migrate-mongo

migrate-mongo is a database migration tool for MongoDB running in Node.js

Installation

$ npm install -g migrate-mongo

CLI Usage

$ migrate-mongo
Usage: migrate-mongo [options] [command]


  Commands:

    init                  initialize a new migration project
    create [description]  create a new database migration with the provided description
    up [options]          run all unapplied database migrations
    down [options]        undo the last applied database migration
    status [options]      print the changelog of the database

  Options:

    -h, --help     output usage information
    -V, --version  output the version number

Basic Usage

Initialize a new project

Make sure you have Node.js 10 (or higher) installed.

Create a directory where you want to store your migrations for your mongo database (eg. 'albums' here) and cd into it

$ mkdir albums-migrations
$ cd albums-migrations

Initialize a new migrate-mongo project

$ migrate-mongo init
Initialization successful. Please edit the generated migrate-mongo-config.js file

The above command did two things:

1. create a sample 'migrate-mongo-config.js' file and
2. create a 'migrations' directory

Edit the migrate-mongo-config.js file. An object or promise can be returned. Make sure you change the mongodb url:

// In this file you can configure migrate-mongo

module.exports = {
  mongodb: {
    // TODO Change (or review) the url to your MongoDB:
    url: "mongodb://localhost:27017",

    // TODO Change this to your database name:
    databaseName: "YOURDATABASENAME",

    options: {
      useNewUrlParser: true // removes a deprecation warning when connecting
      //   connectTimeoutMS: 3600000, // increase connection timeout to 1 hour
      //   socketTimeoutMS: 3600000, // increase socket timeout to 1 hour
    }
  },

  // The migrations dir, can be an relative or absolute path. Only edit this when really necessary.
  migrationsDir: "migrations",

  // The mongodb collection where the applied changes are stored. Only edit this when really necessary.
  changelogCollectionName: "changelog",

  // The file extension to create migrations and search for in migration dir 
  migrationFileExtension: ".js",

  // Enable the algorithm to create a checksum of the file contents and use that in the comparison to determin
  // if the file should be run.  Requires that scripts are coded to be run multiple times.
  useFileHash: false
};

Alternatively, you can also encode your database name in the url (and leave out the databaseName property):

        url: "mongodb://localhost:27017/YOURDATABASE",

Creating a new migration script

To create a new database migration script, just run the migrate-mongo create [description] command.

For example:

$ migrate-mongo create blacklist_the_beatles
Created: migrations/20160608155948-blacklist_the_beatles.js

A new migration file is created in the 'migrations' directory:

module.exports = {
  up(db, client) {
    // TODO write your migration here. Return a Promise (and/or use async & await).
    // See https://github.com/seppevs/migrate-mongo/#creating-a-new-migration-script
    // Example:
    // return db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: true}});
  },

  down(db, client) {
    // TODO write the statements to rollback your migration (if possible)
    // Example:
    // return db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: false}});
  }
};

Edit this content so it actually performs changes to your database. Don't forget to write the down part as well. The db object contains the official MongoDB db object The client object is a MongoClient instance (which you can omit if you don't use it).

There are 3 options to implement the up and down functions of your migration:

1. Return a Promises
2. Use async-await
3. Call a callback (DEPRECATED!)

Always make sure the implementation matches the function signature:

• function up(db, client) { /* */ } should return Promise
• async function up(db, client) { /* */ } should contain await keyword(s) and return Promise
• function up(db, client, next) { /* */ } should callback next

Example 1: Return a Promise

module.exports = {
  up(db) {
    return db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: true}});
  },

  down(db) {
    return db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: false}});
  }
};

Example 2: Use async & await

Async & await is especially useful if you want to perform multiple operations against your MongoDB in one migration.

module.exports = {
  async up(db) {
    await db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: true}});
    await db.collection('albums').updateOne({artist: 'The Doors'}, {$set: {stars: 5}});
  },

  async down(db) {
    await db.collection('albums').updateOne({artist: 'The Doors'}, {$set: {stars: 0}});
    await db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: false}});
  },
};

Example 3: Call a callback (deprecated)

Callbacks are supported for backwards compatibility. New migration scripts should be written using Promises and/or async & await. It's easier to read and write.

module.exports = {
  up(db, callback) {
    return db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: true}}, callback);
  },

  down(db, callback) {
    return db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: false}}, callback);
  }
};

Overriding the sample migration

To override the content of the sample migration that will be created by the create command, create a file sample-migration.js in the migrations directory.

