Connecting to a Non-Default Firestore Database from Cloud Run Functions (Node.js)

Normally, when connecting to Google Cloud Firestore, the default database is used. However, in cases where you want to handle multiple databases, you will need to access a non-default database.

This article documents the steps to connect to a non-default Firestore database from a Cloud Run function. In short, it only requires specifying the database name from the SDK. The conclusive code is provided below.

import { Firestore } from "@google-cloud/firestore";

const db = new Firestore({
  databaseId: "rss-manager",
});

With this, the db instance will be pointed to the rss-manager database instead of the default one.

Background of the struggle: Google Cloud SDK vs. Firebase Admin SDK

The solution is quite simple, but it took some time to get there. To use Firestore from a Node.js Cloud Run function, using an SDK is easy. The problem is that there are two main types of SDKs.

Package Name	Type of SDK	Overview
firebase-admin	Firebase Admin SDK	Library for Firebase server-side applications
@google-cloud/firestore	Google Cloud SDK	General Google Cloud library

Since both Cloud Run functions and Firestore can be used with Firebase, a Google search often yields methods using firebase-admin. However, I couldn't figure out how to access a non-default database with firebase-admin.

@google-cloud/firestore is an alternative method, and for me, who doesn't usually use Firebase, this approach was easier and helpful.

Registering RSS feed URLs from a Cloud Run function

Since we're at it, let's go through a sample implementation. We will implement an API that can register RSS feed URLs to Firestore from a Cloud Run function.

Create a Firestore database

Create a database named rss-manager.

Cloud Run function

I will implement it in TypeScript and then convert it to Node.js. Import Firestore from '@google-cloud/firestore'; and create a DB client with new Firestore(). At this time, by specifying databaseId: 'rss-manager' as an option, you can access the database created earlier.

index.ts

import type { Request, Response } from 'express';
import { Firestore } from '@google-cloud/firestore';

const db = new Firestore({
  databaseId: 'rss-manager',
});

// Firestore collection name
const COLLECTION_NAME = 'rss-feeds';

// HTTP function to register RSS feed URLs in Firestore
export const rssRegister = async (req: Request, res: Response) => {
  const rssUrl = req.body.url;

  if (!rssUrl) {
    res.status(400).send('RSS URL is required.');
    return;
  }

  try {
    // Save RSS URL to Firestore
    await db.collection(COLLECTION_NAME).add({
      url: rssUrl,
      lastCheckedGuid: null, // Set to null initially to detect all new articles
    });
    res.status(200).send(`RSS URL added: ${rssUrl}`);
  } catch (error) {
    console.error('Error adding RSS URL:', error);
    res.status(500).send('Failed to add RSS URL.');
  }

Let's deploy it. Note that this assumes the default service account has access to Firestore.

gcloud functions deploy rssRegister \
--region=asia-northeast1 \
--runtime=nodejs20 \
--memory=256 \
--timeout=30s \
--source=. \
--trigger-http \
--project=my-project-name \
--entry-point=rssRegister \
--allow-unauthenticated

Let's try registering a URL from the test tab of the deployed Cloud Run function.

Confirm that it has been registered in Firestore.

We were able to register data into a non-default Firestore database from a Cloud Run function.

Conclusion

We registered an RSS feed URL to a non-default Firestore database from a Cloud Run function using @google-cloud/firestore. I hope this was helpful. If anyone knows how to access a non-default database with firebase-admin, please let me know.

References

https://github.com/googleapis/nodejs-firestore/blob/main/types/firestore.d.ts#L387-L400

Ultimately, I couldn't find any specific documentation and discovered databaseId from the @google-cloud/firestore GitHub type definitions.

Source

https://github.com/cm-wada-yusuke/llm-reviewer/tree/main/rss-manager