Thumbd

Build Status:

Thumbd is an image thumbnailing server built on top of Node.js, SQS, S3, and ImageMagick.

You can easily run Thumbd on Heroku. Simply set the appropriate environment variables with config:set and deploy using the Procfile provided.

Setup

apt-get install imagemagick
npm install thumbd

Thumbd requires the following environment variables to be set:

• AWS_KEY the key for your AWS account (the IAM user must have access to the appropriate SQS and S3 resources).
• AWS_SECRET the AWS secret key.
• BUCKET the bucket to download the original images from. The thumbnails will also be placed in this bucket.
• CONVERT_COMMAND the ImageMagick convert command. Defaults to convert.
• REQUEST_TIMEOUT how long to wait in milliseconds before aborting a remote request. Defaults to 15000.
• S3_ACL the acl to set on the uploaded images. Must be one of private, or public-read. Defaults to private.
• S3_STORAGE_CLASS the storage class for the uploaded images. Must be either STANDARD or REDUCED_REDUNDANCY. Defaults to STANDARD.
• SQS_QUEUE the queue name to listen for image thumbnailing.
  • As of version 2.0.0, the integer identifier from the queue URL is no longer required.

You can export these variables to your environment, or specify them when running the thumbd CLI.

Personally, I set these environment variables in a .env file and execute thumbd using Foreman.

Server

The thumbd server:

• listens for thumbnailing jobs on the queue specified.
• downloads the original image from our thumbnailng S3 bucket, or from an HTTP(s) resource.
  • HTTP resources are prefixed with http:// or https://.
  • S3 resources are a path to the image in the S3 bucket indicated by the BUCKET environment variable.
• Uses ImageMagick to perform a set of transformations on the image.
• uploads the thumbnails created back to S3, with the following naming convention: [original filename excluding extension]_[thumbnail suffix].jpg

Assume that the following thumbnail job was received over SQS:

{
	"original": "example.png",
	"descriptions": [
		{
			"suffix": "tiny",
			"width": 48,
			"height": 48
		},
		{
			"suffix": "small",
			"width": 100,
			"height": 100,
			"background": "red"
		},
		{
			"suffix": "medium",
			"width": 150,
			"height": 150,
			"strategy": "bounded"
		}
	]
}

Once thumbd processes the job, the files stored in S3 will look something like this:

• /example.png
• /example_tiny.jpg
• /example_small.jpg
• /example_medium.jpg

Client

Submit thumbnailing jobs from your application by creating an instance of a thumbd client (clients will soon be offered for other languages).

var Client = require('./thumbd').Client,
	client = new Client({
		awsKey: 'AWS-KEY',
		awsSecret: 'AWS-SECRET',
		sqsQueue: 'thumbnailing-queue',
		s3Bucket: 'thumbnails'
	});

var destination = '/example/awesome.jpg';

client.upload('/tmp/awesome.jpg', destination, function(err) {
	if (err) throw err;
	client.thumbnail(destination, [{suffix: 'small', width: 100, height: 100, background: 'red', strategy: 'matted'}]);
});

Thumbnail Descriptions

The descriptions received in the thumbnail job describe the way in which thumbnails should be generated.

description accepts the following keys:

• suffix a suffix describing the thumbnail.
• width the width of the thumbnail.
• height the height of the thumbnail.
• background background color for matte.
• format what should the output format of the image be, e.g., jpg, gif, defaults to jpg.
• strategy indicate an approach for creating the thumbnail.
  • matted maintain aspect ratio, places image on width x height matte.
  • bounded (default) maintain aspect ratio, don't place image on matte.
  • fill both resizes and zooms into an image, filling the specified dimensions.
• quality the quality of the thumbnail, in percent. e.g. 90.

CLI

Starting the server:

thumbd server --aws_key=<key> --aws_secret=<secret> --tmp_dir=</tmp> --sqs_queue=<sqs queue name> --bucket=<s3 thumbnail bucket> --s3_acl=<private or public-read> --s3_storage_class=<STANDARD or REDUCED_REDUNDANCY>

Manually submitting an SQS thumbnailing job (useful for testing purposes):

thumbd thumbnail --remote_image=<path to image s3 or http> --descriptions=<path to thumbnail description JSON file> --aws_key=<key> --aws_secret=<secret> --sqs_queue=<sqs queue name>

• remote_image indicates the S3 object to perform the thumbnailing operations on.
• thumbnail_descriptions the path to a JSON file describing the dimensions of the thumbnails that should be created (see example.json in the data directory).

Production Notes

At Attachments.me, thumbd thumbnails tens of thousands of images a day. There are a few things you should know about our production deployment:

• thumbd was not designed to be bullet-proof:
  • it is run with an Upstart script, which keeps the thumbnailing process on its feet.
• Node.js is a single process, this does not take advantage of multi-processor environments.
  • we run an instance of thumbd per-CPU on our servers.
• we use Foreman's export functionality to simplify the process of creating Upstart scripts.
• be midful of the version of ImageMagick you are running:
  • make sure that you build it with the appropriate extensions for images you would like to support.
  • we've had issues with some versions of ImageMagick, we run 6.6.2-6 in production.
• Your SQS settings are important:
  • setup a visibility-timeout/message-retention value that allows for a reasonable number of thumbnailing attempts.
  • we use long-polling to reduce the latency time before a message is read.
• in production, thumbd runs on Node 0.8.x. It has not been thoroughly tested with Streams 2.

The Future

thumbd is a rough first pass at creating an efficient, easy to deploy, thumbnailing pipeline. Please be liberal with your feature-requests, patches, and feedback.

Copyright

Copyright (c) 2012 Attachments.me. See LICENSE.txt for further details.