Memory connector - Loopback Next

Overview

LoopBack's built-in memory connector enables you to test your application without connecting to an actual persistent data source such as a database. Although the memory connector is very well tested it is not suitable for production.

The memory connector supports:

Standard query and create, read, update, and delete operations, so you can test models against an in-memory data source.

{% include important.html content=" The memory connector is designed for development and testing of a single-process application without setting up a database. It cannot be used in a cluster as the worker processes will have their own isolated data not shared in the cluster.

You can persist data between application restarts using the file property. See Data persistence for more information. " %}

Limitations

The connector does not implement transactions. Hence, transactions will fail with an error.

Memory connector properties

<table> <tbody> <tr> <th>Property</th> <th>Type</th> <th>Description</th> </tr> <tr> <td>name</td> <td>String</td> <td>Name by which you refer to the data source.</td> </tr> <tr> <td>connector</td> <td>String</td> <td>Must be "memory" to use the memory connector.</td> </tr> <tr> <td>localStorage</td> <td>String</td> <td> <b>Not recommended.</b> Path to the browser Local Storage. This is kept for legacy reasons and may be removed in a future release. </td> </tr> <tr> <td>file</td> <td>String</td> <td> <p>Path to file where the connector will store data, relative to application root directory.</p> <p>NOTE: The connector will create the file if necessary, but the directory containing the file must exist.</p> </td> </tr> </tbody> </table>

{% include important.html content=" If you specify the file property, the connector will save data there that will persist when you restart the application. Otherwise, the memory connector does not persist data after an application stops. " %}

Data persistence

By default, data in the memory connector are transient. When an application using the memory connector exits, all model instances are lost. To maintain data across application restarts, specify a JSON file in which to store the data with the file property when creating the data source.

The simplest way to do this is by editing src/datasources/[datasource name].datasource.ts; for example:

{% include code-caption.html content="src/datasources/db.datasource.ts" %}

diff

import {inject} from '@loopback/core';
import {juggler} from '@loopback/repository';

const config = {
  name: 'db',
  connector: 'memory',
  localStorage: '',
+ file: './data/db.json',
- file: '',
};

export class DbDataSource extends juggler.DataSource {
  static dataSourceName = 'db';
  static readonly defaultConfig = config;

  constructor(
    @inject('datasources.config.db', {optional: true})
    dsConfig: object = config,
  ) {
    super(dsConfig);
  }
}