Backblaze B2 Event Notifications Demo: Thumbnail Creator in Node.js

This app receives a Backblaze Event Notification message, validates the message signature, and, if the message concerns a newly-created image file, creates a thumbnail image and uploads it to the same bucket as the image file.

Prerequisites

Follow these instructions, as necessary, to create a Backblaze B2 account, bucket and application key:

• Create a Backblaze B2 Account.
• Create a Backblaze B2 Bucket.
• Create an Application Key with access to the bucket you wish to use.

Be sure to copy the application key as soon as you create it, as you will not be able to retrieve it later!

Configuration

Copy .env.template to .env, then paste in your application key, endpoint, etc.:

AWS_ACCESS_KEY_ID=<Your Backblaze B2 Application Key ID>
AWS_SECRET_ACCESS_KEY=<Your Backblaze B2 Application Key>
AWS_ENDPOINT_URL=https://<Your Backblaze B2 bucket endpoint>
AWS_REGION=<Your Backblaze B2 bucket region>
RESIZE_OPTIONS={"width": 240, "withoutEnlargement": true}
SIGNING_SECRET=<Your Event Notification rule signing secret>
NODE_ENV=development

Running the App Locally

Install dependencies:

npm install

Start the app:

npm start

By default, the app will verify that it can access Backblaze B2, then start listening for requests on port 3000:

> [email protected] start
> node app.js

Successfully called S3 service at https://s3.us-west-004.backblazeb2.com/: 61 buckets listed
Listening on port 3000

You can set the PORT environment variable to override the default, e.g.:

% PORT=80 npm start

> [email protected] start
> node app.js

Successfully called S3 service at https://s3.us-west-004.backblazeb2.com/: 61 buckets listed
Listening on port 80

You can use ngrok or TryCloudflare to create an Internet-addressable endpoint to test the app with Event Notifications:

ngrok http http://localhost:3000

or

cloudflared tunnel --url http://localhost:3000

Make a note of the resulting URL. You will use this as the target URL when you create an Event Notification rule.

Running the App on Docker

Building a Docker Image

You will need to build a Docker image. Note that Docker defaults to building an image for the platform on which it is running, so, if you are working on a Mac with an Apple CPU and you will be deploying to a Linux VM running on Intel, you must specify the --platform flag. For example:

docker build --platform linux/amd64 .

You can then tag and push the image to the repository of your choice. Alternatively, you can combine building, tagging and pushing into a single command:

docker build --push --platform linux/amd64 --tag docker_user/b2-node-thumbnail-demo:1.0.0 .

If you are using containerd for pulling and storing images, you can build a multi-platform image:

docker build \
--push \
--platform linux/arm/v7,linux/arm64/v8,linux/amd64 \
--tag docker_user/b2-node-thumbnail-demo:1.0.0 .

Running the App in a New Local Docker Container

When running the app, you must:

• Use the -p flag to bind port 3000 of the container to an available port on the host.
• Specify values for the environment variables listed in .env.template, via multiple uses of the -e/--env flag or by using the --env-file flag to load the environment variables from a file.

For example, to use port 80 on the host and load environment variables from the .env file, you would run:

docker run -p 80:3000 --env-file .env docker_user/b2-node-thumbnail-demo:1.0.0

Again, you can use ngrok or TryCloudflare to create an Internet-addressable endpoint, noting the URL to use as the target URL in your Event Notification rule:

ngrok http http://localhost:3000

or

cloudflared tunnel --url http://localhost:3000

Running the App on a Cloud Compute Provider

You should be able to run the app on any cloud compute provider. Note that you must configure the port and environment variables similarly to running the app locally, and make a note of your app's public URL.

Check the application log for the Successfully called S3 service message. If you do not see this, then look for an error message, and check the app configuration.

Creating an Event Notification Rule

Follow this tutorial to create an Event Notification rule, using the URL that you noted earlier rather than the Webhook.site endpoint.

Verifying that the App Creates Thumbnails

Use the Backblaze B2 web UI to upload an image file to your bucket. Wait a few seconds, then refresh the bucket listing. You should see the thumbnail file in the bucket.

If you do not see the thumbnail file, check the application log.