migrate-mongo

   

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

Requirements

- Node.js >=20.0.0
- MongoDB 4.x, 5.x, 6.x, or 7.x

Installation

```bash
$ npm install -g migrate-mongo
``

CLI Usage

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

Options:
-V, --version output the version number
-h, --help display help for command

Commands:
init [options] initialize a new migration project
create [options] [description] create a new database migration with the provided description
up [options] run all pending database migrations
down [options] undo the last applied database migration
status [options] print the changelog of the database
help [command] display help for command
``

Basic Usage

$3

Make sure you have Node.js 20 (or higher) installed.

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

Initialize a new migrate-mongo project
``bash
$ migrate-mongo init
Initialization successful. Please edit the generated migrate-mongo-config.js file
``

By default, this creates a CommonJS project. To use ES modules instead:
``bash
$ migrate-mongo init -m esm
``

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:
``javascript
// In this file you can configure migrate-mongo

const config = {
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 (not needed in mongodb driver 4.x+)
// useUnifiedTopology: true, // removes a deprecating warning when connecting (not needed in mongodb driver 4.x+)
// 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 mongodb collection where the lock will be created.
lockCollectionName: "changelog_lock",

// The value in seconds for the TTL index that will be used for the lock. Value of 0 will disable the feature.
lockTtl: 0,

// 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 determine
// if the file should be run. Requires that scripts are coded to be run multiple times.
useFileHash: false,

// Don't change this, unless you know what you're doing
moduleSystem: 'commonjs',
};

module.exports = config;
``

Alternatively, you can also encode your database name in the url (and leave out the databaseName property):
``
url: "mongodb://localhost:27017/YOURDATABASE",
``

$3


To create a new database migration script, just run the ``migrate-mongo create [description]`` command (Make sure you are in the same directory as the migrations folder. albums here).

For example:
``bash
$ migrate-mongo create blacklist_the_beatles
Created: migrations/20160608155948-blacklist_the_beatles.js
``

A new migration file is created in the 'migrations' directory:
``javascript
module.exports = {
/**
* @param db {import('mongodb').Db}
* @param client {import('mongodb').MongoClient}
* @returns {Promise}
*/
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}});
},

/**
* @param db {import('mongodb').Db}
* @param client {import('mongodb').MongoClient}
* @returns {Promise}
*/
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 2 ways to implement the up and down functions of your migration:
1. Return a Promise
2. Use async-await (recommended)

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

#### Example 1: Return a Promise
``javascript
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 (recommended)
Async & await is especially useful if you want to perform multiple operations against your MongoDB in one migration.

``javascript
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}});
},
};
``

#### 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.

$3

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

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

``




$3


This command will apply all pending migrations
``bash
$ 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:
``bash
$ migrate-mongo status
┌─────────────────────────────────────────┬──────────────────────────┐
│ Filename │ Applied At │
├─────────────────────────────────────────┼──────────────────────────┤
│ 20160608155948-blacklist_the_beatles.js │ 2016-06-08T20:13:30.415Z │
└─────────────────────────────────────────┴──────────────────────────┘
``

$3

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

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

#### Migrate down all scripts from a same migration
With the flag -b (--block), migrate-mongo will revert all scripts of the last migration.
``bash
$ migrate-mongo down -b
``

Advanced Features

$3


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:

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

$3


All actions (except `init`) accept an optional ``--migrations-dir`` option to specify a path to a custom migrations directory. This will override the migrationsDir property in the config file.

By default, migrate-mongo will look for a ``migrations`` directory in the current directory.

#### Example:

``bash
$ migrate-mongo create blacklist_the_doors --migrations-dir ~/migrations/albums
Created: ~/migrations/albums/20160608155949-blacklist_the_doors.js
``




$3


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:

``bash
$ 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.




$3

Since migrate-mongo 9.0.0, 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:
``bash
$ 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:
``bash
$ npm init --yes
``

Then edit this package.json file, and add:
``bash
"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.

$3

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:

``javascript
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();
}
},
};
``

$3

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.

`javascript
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

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

`

$3


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

``bash
$ migrate-mongo version
``

API Usage

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

$3

Initialize a new migrate-mongo project
`javascript
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.

$3

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

A new migration file is created in the migrations directory.

$3

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

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

$3

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

`javascript
const mongoConnectionSettings = await config.read();
`

$3

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

const myConfig = {
mongodb: {
url: "mongodb://localhost:27017/mydatabase",
// options: { useNewUrlParser: true } // Not needed in mongodb driver 4.x+
},
migrationsDir: "migrations",
changelogCollectionName: "changelog",
migrationFileExtension: ".js"
};

config.set(myConfig);

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

$3

Apply all pending migrations

`javascript
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.

$3

Revert (only) the last applied migration

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

$3

Check which migrations are applied (or not.

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

$3

Close the database connection

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