I know there's been a lot of coverage on upload to AWS S3. However, I've been struggling with this for about 24 hours now and I have not found any answer that fits my situation.
Upload a file to AWS S3 directly from my client to my S3 bucket. The situation is:
FormData
and Angular's $http
). It consisted of getting a signed URL from AWS on the server (and that part worked), then AJAX-uploading to that URL. It failed with some mysterious CORS-related message (although I did set a CORS config on Heroku)It seems I'm facing 2 difficulties: having a file input that works in my Single Page App, and getting AWS's workflow right.
If possible, I'd like to avoid 'all included' solutions that manage the whole process while hiding of all of the complexity, making it hard to adapt to special cases. I'd much rather have a simple explanation breaking down the flow of data between the various components involved, even if it requires some more plumbing from me.
I finally managed. The key points were:
$http
, and use native XMLHttpRequest
instead.getSignedUrl
feature of AWS's SDK, instead on implementing my own signature-generating workflow like many libraries do.'eu-central-1'
in the case of Frankfurt).Here below is a step-by-step guide of what I did; it uses AngularJS and NodeJS on the server, but should be rather easy to adapt to other stacks, especially because it deals with the most pathological cases (SPA on a different domain that the server, with a bucket in a recent - at the time of writing - region).
Make sure that:
All that matters is to have a workflow that eventually gives you programmatic access to a File
object - without uploading it.
In my case, I used the ng-file-select
and ng-file-drop
directives of the excellent angular-file-upload library. But there are other ways of doing it (see this post for example.).
Note that you can access useful information in your file object such as file.name
, file.type
etc.
On your server, you can use the AWS SDK to obtain a secure, temporary URL to PUT
your file from someplace else (like your frontend).
In NodeJS, I did it this way:
// ---------------------------------
// some initial configuration
var aws = require('aws-sdk');
aws.config.update({
accessKeyId: process.env.AWS_ACCESS_KEY,
secretAccessKey: process.env.AWS_SECRET_KEY,
signatureVersion: 'v4',
region: 'eu-central-1'
});
// ---------------------------------
// now say you want fetch a URL for an object named `objectName`
var s3 = new aws.S3();
var s3_params = {
Bucket: MY_BUCKET_NAME,
Key: objectName,
Expires: 60,
ACL: 'public-read'
};
s3.getSignedUrl('putObject', s3_params, function (err, signedUrl) {
// send signedUrl back to client
// [...]
});
You'll probably want to know the URL to GET your object to (typically if it's an image). To do this, I simply removed the query string from the URL:
var url = require('url');
// ...
var parsedUrl = url.parse(signedUrl);
parsedUrl.search = null;
var objectUrl = url.format(parsedUrl);
Now that your client has your File
object and the signed URL, it can send the PUT request to S3. My advice in Angular's case is to just use XMLHttpRequest instead of the $http
service:
var signedUrl, file;
// ...
var d_completed = $q.defer(); // since I'm working with Angular, I use $q for asynchronous control flow, but it's not mandatory
var xhr = new XMLHttpRequest();
xhr.file = file; // not necessary if you create scopes like this
xhr.onreadystatechange = function(e) {
if ( 4 == this.readyState ) {
// done uploading! HURRAY!
d_completed.resolve(true);
}
};
xhr.open('PUT', signedUrl, true);
xhr.setRequestHeader("Content-Type","application/octet-stream");
xhr.send(file);
I would like to thank emil10001 and Will Webberley, whose publications were very valuable to me for this issue.
You can use the ng-file-upload $upload.http method in conjunction with the aws-sdk getSignedUrl to accomplish this. After you get the signedUrl back from your server, this is the client code:
var fileReader = new FileReader();
fileReader.readAsArrayBuffer(file);
fileReader.onload = function(e) {
$upload.http({
method: 'PUT',
headers: {'Content-Type': file.type != '' ? file.type : 'application/octet-stream'},
url: signedUrl,
data: e.target.result
}).progress(function (evt) {
var progressPercentage = parseInt(100.0 * evt.loaded / evt.total);
console.log('progress: ' + progressPercentage + '% ' + file.name);
}).success(function (data, status, headers, config) {
console.log('file ' + file.name + 'uploaded. Response: ' + data);
});
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With