loopback-connector-transactions-mongodb

The official MongoDB connector for the LoopBack framework.

Installation

In your application root directory, enter this command to install the connector:

npm install loopback-connector-transactions-mongodb --save

This installs the module from npm and adds it as a dependency to the application's package.json file.

If you create a MongoDB data source using the data source generator as described below, you don't have to do this, since the generator will run npm install for you.

Supported versions

Starting from the version 6.0.0, this connector is no longer compatible with LoopBack 3. Please use the latest 5.x version in your LoopBack 3 applications.

This module adopts the Module Long Term Support (LTS) policy, with the following End Of Life (EOL) dates:

Version	Status	Published	EOL	LoopBack	Juggler
6.x	Current	Mar 2021	Apr 2023 (minimum)	4	4.x
5.x	Active LTS	Jun 2019	Apr 2023	3, 4	3.x, 4.x
4.x	Maintenance LTS	Nov 2018	Apr 2021	3, 4	3.x, 4.x

Creating a MongoDB data source

For LoopBack 4 users, use the LB4 Command-line interface to generate a DataSource with MongoDB connector to your LB4 application. Run lb4 datasource, it will prompt for configurations such as host, post, etc. that are required to connect to a MongoDB database.

After setting it up, the configuration can be found under src/datasources/<DataSourceName>.datasource.ts, which would look like this:

const config = {
  name: 'db',
  connector: 'mongodb',
  url: '',
  host: 'localhost',
  port: 27017,
  user: '',
  password: '',
  database: 'testdb',
};

If your username or password contains special characters like @, $ etc, encode the whole username or password using encodeURIComponent.

Eg: pa$$wd would become pa%24%24wd.

Connection properties

Property	Type	Description
connector	String	Connector name, either "loopback-connector-mongodb" or "mongodb".
database	String	Database name
host	String	Database host name
name	String	Name of the datasource in the app
password	String	Password to connect to database
port	Number	Database TCP port
url	String	Connection URL of form mongodb://user:password@host/db. Overrides other connection settings (see below).
user	String	Username to connect to database
authSource	String	Optional. Authentification database name. Usually "admin" value.

If you run a MongoDB with authentification (Docker's example here), you need to specify which database to authenticate against. More details can be found in MongoDB documentation on Authentification Methods. The default value is usually "admin", like in the official docker image.

NOTE: In addition to these properties, you can use additional Single Server Connection parameters supported by node-mongodb-native.

Additional properties

Property	Type	Default	Description
allowExtendedOperators	Boolean	false	Set to true to enable using MongoDB operators such as $currentDate, $inc, $max, $min, $mul, $rename, $setOnInsert, $set, $unset, $addToSet, $pop, $pullAll, $pull, $push, and $bit. See Update Operators section below
enableGeoIndexing	Boolean	false	Set to true to enable 2d sphere indexing for model properties of type GeoPoint. This allows for indexed near queries.
lazyConnect	Boolean	false	When set to true, the database instance will not be attached to the datasource and the connection is deferred. It will try to establish the connection automatically once users hit the endpoint. If the MongoDB server is offline, the app will start, however, the endpoints will not work.
disableDefaultSort	Boolean	false	Set to true to disable the default sorting behavior on id column, this will help performance using indexed columns available in MongoDB.
collation	String	N/A	Specify language-specific rules for string comparison, such as rules for letter-case and accent marks. See MongoDB documentation for details. It can also be used to create case insensitive indexes.

Setting the url property in datasource.ts

You can set the url property to a connection URL in <datasourceName>.datasources.ts to override individual connection parameters such as host, user, and password. E.g loopback:pa55w0rd@localhost:27017/testdb.

Using the mongodb+srv protocol

MongoDB supports a protocol called mongodb+srv for connecting to replica sets without having to give the hostname of every server in the replica set. To use mongodb+srv as the protocol set the protocol connection property in the datasource.json to mongodb+srv. For example:

const config = {
  name: 'db',
  connector: 'mongodb',
  host: 'myserver',
  database: 'testdb',
  protocol: 'mongodb+srv',
};

Note: the port is not specified when using the mongodb+srv protocol and will be ignored if given.

Security Considerations

MongoDB Driver allows the $where operator to pass in JavaScript to execute on the Driver which can be used for NoSQL Injection. See MongoDB: Server-side JavaScript for more on this MongoDB feature.

To protect users against this potential vulnerability, LoopBack will automatically remove the $where and mapReduce operators from a query before it's passed to the MongoDB Driver. If you need to use these properties from within LoopBack programmatically, you can disable the sanitization by passing in an options object with disableSanitization property set to true.

Example:

await PostRepository.find(
  { where: { $where: "function() { /*JS function here*/}" } },
  { disableSanitization: true }
);

Type mappings

See LoopBack 4 types (or LoopBack 3 types) for details on LoopBack's data types.

LoopBack to MongoDB types

Type conversion is mainly handled by MongoDB. See 'node-mongodb-native' for details.

