Node resize image and upload to AWS - node.js

Question

I'm relatively new to node, and want to write a module that takes an image from an S3 bucket, resizes it and saves it to a temporary directory on Amazon's new Lambda service and then uploads the images back to the bucket.
When I run the code, none of my functions seem to be called (download, transform and upload). I am using tmp to create the temporary directory and graphicsMagick to resize the image.
What is wrong with my code?
I have defined the dependencies and the array outside of the module, because I have another which depends on these.
// dependencies
var AWS = require('aws-sdk');
var gm = require('gm').subClass({ imageMagick: true });
var fs = require("fs");
var tmp = require("tmp");
// get reference to S3 client
var s3 = new AWS.S3();
var _800px = {
width: 800,
destinationPath: "large"
};
var _500px = {
width: 500,
destinationPath: "medium"
};
var _200px = {
width: 200,
destinationPath: "small"
};
var _45px = {
width: 45,
destinationPath: "thumbnail"
};
var _sizesArray = [_800px, _500px, _200px, _45px];
var len = _sizesArray.length;
exports.AwsHandler = function(event) {
// Read options from the event.
var srcBucket = event.Records[0].s3.bucket.name;
var srcKey = event.Records[0].s3.object.key;
var dstnKey = srcKey;
// create temporary directory
var tmpobj = tmp.dirSync();
// function to determine paths
function _filePath (directory, i) {
if (!directory) {
return "dst/" + _sizesArray[i].destinationPath + "/" + dstnKey;
} else {
return directory + "/dst/" + _sizesArray[i].destinationPath + "/" + dstnKey;
}
};
// Infer the image type.
var typeMatch = srcKey.match(/\.([^.]*)$/);
if (!typeMatch) {
console.error('unable to infer image type for key ' + srcKey);
return;
};
var imageType = typeMatch[1];
if (imageType != "jpg" && imageType != "png") {
console.log('skipping non-image ' + srcKey);
return;
};
(function resizeImage () {
function download () {
console.log("started!");
s3.getObject({
Bucket: srcBucket,
Key: srcKey
},
function (err, response) {
if (err) {
console.error(err);
}
// call transform if successful
transform (response);
}
);
};
function transform (response) {
for ( var i = 0; i<len; i++ ) {
// define path for image write
var _Key = _filePath (tmpobj, i);
// resize images
gm(response.Body, srcKey)
.resize(_sizesArray[i].width)
.write(_Key, function (err) {
if (err) {
console.error(err);
}
upLoad ();
});
}
};
function upLoad () {
for ( var i = 0; i<len; i++ ) {
var readPath = _filePath (tmpobj, i);
var writePath = _filePath (i);
// read file from temp directory
fs.readFile(readPath, function (err, data) {
if (err) {
console.error(err);
}
// upload images to s3 bucket
s3.putObject({
Bucket: srcBucket,
Key: writePath,
Body: data,
ContentType: data.type
},
function (err) {
if (err) {
console.error(err);
}
console.log("Uploaded with success!");
});
})
}
// Manual cleanup of temporary directory
tmpobj.removeCallback();
};
}());
};

Answer 1

Here's a partial improvement, note the use of the async library. You will have issues in upLoad() because you are firing four asynchronous calls immediately (in the for loop) and there's no easy way to know when they are all done. (well, the easy way is to rewrite the function to use the async library, like async.forEach)
// dependencies
var AWS = require('aws-sdk');
var gm = require('gm').subClass({ imageMagick: true });
var fs = require("fs");
var tmp = require("tmp");
var async = require("async");
// get reference to S3 client
var s3 = new AWS.S3();
var _800px = {
width: 800,
destinationPath: "large"
};
var _500px = {
width: 500,
destinationPath: "medium"
};
var _200px = {
width: 200,
destinationPath: "small"
};
var _45px = {
width: 45,
destinationPath: "thumbnail"
};
var _sizesArray = [_800px, _500px, _200px, _45px];
var len = _sizesArray.length;
exports.AwsHandler = function(event) {
// Read options from the event.
var srcBucket = event.Records[0].s3.bucket.name;
var srcKey = event.Records[0].s3.object.key;
var dstnKey = srcKey;
// create temporary directory
var tmpobj = tmp.dirSync();
// function to determine paths
function _filePath (directory, i) {
if (!directory) {
return "dst/" + _sizesArray[i].destinationPath + "/" + dstnKey;
} else {
return directory + "/dst/" + _sizesArray[i].destinationPath + "/" + dstnKey;
}
};
// Infer the image type.
var typeMatch = srcKey.match(/\.([^.]*)$/);
if (!typeMatch) {
console.error('unable to infer image type for key ' + srcKey);
return;
};
var imageType = typeMatch[1];
if (imageType != "jpg" && imageType != "png") {
console.log('skipping non-image ' + srcKey);
return;
};
// Actually call resizeImage, the main pipeline function:
resizeImage(function(err){
// Done. Manual cleanup of temporary directory
tmpobj.removeCallback();
})
function resizeImage (callback) {
var s3obj = {
Bucket: srcBucket,
Key: srcKey
};
download(s3obj, function(response){
var gmConfigs = sizesArray.map(function(size, i){
return {
width: size.width
_Key: _filePath (tmpobj, i)
}
})
async.eachSeries(gmConfigs,
function(config, done){
transform(response, config.width, config._Key, done)
},
function(err){
if(err){
console.log(err);
} else {
upLoad();
// Further work is required to identify if all the uploads worked,
// and to know when to call callback() here
// callback();
}
})
})
}
function download (s3obj, callback) {
console.log("started!");
s3.getObject(s3obj, function (err, response) {
if (err) {
console.error(err);
}
// call transform if successful
callback(response);
});
};
function transform (response, width, _Key, callback) {
// resize images
gm(response.Body, srcKey)
.resize(width)
.write(_Key, function (err) {
if (err) {
console.error(err);
}
callback();
});
};
function upLoad () {
for ( var i = 0; i<len; i++ ) {
var readPath = _filePath (tmpobj, i);
var writePath = _filePath (i);
// read file from temp directory
fs.readFile(readPath, function (err, data) {
if (err) {
console.error(err);
}
// upload images to s3 bucket
s3.putObject({
Bucket: srcBucket,
Key: writePath,
Body: data,
ContentType: data.type
},
function (err) {
if (err) {
console.error(err);
}
console.log("Uploaded with success!");
});
})
}
};
};