Mongo Library Storage

There is an implementation of the ILibraryStorage interface that stores the metadata and files of libraries in MongoDB. As the library files should never be above the limit of MongoDB's binary data fields (~5 MB), we we don't use GridFS. You can find the storage class in /packages/h5p-mongos3/src/MongoLibraryStorage.ts.

There is another very similar storage class MongoS3LibraryStorage, which uses S3 to store library files and might be a better fit if you have to storage very large library files (none of the normal content types do!) or if you need to reduce load on your MongoDB server.

Dependencies

The implementation depends on this NPM package:

• mongodb

You must add it manually to your application using npm install mongodb!

Usage

You must import the storage implementation:

import { MongoLibraryStorage, initMongo } from '@lumieducation/h5p-mongos3';

or in classic JS style:

const { MongoLibraryStorage, initMongo } = require('@lumieduation/h5p-mongos3');

Initialize the storage implementation like this:

const storage = new MongoLibraryStorage(
    (
        await initMongo(
            'mongodb://127.0.0.1:27017', // optional if env. variable is set
            'testdb1', // optional if env. variable is set
            'root', // optional if env. variable is set
            'h5pnodejs' // optional if env. variable is set
        )
    ).collection('h5p')
);
await storage.createIndexes();

You can safely call createIndexes() every time you start you application, as MongoDB checks if indexes already exist before it creates new ones.

Notes

• The function initMongo creates a MongoDB client using the mongodb npm package.
• You can pass credentials and other configuration values to initMongo through the function parameters. Alternatively you can use these environment variables instead of using the function parameters:

  • MONGODB_URL

  • MONGODB_DB

  • MONGODB_USER

  • MONGODB_PASSWORD

• You can change the MongoDB collection name h5p to any name you want. If the collection doesn't exist yet, it will be automatically created.

• To achieve greater configurability, you can decide not to use initMongo and instantiate the required clients yourself.

Using MongoLibraryStorage in the example

The example Express application can be configured to use the MongoDB library storage by setting the environment variables from above and these additional variables:

• LIBRARYSTORAGE=mongo

• LIBRARY_MONGO_COLLECTION

An example call would be:

MONGODB_URL="mongodb://127.0.0.1:27017" MONGODB_DB=testdb1 MONGODB_USER=root MONGODB_PASSWORD=h5pnodejs LIBRARYSTORAGE=mongo LIBRARY_MONGO_COLLECTION=h5p npm start

Migrations

The method MongoLibraryStorage.migrate can be called when you move to a new major version of MongoLibraryStorage:

await storage.migrate(/*from major version*/ 9, /*to major version*/ 10);

Calling this method will migrate the MongoDB collection data. Note that there is no versioning of the MongoDB collection inside MongoDB. It's your job to decide when to call the migration!

Currently supported migrations

• v9 to v10: Introduces new field ubername that has the same value as _id

Developing and testing

There are automated tests in /test/implementation/db/MongoLibraryStorage.test.ts. However, these tests will not be called automatically when you run npm run test or other test calls. The reason is that the tests require a running MongoDB and S3 instance and thus need more extensive setup. To manually execute the tests call npm run test:h5p-mongos3.

To quickly get a functioning MongoDB instance, you can use the Docker Compose file in the scripts directory like this (you obviously must install Docker and Docker Compose first):

docker-compose -f scripts/mongo-s3-docker-compose.yml up -d

This will start a MongoDB server and MinIO instance in containers. Note that the instances will now be started when your system boots. To stop them from doing this and completely wipe all files from your system, execute:

docker-compose -f scripts/mongo-s3-docker-compose.yml down -v