I have this code, I want to run all the database inserts and then disconnect from the database at the end of the script. The problem is that I need to execute the disconnect callback after the loop ends, but it's non-deterministic. So I would need to create a function for each of the loops, and then only after all those functions have completed, call the function to disconnect from mongoose/mongoDB.
Does anyone see the problem that I have with this code?
//this code is close, but not quite, since it will disconnect from mongo before doing very many inserts/saves
var mongoose = require('mongoose')
, Admin = mongoose.mongo.Admin;
var UserModel = require('../models/UserModel');
UserModel.registerSchema(mongoose);
var fs = require('fs');
var parsedJSON = JSON.parse(fs.readFileSync('../dummy_data/dummy_user_data', 'utf8'));
var system_db = mongoose.connect('mongodb://localhost:27017/local_dev_db');
function insertUsers(callback){
parsedJSON.forEach(function (item, index) {
var User = UserModel.getNewUser(system_db);
var user = new User({
username: item.username,
password: item.password,
address: item.address,
phone: item.phone,
email: item.email,
gender: item.gender,
about: item.about,
latitude: item.latitude,
longitude: item.longitude
});
user.save(function (err, result) {
if (err) {
console.log("error in player save method:", err);
}
console.log(index);
if (result) {
//console.log('Added!', result);
}
});
});
callback();
}
function disconnect(){
mongoose.disconnect();
mongoose.connection
.close(function () {
console
.log('Mongoose connection disconnected');
process.exit(0);
});
}
insertUsers(disconnect);
So the solution would be to use the async.parallel library, and only after all the functions are done, call a final callback function. However, how can I do that programmatically instead of putting a known group of functions into the async.parallel codeblock, I need to put an unknown number of functions into the aysnc.parallel codeblock. Ya seen?
Definitely can be done. Just dynamically add your functions to an array that will be passed to async.parallel:
var fs = require('fs');
var async = require('async');
var mongoose = require('mongoose'),
Admin = mongoose.mongo.Admin;
var UserModel = require('../models/UserModel');
UserModel.registerSchema(mongoose);
var parsedJSON = JSON.parse(fs.readFileSync('../dummy_data/dummy_user_data', 'utf8'));
var system_db = mongoose.connect('mongodb://localhost:27017/local_dev_db');
var insertFunctions = [];
parsedJSON.forEach(function (item, index) {
insertFunctions.push(function(callback) {
var User = UserModel.getNewUser(system_db);
var user = new User({
username: item.username,
password: item.password,
address: item.address,
phone: item.phone,
email: item.email,
gender: item.gender,
about: item.about,
latitude: item.latitude,
longitude: item.longitude
});
user.save(function (err, result) {
if (err) {
console.log("error in player save method:", err);
callback(err);
return;
}
callback(null, result);
});
});
});
function disconnect() {
mongoose.disconnect();
mongoose.connection
.close(function () {
console
.log('Mongoose connection disconnected');
process.exit(0);
});
}
//First parameter is the array of functions to run in parallel,
// second parameter is the callback function
async.parallel(insertFunctions, disconnect);
In this particular case, async.each() actually fits better than async.parallel(). async.each() is parallel while async.eachSeries() is not. Here is the code:
function insertUsers(callback){
var User = UserModel.getNewUser(system_db);
async.each(parsedJSON, function (item, eachCb) {
var user = new User({
username: item.username,
password: item.password,
address: item.address,
phone: item.phone,
email: item.email,
gender: item.gender,
about: item.about,
latitude: item.latitude,
longitude: item.longitude
});
user.save(function (err, result) {
if (err) {
console.log("error in player save method:", err);
}
console.log(index);
if (result) {
//console.log('Added!', result);
}
eachCb(); // if calling with eachCb(err), async.each()
// will not continue the rest of the items
// in case of error occurs
});
}, function(err) {
callback(); // done with all user.save() calls
});
}