AWS Lambda get s3 object data template not working - amazon-web-services

Question

I am working on understanding Amazon Lambda. This is modified only slightly from the s3 template to view content type of uploaded file.
my received event log, and params log both show up in cloud watch however it's like the s3.getObject() never gets executed, as neither the error log of the data log ever get shown in the logs and all I get is a task timed out after timeout period.
var aws = require('aws-sdk');
var s3 = new aws.S3({apiVersion: 'latest'});
exports.handler = function(event, context) {
console.log('Received event:', JSON.stringify(event, null, 2));
// Get the object from the event and show its content type
var bucket = event.Records[0].s3.bucket.name;
var key = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, ' '));
var params = {
Bucket: bucket,
Key: key
};
console.log(params);
s3.getObject(params, function(err, data) {
if (err) console.log(err, err.stack); // an error occurred
else console.log(data); // successful response
/*
if (err) {
var message = "Error getting object " + key + " from bucket " + bucket +
". Make sure they exist and your bucket is in the same region as this function.";
console.log(message);
context.fail(message);
} else {
console.log('CONTENT TYPE:', data.ContentType);
context.succeed(data.ContentType);
}
*/
});
};
Here is the current IM role do I need to make some changes?
{
"Version": "2012-10-17",
"Statement": [{
"Effect": "Allow",
"Action": [
"logs:CreateLogGroup",
"logs:CreateLogStream",
"logs:PutLogEvents"],
"Resource": "arn:aws:logs:*:*:*"
},
{
"Effect": "Allow",
"Action": [
"ec2:CreateNetworkInterface",
"ec2:DescribeNetworkInterfaces",
"ec2:DetachNetworkInterface",
"ec2:DeleteNetworkInterface"],
"Resource": "*"
},
{
"Effect": "Allow",
"Action": [
"s3:ListAllMyBuckets",
"s3:ListBucket",
"s3:GetBucketLocation",
"s3:GetObject",
"s3:PutObject"],
"Resource": "arn:aws:s3:::*"
},
{
"Action": "lambda:*",
"Effect": "Allow",
"Resource": "arn:aws:lambda:*"
}]
}

Answer 1

I've run into this issue before. This happens after the validate, build, and sign callbacks execute, but before the send callback occurs. Essentially, one of the sockets go into Zombie mode. I've reported this to AWS, but they have not yet produced a fix. To "fix", set the socket timeout when instantiating the s3 client. The socket will timeout and the operation will automatically retry.
var s3 = new AWS.S3({httpOptions: { timeout: 2000 }});
By default, the timeout is two minutes, which is why it is problematic if this occurs in a Lambda where the timeout is significantly shorter.

Answer 2

Before ListBucket you need ListAllBuckets.
I advise you to restrict your lambda access.
{
"Statement":[
{
"Effect":"Allow",
"Action":[
"s3:ListAllMyBuckets"
],
"Resource":"arn:aws:s3:::*"
},
{
"Effect":"Allow",
"Action":[
"s3:ListBucket",
"s3:GetBucketLocation"
],
"Resource":"arn:aws:s3:::yourBucket"
},
{
"Effect":"Allow",
"Action":[
"s3:GetObject"
],
"Resource":"arn:aws:s3:::yourBucket/*"
}
]
}

Answer 3

You must include an explicit callback at the end of your lambda or it'll stop running automatically before your s3 callback function ever gets hit.
As an example:
module.exports.getS3Object = async (event, context, callback) => {
const AWS = require('aws-sdk');
const S3 = new AWS.S3();
S3.getObject({ Bucket: "exampleBucket", Key: "exampleKey" })
.promise()
.then(data => console.log("finished"))
.catch(err => console.log("there was an error" + err))
callback(null, {statusCode: "200", body:"yay"}); //MUST INCLUDE
}