Upload a binary image file to AWS S3 in Realm function

[Laekipia (Natacha C)]

I’m trying to implement an app similar to the O’FISH app. My images are temporarily stored as binary data in MongoDB before being sent to S3 via a Realm trigger function.

I’ve written a realm function that uploads a file to my S3 bucket. This function works fine if the file is "hello world". However, I get Error: Unsupported body payload object when my file is a binary image queried from a MongoDB document.

Here is my Realm function:

exports = function(){
  var drawings = context.services.get("Cluster0").db("databaseName").collection("drawings");

  // get drawing document
  const query = { "_id": BSON.ObjectId("61c348229f2368fd6f2a2f95")};
  const projection = {
    "_id":1,
    "thumbnail" : 1,
  }
  drawings.findOne(query, projection)
  .then(doc => {
    const imageName = doc._id.toString()
    // THE UPLOAD TO S3 WORKS WITH LINE BELOW
    // const file = 'hello world'
    const file = doc.thumbnail
    console.log('file type', Object.prototype.toString.call(file)) // this logs: [object Binary]
   
    // call uploadImageToS3 function
    context.functions.execute("uploadImageToS3", imageName, file)
    .then (() => {
      console.log('Uploaded to S3');
    })
};

And here is my uploadImageToS3 function:

exports = async function(imageName, file) {
  
  const AWS = require('aws-sdk');

  AWS.config.update({
    accessKeyId :context.values.get("AWS_ACCESS_KEY_ID"),
    secretAccessKey : context.values.get("AWS_ACCESS_KEY_SECRET"),
    region: context.values.get("AWS_REGION")
  });
  
  const s3 = new AWS.S3({apiVersion: '2006-03-01'})
  const bucketName = context.values.get("AWS_BUCKET")
  
  return s3.upload({
        "Bucket": bucketName,
        "Key" : imageName,
        "Body": file,
        "ACL": "public-read",
        "ContentType": "image/jpeg",
        }).promise()
}

How do I upload a binary image (straight out of a MongoDB document) to S3?

Many thanks in advance!