mongodb-migrator

Table of Contents

• Installation
• CLI usage
  • Configuration
    • Creating Migrations
    • Sample migration file
  • Running migrations
  • Check for new migrations
• Programmatic usage
  • Using Migrator

Installation

$ npm install -g mongodb-migrator

CLI usage

The package installs a single CLI executable — mdbmigrator.

When installing locally to your project this executable can be found at ./node_modules/.bin/mdbmigrator.

When installing globally the executable should automatically become accessible on your PATH.

Configuration

The configuration can be passed as a file (js or json):

// myconfig.json
{
  "mongourl": "mongodb://localhost:27017/migrations",
  "host": "localhost",
  "port": 27017,
  "db": "migrations",
  "user": "username",
  "password": "secret_password",
  "collection": "migrations_track",
  "directory": "migrations"
}

  mdbmigrator --config myconfig.json create mynewmigration

or cli arguments:

  mdbmigrator --host 127.0.0.1 --port 27017 --db migrations create newmigrationname

Creating Migrations

The app simplifies creating migration stubs by providing a command

$ mdbmigrator create 'migration name'

This creates file migration-name.js inside of the directory defined in the configuration file.

Sample migration file

  module.exports = {
    name: 'migration name',
    after: null
    up: function (db, cb) {
      cb();
    },
    down: function (db, cb) {
      cb();
    }
  }

Where

• migration name — a unique name for migration.
• up — a function used for forward migration.
• down — a function used for backward migration.

Migration functions

The up and down functions take for two parameters db - mongodb connection and callback cb

up: function(db, cb) {
  db.collection('users').insertOne({name:"firstadmin",pass:"very_secure_password"}, function (err, result) {
    if(err) return cb(err);
    console.log("all done");
    cb();
  });
}

Running migrations

Applying all new migrations from the directory (specified in Configuration) by calling

$ mdbmigrator apply

Rollbacks are automatically called in the reverse order when an error occurs.

The library only runs migrations that:

1. have up function defined,
2. were not ran before against this database.
3. were rollback at any moment

Successfully applied migrations are recorded in the collection specified in Configuration and successfully canceled migrations remove the record from the collection.

The migration process is stopped instantly if some migration fails (returns error in its callback), then beginning roll back process.

Check for new migrations

$ mdbmigrator check

Programmatic usage

The library also supports programmatic usage.

Start with require'ing it:

var MongoMigrator = require('mongodb-migrator');
 
var migrator = new MongoMigrator(options);
 

Using migrator

Next, you can use migrator instance as was described before:

 
// Load all migrations
var migrationsArray = migrator.loadMigrations();
 
// Check for circularity's and count new migrations
migrator.check();
 
// Apply new migrations
migrator.apply();