Update Operators

Except the comparison and logical operators LoopBack supports in the operator list of Where filter, you can also enable MongoDB update operators for update* methods by setting the flag allowExtendedOperators to true in the datasource configuration.

Here is an example of updating the price for all the products under category furniture if their current price is lower than 100:

await productRepo.updateAll({ $max: { price: 100 }}, { category: {eq: 'furniture'} // where clause goes in here });

{% include tip.html content="you will not need the dollar sign '$' for operators in the Where clause." %}

Handling ObjectId

MongoDB uses ObjectId for its primary key, which is an object instead of a string. In queries, string values must be cast to ObjectId, otherwise they are not considered as the same value. Therefore, you might want to specify the data type of properties to enforce ObjectId coercion. Such coercion would make sure the property value converts from ObjectId-like string to ObjectId when it accesses to the database and converts ObjectId to ObjectId-like string when the app gets back the value. (An ObjectId-like string is a string that has length 12 or 24 and has the format of an ObjectId i.e /^[0-9a-fA-F]{24}$/.)

LoopBack provides two scopes to handle such coercion: per model or per property. Please check the following to see which configuration meets your requirements.

{% include important.html content="please make sure you are using loopback-connector-mongodb package version 5.2.1 or above to handle ObjectId properly." %}

• No ObjectId coercion: CRUD operations can be operated with non-ObjectId-like string or ObjectId-like string ids.

• Enforce ObjectId coercion: the property value can only be ObjectId or ObjectId-like string, otherwise it will be rejected.

Enforcing ObjectId coercion can be done by setting the flag strictObjectIDCoercion in the model definition or by specifying dataType: ObjecId in the property definition.

Model scope

This scope would do the conversion for all properties in the model.

@model({settings: {
  strictObjectIDCoercion: true
}})
export class User extends Entity {
@property({
    type: 'string',
    id: true,
  })
  id: string;
...
}

Property scope

This scope would only convert an ObjectId-like string to ObjectId with a certain property in the model.

@property({
    type: 'string',
    id: true,
    mongodb: {dataType: 'ObjectId'}
  }
  id: string;

Also notice that for RELATIONS, if the primary key/source key has set to enforce ObjectId coercion (no matter by strictObjectIDCoercion: true or dataType: 'ObjectId'). The corresponding foreign key will need to have it set as well to make sure relations work smoothly.

@model()
export class User extends Entity {
// source key
@property({
    type: 'string',
    id: true,
    mongodb: {dataType: 'ObjectId'}
  })
  id: string;
...
}

@model(// )
export class Address extends Entity {
  ...
  // foreign key
  @belongsTo(() => User,
   {}, //relation metadata goes in here
   {// property definition goes in here
    mongodb: {dataType: 'ObjectId'}
  })
  UserId: string;
}

Customize collection/field names

loopback-connector-mongodb allows you to have different collection and field names from the models. Such configurations can be added to the model definition and the property definition respectively as mongodb:{ <field>: <customValue>}. For example, the following setting would define a collection with custom name Custom_Collection_User, and it has a custom field name Custom_Name in the database:

{% include code-caption.html content="/src/models/User.model.ts" %}

@model({
  settings: {
    // model definition goes in here
    mongodb: { collection: "Custom_Collection_User" },
  },
})
export class User extends Entity {
  @property({
    type: "string",
    id: true,
    generated: true,
  })
  id: string;

  @property({
    type: "string",
    mongodb: {
      fieldName: "Custom_Name",
    },
  })
  name?: string;
}

{% include important.html content="Since in MongoDB _id is reserved for the primary key, LoopBack does not allow customization of the field name for the id property. Please use id as is. Customizing the id property would cause errors." %}

Running tests

Own instance

If you have a local or remote MongoDB instance and would like to use that to run the test suite, use the following command:

• Linux

MONGODB_HOST=<HOST> MONGODB_PORT=<PORT> MONGODB_DATABASE=<DATABASE> CI=true npm test

• Windows

SET MONGODB_HOST=<HOST> SET MONGODB_PORT=<PORT> SET MONGODB_DATABASE=<DATABASE> SET CI=true npm test

Docker

If you do not have a local MongoDB instance, you can also run the test suite with very minimal requirements.

• Assuming you have Docker installed, run the following script which would spawn a MongoDB instance on your local:

source setup.sh <HOST> <PORT> <DATABASE>

where <HOST>, <PORT> and <DATABASE> are optional parameters. The default values are localhost, 27017 and testdb respectively.

• Run the test:

npm test

Leak detection

Tests run for 100 iterations by default, but can be increased by setting the env var ITERATIONS.

make leak-detection # run 100 iterations (default)

or

ITERATIONS=1000 make leak-detection # run 1000 iterations

Running benchmarks

Benchmarks must be run on a Unix-like operating system.

make benchmarks

The results will be output in ./benchmarks/results.md.

Release notes

• 1.1.7 - Do not return MongoDB-specific _id to client API, except if specifically specified in the model definition