Checking the status of the migrations

At any time, you can check which migrations are applied (or not)

$ migrate-mongo status
┌─────────────────────────────────────────┬────────────┐
│ Filename                                │ Applied At │
├─────────────────────────────────────────┼────────────┤
│ 20160608155948-blacklist_the_beatles.js │ PENDING    │
└─────────────────────────────────────────┴────────────┘

Migrate up

This command will apply all pending migrations

$ migrate-mongo up
MIGRATED UP: 20160608155948-blacklist_the_beatles.js

If an an error occurred, it will stop and won't continue with the rest of the pending migrations

If we check the status again, we can see the last migration was successfully applied:

$ migrate-mongo status
┌─────────────────────────────────────────┬──────────────────────────┐
│ Filename                                │ Applied At               │
├─────────────────────────────────────────┼──────────────────────────┤
│ 20160608155948-blacklist_the_beatles.js │ 2016-06-08T20:13:30.415Z │
└─────────────────────────────────────────┴──────────────────────────┘

Migrate down

With this command, migrate-mongo will revert (only) the last applied migration

$ migrate-mongo down
MIGRATED DOWN: 20160608155948-blacklist_the_beatles.js

If we check the status again, we see that the reverted migration is pending again:

$ migrate-mongo status
┌─────────────────────────────────────────┬────────────┐
│ Filename                                │ Applied At │
├─────────────────────────────────────────┼────────────┤
│ 20160608155948-blacklist_the_beatles.js │ PENDING    │
└─────────────────────────────────────────┴────────────┘

Advanced Features

Using a custom config file

All actions (except init) accept an optional -f or --file option to specify a path to a custom config file. By default, migrate-mongo will look for a migrate-mongo-config.js config file in of the current directory.

Example:

$ migrate-mongo status -f '~/configs/albums-migrations.js'
┌─────────────────────────────────────────┬────────────┐
│ Filename                                │ Applied At │
├─────────────────────────────────────────┼────────────┤
│ 20160608155948-blacklist_the_beatles.js │ PENDING    │
└─────────────────────────────────────────┴────────────┘

Using npm packages in your migration scripts

You can use use Node.js modules (or require other modules) in your migration scripts. It's even possible to use npm modules, just provide a package.json file in the root of your migration project:

$ cd albums-migrations
$ npm init --yes

Now you have a package.json file, and you can install your favorite npm modules that might help you in your migration scripts. For example, one of the very useful promise-fun npm modules.

Using ESM (ECMAScript Modules) instead of CommonJS

Since migrate-mongo 7.0.0, it's possible to use ESM instead of CommonJS.

Using ESM when initializing a new project

Pass the -m esm option to the init action:

$ migrate-mongo init -m esm

It's also required to have package.json file in the root of your project with "type": "module". Create a new package.json file:

$ npm init --yes

Then edit this package.json file, and add:

"type": "module"

When you create migration files with migrate-mongo create, they will be prepared for you in ESM style.

Please note that CommonJS is still the default module loading system.

Using MongoDB's Transactions API

You can make use of the MongoDB Transaction API in your migration scripts.

Note: this requires both:

• MongoDB 4.0 or higher
• migrate-mongo 7.0.0 or higher

migrate-mongo will call your migration up and down function with a second argument: client. This client argument is an MongoClient instance, it gives you access to the startSession function.

