nodejs mongo workers

findCallback.js

    var dbUrl = 'mongodb://username:[email protected]:port/database-name';
    MongoClient.connect(
      dbUrl,
      function(err, db) {
        if(err) throw err;
        db.collection('ItemModel').find({}).toArray(function(err, docs) {
          console.dir(docs);
          console.dir(docs.length);
          db.close();
        });
      });

findOneCallback.js

    var dbUrl = 'mongodb://username:[email protected]:port/database-name';
    MongoClient.connect(
      dbUrl,
      function(err, db) {
        if(err) throw err;
        db.collection('ItemModel').findOne({}, function(err, doc) {
          console.dir(doc);
          db.close();
        });
      });

findPromiseComplex.js

    // Inject bluebird as mongo preferred promise library:
    // https://easyusedev.wordpress.com/2015/10/07/mongodb-using-bluebird-promises-with-mongo-db-native-driver-2-0-mongodb-node-driver/
    var Promise = require('bluebird');
    var dbUrl = 'mongodb://username:[email protected]:port/database-name';
    var collectionName = 'MyCollection';
    MongoClient
      .connect(params.dbUrl, {
        promiseLibrary: Promise
      })
      // TODO: https://www.snip2code.com/Snippet/974049/Algorithm-to-loop-through-a-large-MongoD
      .then(function(db) {
        return db
          .collection(collectionName)
          .find({}) // find returns cursor
          .toArray() // cursor methods return promises: http://mongodb.github.io/node-mongodb-native/2.1/api/Cursor.html#toArray
          .then(function(documents) {
            logger.log('documents.length', documents.length);
            return Promise.map(
              documents || [],
              function(document){
                logger.log(document.name);
                return db
                  .collection(collectionName)
                  .findOne({_id: document._id})
                  .then(function(doc) {
                    logger.log('doc:', doc);
                    return Promise.resolve();
                  });
              },
              {concurrency: 1}
            );
          })
          .finally(db.close.bind(db));
      })
      .catch(function(err) {
        console.error("ERROR", err);
      });

findPromiseSimple.js

    // Inject bluebird as mongo preferred promise library:
    // https://easyusedev.wordpress.com/2015/10/07/mongodb-using-bluebird-promises-with-mongo-db-native-driver-2-0-mongodb-node-driver/
    var Promise = require('bluebird');
    var dbUrl = 'mongodb://username:[email protected]:port/database-name';
    MongoClient
      .connect(dbUrl, {
        promiseLibrary: Promise
      })
      .then(function(db) {
        return db
          .collection('ItemModel')
          .find({}) // find returns cursor
          .toArray() // cursor methods return promises: http://mongodb.github.io/node-mongodb-native/2.1/api/Cursor.html#toArray
          .then(function(documents) {
            logger.log('documents.length', documents.length);
          })
          .finally(db.close.bind(db));
      })
      .catch(function(err) {
        console.error("ERROR", err);
      });