LTIJS Firestore plugin.

Introduction

This package allows LTIJS to work with Firestore instead of MongoDB.

Installation

npm install @examind/ltijs-firestore

Import package (TypeScript and ES Modules):

import { Firestore } from '@examind/ltijs-firestore';

Import package (CommonJS):

const { Firestore } = require('@examind/ltijs-firestore');

Register the plugin during LTIJS setup:

lti.setup(
  'LTIKEY',
  { plugin: new Firestore() }
);

The Firestore constructor accepts an options object with the following property:

• collectionPrefix: A custom prefix to prepend to all collection paths. Defaults to empty string.
  • Example 1: ltijs- will create collections 'ltijs-accsesstoken', 'ltijs-platforms', etc.
  • Example 2: ltijs/index/ will create subcollections 'ltijs/index/accesstoken', 'ltijs/index/platforms', etc.

Example with options:

lti.setup(
  'LTIKEY',
  { plugin: new Firestore({collectionPrefix: 'ltijs-'}) }
);

Firestore Authentication

The firebase-admin library that's used in this package looks for a LTIJS_APPLICATION_CREDENTIALS environment variable. That environment variable needs to point to a GCP Service Account key with access to Firestore. For simplicity, you can use the Firebase Admin SDK private key from Firebase Console:

• Select your project from Firebase Console
• Go to Project Settings -> Service accounts, then download a new private key:

Save that file somewhere (e.g. ./service-account.json), then point LTIJS_APPLICATION_CREDENTIALS to that file. If you use dotenv, then your .env file will look like this:

LTIJS_APPLICATION_CREDENTIALS=./service-account.json

If you prefer to hard code the environment variable inside a Node.js file, you can do this:

process.env.LTIJS_APPLICATION_CREDENTIALS = './service-account.json'

Notes:

• Specifying the LTIJS_APPLICATION_CREDENTIALS environment variable is recommended, but if not available, firebase-admin will also look for a GOOGLE_APPLICATION_CREDENTIALS environment variable.
• When using LTIJS_APPLICATION_CREDENTIALS, make sure the environment variable is set before you import @examind/ltijs-firestore. Example using dotenv:

import { config } from 'dotenv';
if (process.env.NODE_ENV !== 'production') config();
import { Firestore } from '@examind/ltijs-firestore';

The following will also work if you're using dotenv unconditionally:

import 'dotenv/config';
import { Firestore } from '@examind/ltijs-firestore';

• When using GOOGLE_APPLICATION_CREDENTIALS, it's not necessary to set the environment variable before you import @examind/ltijs-firestore, as firebase-admin will lazy load the credentials. For example, this will work:

import { config } from 'dotenv';
import { Firestore } from '@examind/ltijs-firestore';
if (process.env.NODE_ENV !== 'production') config();

• If running this inside of a GCP server (e.g. GCP Compute Engine, GCP Cloud Function, or GCP Cloud Run), you may omit the LTIJS_APPLICATION_CREDENTIALS environment variable, as GOOGLE_APPLICATION_CREDENTIALS will be set automatically using the default service account.

Principle of Least Privilege

As an alternative to using the Firebase Admin SDK private key, you can choose to only grant the necessary permissions to @examind/ltijs-firestore. To do this, create a custom service account with only the Cloud Datastore User role and use its key instead.

Purging Stale Documents

The default detabase provider of LTIJS uses MongoDB as its storage layer and it's configured to automatically purge stale documents. To set up the same behavior in Firestore, we'll use one of 2 strategies depending on which version of @examind/ltijs-firestore you're using.

@examind/ltijs-firestore v2+

@examind/litjs-firestore@2+ sets expiresAt on the following documents:

• accesstoken
• contexttoken
• idtoken
• nonce
• state

Use this field set up Firestore TTL Policies to auto-purge stale documents. You only need to set this up once.

Using gcloud, substitute your project ID for {project_id} and execute the following commands. Warning, this will take a while.

gcloud firestore fields ttls update expiresAt --collection-group=accesstoken --enable-ttl --project={project_id}
gcloud firestore fields ttls update expiresAt --collection-group=contexttoken --enable-ttl --project={project_id}
gcloud firestore fields ttls update expiresAt --collection-group=idtoken --enable-ttl --project={project_id}
gcloud firestore fields ttls update expiresAt --collection-group=nonce --enable-ttl --project={project_id}
gcloud firestore fields ttls update expiresAt --collection-group=state --enable-ttl --project={project_id}

To ensure that everything worked correctly, you can list all your TTL policies:

gcloud firestore fields ttls list --project={project_id}

Upgrade Guide

When upgrading from v1.1+, previous TTL policies will need to be deleted as Firestore only allows 1 TTL policy per collection group. You'll also want to amend the existing documents in the database so they include expiresAt fields.

