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

You can get the image using the aws s3 api, then write it to the tmp folder using fs.
var params = { Bucket: "BUCKET_NAME", Key: "OBJECT_KEY" };
s3.getObject(params, function(err, data){ if (err) {
console.error(err.code, "-", err.message);
return callback(err); }
fs.writeFile('/tmp/filename', data.Body, function(err){
if(err)
console.log(err.code, "-", err.message);
return callback(err);
});
});
Out of curiousity, why do you need to write the file in order to attach it? It seems kind of redundant to write the file to disk so that you can then read it from disk

Answer 2

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);

Answer 3

// Using NodeJS version 10.0 or later and promises
const fsPromise = require('fs').promises;
try {
const params = {
Bucket: 's3Bucket',
Key: 'file.txt',
};
const data = await s3.getObject(params).promise();
await fsPromise.writeFile('/tmp/file.txt', data.Body);
} catch(err) {
console.log(err);
}

Answer 4

I was having the same problem, and the issue was that I was using Runtime.NODEJS_12_X in my AWS lambda.
When I switched over to NODEJS_14_X it started working for me :').
Also
The /tmp is required. It will directly write to /tmp/file.ext.