I have my own REST API to call in order to download a file. (At the end, the file could be store in different kind of server... Amazon s3, locally etc...)

To get a file from s3, I should use this method:

var url = s3.getSignedUrl('getObject', params);

This will give me a downloadable link to call.

Now, my question is, how can I use my own rest API to download a file when it es from that link? Is there a way to redirect the call?

I'm using Hapi for my REST server.

{
    method: "GET", path: "/downloadFile",
    config: {auth: false},
    handler: function (request, reply) {
        // TODO
        reply({})
    }
},

I have my own REST API to call in order to download a file. (At the end, the file could be store in different kind of server... Amazon s3, locally etc...)

To get a file from s3, I should use this method:

var url = s3.getSignedUrl('getObject', params);

This will give me a downloadable link to call.

Now, my question is, how can I use my own rest API to download a file when it es from that link? Is there a way to redirect the call?

I'm using Hapi for my REST server.

{
    method: "GET", path: "/downloadFile",
    config: {auth: false},
    handler: function (request, reply) {
        // TODO
        reply({})
    }
},

• javascript
• rest
• amazon-web-services
• amazon-s3
• hapi.js

• Why do you need the link to then call that link to download the file, why not just download the file and return the stream? – peteb Commented Feb 1, 2017 at 16:34
• @peteb Wouldn't that make the file be downloaded 2 times for one request? Client will have to wait until the file is downloaded from the server, then stream to him? – Jaythaking Commented Feb 1, 2017 at 16:40
• not if you return the stream back to the requester. Think about it like this, you can get a stream from S3 with the contents of that file, you can then use pipe() to pipe the S3 stream directly back to the requester. It is never downloaded to the mediator, instead the mediator is just a go between. Especially if you use the AWS-SDK unbufferedStream. – peteb Commented Feb 1, 2017 at 16:42
• How do I setup the Hapi request for that? Do you have an example for me of a pipe request? Thx – Jaythaking Commented Feb 1, 2017 at 16:47
• I don't find any method call for an unbuffered stream in s3 javascript – Jaythaking Commented Feb 1, 2017 at 16:52

2 Answers 2

Instead of using a redirect to download the desired file, just return back an unbufferedStream instead from S3. An unbufferedStream can be returned from the HttpResponse within the AWS-SDK. This means there is no need to download the file from S3, then read it in, and then have the requester download the file.

FYI I use this getObject() approach with Express and have never used Hapi, however I think that I'm pretty close with the route definition but hopefully it will capture the essence of what I'm trying to achieve.

Hapi.js route

const getObject = require('./getObject');

{
    method: "GET", path: "/downloadFile",
    config: {auth: false},
    handler: function (request, reply) {
        let key = ''; // get key from request
        let bucket = ''; // get bucket from request

        return getObject(bucket, key)
          .then((response) => {
            reply.statusCode(response.statusCode);

            response.headers.forEach((header) => {
              reply.header(header, response.headers[header]);
            });

            return reply(response.readStream);
          })
          .catch((err) => {
            // handle err
            reply.statusCode(500);
            return reply('error');
          });
    }
},

getObject.js

const AWS = require('aws-sdk');
const S3 = new AWS.S3(<your-S3-config>);

module.exports = function getObject(bucket, key) {
  return new Promise((resolve, reject) => {
    // Get the file from the bucket
    S3.getObject({
      Bucket: bucket,
      Key: key
    })
      .on('error', (err) => {            
        return reject(err);
      })
      .on('httpHeaders', (statusCode, headers, response) => {
        // If the Key was found inside Bucket, prepare a response object
        if (statusCode === 200) {
          let responseObject = {
            statusCode: statusCode,
            headers: {
              'Content-Disposition': 'attachment; filename=' + key
            }
          };

          if (headers['content-type'])
            responseObject.headers['Content-Type'] = headers['content-type'];
          if (headers['content-length'])
            responseObject.headers['Content-Length'] = headers['content-length'];

          responseObject.readStream = response.httpResponse.createUnbufferedStream();
          return resolve(responseObject);
        }
      })
      .send();
  });
}

Return a HTTP 303 Redirect with the Location header set to the blob's public URL in the S3 bucket.

If your bucket is private then you need to proxy the request instead of performing a redirect, unless your clients also have access to the bucket.