fifo_connections.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var assert = require('assert')

console.log('\n===========');
console.log('    mongoose version: %s', mongoose.version);
console.log('========\n\n');

mongoose.connect('localhost', 'testing_fifo', { server: { poolSize: 1 }}); // change poolSize to > 1
mongoose.connection.on('error', function () {
  console.error('connection error', arguments);
});

var schema = new Schema({
    name: String
});

var A = mongoose.model('A', schema);

mongoose.connection.on('open', function () {
  console.log('opened');
  mongoose.set('debug', true);
  A.create({ name: 'fifo1' }, { name: 'fifo2' }, function (err) {
    if (err) return done(err);
    A.$where('for (var i = 0; i < 5000000; i++) {}; return true').exec(function (err) {
      // this blocks other ops if poolSize of 1
      console.log('where returned');
    });
    A.find({}).exec(function (err, docs) {
      // will wait for $where to complete
      console.error(arguments);
      done()
    })
  });
});

function done (err) {
  if (err) console.error(err.stack);
  mongoose.connection.db.dropDatabase(function () {
    mongoose.connection.close();
  });
}