Migrator

The migrator is a framework agnostic migration tool for Node.JS. The tool itself is not specifically related to databases but basically provides a clean API for running and rolling back tasks.

Persistence

In order to keep track of already executed tasks, migrator logs successfully executed migrations. This is done in order to allow rollbacks of tasks. There are multiple storage presets available, from which you can choose. Adding a custom is super simple as well.

Storages

JSON

Using the json storage will create a JSON file which will contain an array with all the executed migrations. You can specify the path to the file. The default for that is migrator.json in the working directory of the process.

Options

{
  // The path to the json storage.
  // Defaults to process.cwd() + '/migrations.json';
  path: process.cwd() + '/db/sequelize-meta.json'
}

Sequelize

Using the sequelize storage will create a table in your database called SequelizeMeta containing an entry for each executed migration. You will have to pass a configured instance of Sequelize. Optionally you can specify the table name.

Legacy Sequelize

Using the legacy storage will create the obsolete SequelizeMeta table structure which contains information about executed migration runs which contains a from and a to column. You will have to pass a configured instance of Sequelize. Please note, that using this storage is not recommended.

Custom

In order to use a custom storage, you can create and publish a module which has to fulfill the following API. You can just pass the name of the module to the configuration and migrator will require it accordingly. The API that needs to be exposed looks like this:

var Bluebird = require('bluebird');
var redefine = require('redefine');

module.exports = redefine.Class({
  constructor: function (options) {
    this.options = options;
    this.options.storageOptions = _.extend({
      option1: 'defaultValue1'
    }, this.options.storageOptions)
  },

  logMigration: function (migrationName) {
    return new Bluebird(function (resolve, reject) {
      // This function logs a migration as executed.
      // It will get called once a migration was
      // executed successfully.
    });
  },

  unlogMigration: function (migrationName) {
    return new Bluebird(function (resolve, reject) {
      // This function removes a previously logged migration.
      // It will get called once a migration has been reverted.
    });
  },

  executed: function () {
    return new Bluebird(function (resolve, reject) {
      // This function lists the names of the logged
      // migrations. It will be used to calculate
      // pending migrations. The result has to be an
      // array with the names of the migration files.
    });
  }
});

Migrations

Migrations are basically files that describe ways of executing and reverting tasks. In order to allow asynchronicity, tasks have return a Promise object which provides a then method.

Format

A migration file ideally contains an up and a down method, which represent a function which achieves the task and a function that reverts a task. The file could look like this:

'use strict';

var Bluebird = require('bluebird');

module.exports = {
  up: function () {
    return new Bluebird(function (resolve, reject) {
      // Describe how to achieve the task.
      // Call resolve/reject at some point.
    });
  },

  down: function () {
    return new Bluebird(function (resolve, reject) {
      // Describe how to revert the task.
      // Call resolve/reject at some point.
    });
  }
};

Usage

Installation

The migrator is available on npm:

npm install sequelize-migrator

API

The basic usage of migrator is as simple as that:

var Migrator = require('sequelize-migrator');
var migrator = new Migrator({});

migrator.someMethod().then(function (result) {
  // do something with the result
});

Executing migrations

The execute method is a general purpose function that runs for every specified migrations the respective function.

migrator.execute({
  migrations: ['some-id', 'some-other-id'],
  method: 'up'
}).then(function (migrations) {
  // "migrations" will be an Array of all executed/reverted migrations.
});

Getting all pending migrations

You can get a list of pending/not yet executed migrations like this:

migrator.pending().then(function (migrations) {
  // "migrations" will be an Array with the names of
  // pending migrations.
});

Getting all executed migrations

You can get a list of already executed migrations like this:

migrator.executed().then(function (migrations) {
  // "migrations" will be an Array of already executed migrations.
});

Executing pending migrations

The up method can be used to execute all pending migrations.

migrator.up().then(function (migrations) {
  // "migrations" will be an Array with the names of the
  // executed migrations.
});

It is also possible to pass the name of a migration in order to just run the migrations from the current state to the passed migration name.

migrator.up({ to: '20141101203500-task' }).then(function (migrations) {});

Running specific migrations while ignoring the right order, can be done like this:

migrator.up({ migrations: ['20141101203500-task', '20141101203501-task-2'] });

There are also shorthand version of that:

migrator.up('20141101203500-task'); // Runs just the passed migration
migrator.up(['20141101203500-task', '20141101203501-task-2']);

Running

Reverting executed migration

The down method can be used to revert the last executed migration.

migrator.down().then(function (migration) {
  // "migration" will the name of the reverted migration.
});

It is possible to pass the name of a migration until which the migrations should be reverted. This allows the reverse of multiple migrations at once.

migrator.down({ to: '20141031080000-task' }).then(function (migrations) {
  // "migrations" will be an Array with the names of all reverted migrations.
});

Reverting specific migrations while ignoring the right order, can be done like this:

migrator.down({ migrations: ['20141101203500-task', '20141101203501-task-2'] });