Example:

module.exports = {
  async up(db, client) {
    const session = client.startSession();
    try {
        await session.withTransaction(async () => {
            await db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: true}}, {session});
            await db.collection('albums').updateOne({artist: 'The Doors'}, {$set: {stars: 5}}, {session});
        });
    } finally {
      await session.endSession();
    }
  },

  async down(db, client) {
    const session = client.startSession();
    try {
        await session.withTransaction(async () => {
            await db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: false}}, {session});
            await db.collection('albums').updateOne({artist: 'The Doors'}, {$set: {stars: 0}}, {session});
        });
    } finally {
      await session.endSession();
    }
  },
};

Using a file hash algorithm to enable re-running updated files

There are use cases where it may make sense to not treat scripts as immutable items. An example would be a simple collection with lookup values where you just can wipe and recreate the entire collection all at the same time.

useFileHash: true

Set this config value to will enable tracking a hash of the file contents and will run a file with the same name again as long as the file contents have changes. Setting this flag changes the behavior for every script and if this is enabled each script needs to be written in a manner where it can be re-run safefly. A script of the same name and hash will not be executed again, only if the hash changes.

Now the status will also include the file hash in the output

┌────────────────────────────────────────┬──────────────────────────────────────────────────────────────────┬──────────────────────────┐
│ Filename                               │ Hash                                                             │ Applied At               │
├────────────────────────────────────────┼──────────────────────────────────────────────────────────────────┼──────────────────────────┤
│ 20160608155948-blacklist_the_beatles.js│ 7625a0220d552dbeb42e26fdab61d8c7ef54ac3a052254588c267e42e9fa876d │ 2021-03-04T15:40:22.732Z │
└────────────────────────────────────────┴──────────────────────────────────────────────────────────────────┴──────────────────────────┘

Version

To know which version of migrate-mongo you're running, just pass the version option:

$ migrate-mongo version

API Usage

const {
  init,
  create,
  database,
  config,
  up,
  down,
  status
} = require('migrate-mongo');

init() → Promise

Initialize a new migrate-mongo project

await init();

The above command did two things:

1. create a sample migrate-mongo-config.js file and
2. create a migrations directory

Edit the migrate-mongo-config.js file. Make sure you change the mongodb url.

create(description) → Promise

For example:

const fileName = await create('blacklist_the_beatles');
console.log('Created:', fileName);

A new migration file is created in the migrations directory.

database.connect() → Promise<{db: MongoDb, client: MongoClient}>

Connect to a mongo database using the connection settings from the migrate-mongo-config.js file.

const { db, client } = await database.connect();

config.read() → Promise

Read connection settings from the migrate-mongo-config.js file.

const mongoConnectionSettings = await config.read();

config.set(yourConfigObject)

Tell migrate-mongo NOT to use the migrate-mongo-config.js file, but instead use the config object passed as the first argument of this function. When using this feature, please do this at the very beginning of your program.

Example:

const { config, up } = require('../lib/migrate-mongo');

const myConfig = {
    mongodb: {
        url: "mongodb://localhost:27017/mydatabase",
        options: { useNewUrlParser: true }
    },
    migrationsDir: "migrations",
    changelogCollectionName: "changelog",
    migrationFileExtension: ".js"
};

config.set(myConfig);

// then, use the API as you normally would, eg:
await up();

up(MongoDb, MongoClient) → Promise>

Apply all pending migrations

const { db, client } = await database.connect();
const migrated = await up(db, client);
migrated.forEach(fileName => console.log('Migrated:', fileName));

If an an error occurred, the promise will reject and won't continue with the rest of the pending migrations.

down(MongoDb, MongoClient) → Promise>

Revert (only) the last applied migration

const { db, client } = await database.connect();
const migratedDown = await down(db, client);
migratedDown.forEach(fileName => console.log('Migrated Down:', fileName));

status(MongoDb) → Promise>

Check which migrations are applied (or not.

const { db } = await database.connect();
const migrationStatus = await status(db);
migrationStatus.forEach(({ fileName, appliedAt }) => console.log(fileName, ':', appliedAt));

client.close() → Promise

Close the database connection

const { db, client } = await database.connect();
await client.close();