Using AWS Lambda and povray to render images

povray_lambda.js

var async = require('async');
var AWS = require('aws-sdk');
var util = require('util');
var spawn = require('child_process').spawn;
var fs = require('fs');

var s3 = new AWS.S3();

// globals
var dstBucket = "outrender1121"


exports.handler = function(event, context) {
	console.log("Reading options from event:\n", util.inspect(event, {depth: 5}));
	var srcBucket = event.Records[0].s3.bucket.name;
	var srcKey    = event.Records[0].s3.object.key;
	var dstKey    = "out_" + srcKey + ".png";

	// Sanity checks
	if (srcBucket == dstBucket) {
		console.error("Destination bucket must not match source bucket.", srcBucket, dstBucket);
		return;
	}

	var typeMatch = srcKey.match(/\.([^.]*)$/);
	if (!typeMatch) {
		console.log('skipping non-povfile: ' + srcKey);
		return;
	}
	
	var imageType = typeMatch[1];
	if (imageType != "pov") {
		console.log('skipping non-povfile: ' + srcKey);
		return;
	}

	// Download the image from S3, transform, and upload to a different S3 bucket.
	async.waterfall([
	    
	    //
	    // Get from S3
	    //
		function download(next) {
			// Download the image from S3 into a buffer.
			s3.getObject({
					Bucket: srcBucket,
					Key: srcKey
				},
				next);
            console.log("GET "+srcKey);
			},

        //
        // Write to a file for povray -- must be in /tmp/
        //
		function write_to_file(response, next) {
            fs.writeFile("/tmp/stdin.pov", response.Body, next);
        },  

	    //
	    // Render
	    //
		function transform(next) {
            var convert = spawn('./povray_37_aws', ['/tmp/stdin.pov', '-w300', '-h300', '-O-']);

            var buffers = [];
            convert.stdout.on('data', function(data) {
              buffers.push(new Buffer(data, "binary"));
            });

            convert.stderr.on('data', function(data) {
                // otherwise it hangs waiting to be read
            });
            
            convert.on('exit', function(code) {
             console.log("exit");
             var allbuffer = Buffer.concat(buffers)
             next(null, "content-type:image/PNG", allbuffer);
            });
		},

	    //
	    // Put back on S3
	    //
		function upload(contentType, data, next) {
			// Stream the transformed image to a different S3 bucket.
			s3.putObject({
					Bucket: dstBucket,
					Key: dstKey,
					Body: data,
					ContentType: contentType
				},
				next);
			}
		], function (err) {
			if (err) {
				console.error(
					'Failed: ' + srcBucket + '/' + srcKey + ' ' + dstBucket + '/' + dstKey +
					' Error: ' + err
				);
			} else {
				console.log(
					'Succeeded: ' + srcBucket + '/' + srcKey + ' ' + dstBucket + '/' + dstKey
				);
			}

			context.done();
		}
	);
};