Delete previous TTL policies:

gcloud firestore fields ttls update age1HourAt --collection-group=accesstoken --disable-ttl --project={project_id}
gcloud firestore fields ttls update age24HoursAt --collection-group=contexttoken --disable-ttl --project={project_id}
gcloud firestore fields ttls update age24HoursAt --collection-group=idtoken --disable-ttl --project={project_id}
gcloud firestore fields ttls update age2MinutesAt --collection-group=nonce --disable-ttl --project={project_id}
gcloud firestore fields ttls update age10MinutesAt --collection-group=state --disable-ttl --project={project_id}

To add deletedAt to existing documents, use firebase-admin to run the following script.
You'll need to set the GOOGLE_APPLICATION_CREDENTIALS environment variable to point to a gcloud auth key for this to work: export GOOGLE_APPLICATION_CREDENTIALS='./my-gcloud-auth-key.json'

const { initializeApp } = require('firebase-admin/app');
const { getFirestore } = require('firebase-admin/firestore');

const app = initializeApp({ projectId: 'my-project-id' });
const db = getFirestore(app);

// Set this if you're using a collection prefix
const COLLECTION_PREFIX = '';

const addMinutes = (date, minutes) =>
  new Date(date.getTime() + minutes * 60000);

(async () => {
  const collectionExpiresInMinutes = {
    accesstoken: 60,
    contexttoken: 24 * 60,
    idtoken: 24 * 60,
    nonce: 2,
    state: 10,
  };

  for (const [collection, expiresInMinutes] of Object.entries(
    collectionExpiresInMinutes,
  )) {
    const documents = await db
      .collection(`${COLLECTION_PREFIX}${collection}`)
      .get();

    for (const document of documents.docs) {
      if (!document.data().createdAt) continue;
      await document.ref.update({
        expiresAt: addMinutes(
          document.data().createdAt.toDate(),
          expiresInMinutes,
        ),
      });
    }
  }

  console.log('Done');
})();

@examind/ltijs-firestore v1.1.0 - v1.3.2

@examind/litjs-firestore@1.1.0 - 1.3.2 sets the following fields on all new documents created in Firestore:

• age2MinutesAt
• age10MinutesAt
• age1HourAt
• age24HoursAt

Use these fields to set up Firestore TTL Policies to auto-purge stale documents. You only need to set this up once.

Using gcloud, substitute your project ID for {project_id} and execute the following commands. Warning, this will take a while.

gcloud firestore fields ttls update age1HourAt --collection-group=accesstoken --enable-ttl --project={project_id}
gcloud firestore fields ttls update age24HoursAt --collection-group=contexttoken --enable-ttl --project={project_id}
gcloud firestore fields ttls update age24HoursAt --collection-group=idtoken --enable-ttl --project={project_id}
gcloud firestore fields ttls update age2MinutesAt --collection-group=nonce --enable-ttl --project={project_id}
gcloud firestore fields ttls update age10MinutesAt --collection-group=state --enable-ttl --project={project_id}

To ensure that everything worked correctly, you can list all your TTL policies:

gcloud firestore fields ttls list --project={project_id}

@examind/ltijs-firestore <= v1.0.0

Use @examind/ltijs-firestore-scheduler.

Development

Clone this repo, navigate to its location in Terminal and run:

npm ci
npm run compile
npm link

In another project, link directly to this repo:

npm link @examind/ltijs-firestore

Unit Test

Running unit tests requires that the Firebase CLI (firebase-tools) is installed globally:

npm install -g firebase-tools@12.4.2
npm ci
npm run compile
npm test

To use VS Code's debugger:

• Open VS Code's JavaScript Debug Terminal
• Add breakpoints in 0-provider.js or Firestore.ts
• Then npm test inside JavaScript Debug Terminal

Publish

• Bump version in package.json
• npm install
• Commit with message: Release {version, e.g. 0.1.6}