearch');
var EsClient = new elasticsearch.Client({
  host: 'localhost:9200',
  log: 'info'
});


// npm install mongodb
// setup nodjs driver for MongoDB
var MongoClient = require('mongodb').MongoClient;
var ObjectID = require('mongodb').ObjectID;
var mongoDBName = 'heroes';
var mongoCollectionName = 'characters';
var connectionString = 'mongodb://127.0.0.1:27017/'; // put username and password for mongo here

var esIndexName = 'herocharacters';



// connect to Mongodb
MongoClient.connect(connectionString+mongoDBName, function(err, db) {
    if(err) throw err;
   
   // for each object in a collection
   var collection = db.collection(mongoCollectionName);
   var counter = 0;
   collection.find().each(function(err, item) {
     if(item != null) {
       
       
       if(counter % 100 == 0) console.log( "Syncing object id: "+ item['_id'] + " #: " + counter);

       EsClient.index(
         {index: esIndexName, type:mongoCollectionName,  id: item._id.toString() , body:  item  },
         function(error, response) {
           if(err) throw err;
         }
       );
       
     }
     counter += 1;
   });
    
});

Nice job!

Field [_id] is a metadata field and cannot be added inside a document. Use the index API request parameters. Having this issue. Tried renaming id field to other name but no luck. It processed some of the documents.