Download image from S3 bucket to Lambda temp folder (Node.js)

Question

Good day guys.

I have a simple question: How do I download an image from a S3 bucket to Lambda function temp folder for processing? Basically, I need to attach it to an email (this I can do when testing locally).

I have tried:

s3.download_file(bucket, key, '/tmp/image.png')

as well as (not sure which parameters will help me get the job done):

s3.getObject(params, (err, data) => {
    if (err) {
        console.log(err);
        const message = `Error getting object ${key} from bucket ${bucket}.`;
        console.log(message);
        callback(message);
    } else {

        console.log('CONTENT TYPE:', data.ContentType);
        callback(null, data.ContentType);
    }
});

Like I said, simple question, which for some reason I can't find a solution for.

Thanks!

Answer 1

If you're writing it straight to the filesystem you can also do it with streams. It may be a little faster/more memory friendly, especially in a memory-constrained environment like Lambda.

var fs = require('fs');
var path = require('path');

var params = {
    Bucket: "mybucket",
    Key: "image.png"
};

var tempFileName = path.join('/tmp', 'downloadedimage.png');
var tempFile = fs.createWriteStream(tempFileName);

s3.getObject(params).createReadStream().pipe(tempFile);