Serve cached images from s3 instead of cloudinary. It needs tidying but it works and reduces bandwidth dramatically. - inspired by https://gist.github.com/dboskovic/23858511bf3c1cbebdbd

ExampleModel.js

//... 
Model.add({
	content: { 
		type: Types.Html, wysiwyg: true, height: 400
	},

	hash : {
		type : String,
		hidden : true
	},
	
	cachedContent : {
		type : Types.Html,
		hidden : true
	},
});

middleware.js

var jsdom = require('jsdom');
var crypto = require('crypto');
var request = require('request');
var path = require('path');
var fs = require('fs');
var s3 = require('s3');
var imageCache = keystone.list('ImageCache').model;
var tempDir = path.join(process.cwd(), 'temp/');
var s3Bucket = 'YOUR_BUCKET';

if (!fs.existsSync(tempDir)) {
	fs.mkdirSync(tempDir);
}
//...
/**
 * Parse the content and cache wysiwyg content
 */
locals.renderCachedContent = function(content, contentField){
	if(content.cachedContent && content.hash === crypto.createHash('md5').update(content[contentField]).digest('hex')) {
		console.log('content cached');
		return content.cachedContent;
	}

	console.log('not cached', content.hash);

	var _content = '';

	jsdom.env(
		content[contentField],
		["http://code.jquery.com/jquery.js"],
		function (errors, window) {
			total = window.$("img").length;
			var _content = content[contentField];

			// loop all images
			window.$.each(window.$("img"), function(i, v){

				// not a cloudinary image
				if(!/cloudinary/.test(v.src)) {
					console.log('not cloudinary');
					return false;
				}
				
				function saveImage($img) {
					var fileName = hash + '.jpg';
					request(v.src)
						.pipe(fs.createWriteStream(tempDir + fileName))
						.on('close', function (error, response, body) {
							var params = {
								localFile: tempDir + fileName,
								s3Params: {
									Bucket: s3Bucket,
									Key: 'c/' + fileName,
									ACL:'public-read',
									ContentType:'image/jpeg'
								},
							};

							var uploader = s3Client.uploadFile(params);
							uploader.on('error', function(err) {
								console.log('error caching image', err)
								$img.remove()
							})
							.on('end', function() {
								if(!$img) {
									console.log('unknown issue');
									return;
								}
								
								console.log('successful image upload', v.src)
								$img.uploaded = true;
								$img.save()
								console.log($img);
							});
						});
				}
				
				var hash = crypto.createHash('md5').update(v.src).digest('hex');
				imageCache.where({hash:hash})
					.findOne(function(err,data){
						// no cache found
						if(!data){
							imageCache.create({ hash:hash, uploaded: false},function(err, $img){
								saveImage(data);
							});
						}

						if(data && !data.uploaded) {
							saveImage(data);
						}
						console.log('uploaded to s3');
						_content = _content.replace(v.src, 'http://' + s3Bucket + '.s3.amazonaws.com/c/' + hash + '.jpg');


						content.cachedContent = _content;
						content.hash = crypto.createHash('md5').update(content[contentField]).digest('hex');
						content.save();
					});
			}); //end each
			console.log(content.hash, crypto.createHash('md5').update(content[contentField]).digest('hex'));
		}
	);

	return content.content;
};

view.jade

div!= renderCachedContent(model, 'content')