Parse JSON file uploaded in S3 using Lambda - json

Question

I'm trying to parse a JSON file that get's uploaded in S3. I invoke the lambda function using an S3 PUT/POST method trigger.
I'm using the following code.. however i'm not able to parse the json file. Can someone please help me?
var aws = require('aws-sdk');
var s3 = new aws.S3();
exports.handler = async (event, context, callback) => {
var srcBucket = event.Records[0].s3.bucket.name;
var srcKey = event.Records[0].s3.object.key;
console.log("Params: srcBucket: " + srcBucket + " srcKey: " + srcKey + "\n");
var getParams = {
Bucket: srcBucket,
Key: srcKey,
};
s3.getObject(getParams, function (err, data) {
if (err) console.log(err, err.stack);
else {
console.log(JSON.stringify(data.Body.toString()));
}
});
};

Answer 1

Your code looks correct However, I'd suggest taking the example from AWS docs as your starting point. Since your Lambda handler is an async handler, you have to await the promise returned by s3.getObject() , otherwise your function will complete before the callback executes (see the example code from the link).
Since you mention that your Lambda function cannot parse the file, I assume the function gets invoked by S3 trigger (i.e. you can see the console.log('Params: ...) line in Cloudwatch Logs). If that's not the case, first check that the S3 trigger is configured correctly and S3 has permission to invoke the Lambda function. If you created the function via AWS Console, this permission would have been set automatically.
The next step I'd suggest is to check the Lambda function's IAM role. Check if the IAM role has s3:GetObject permission for your bucket and all objects under it or for the specific prefix you have configured S3 notification (e.g. <bucket>/* or <bucket>/prefix/*).
If the Lambda IAM permissions are correct, you'll have to check S3 bucket policies. I suspect you haven't set up bucket policies according to what you describe.