AWS Lambda Node Js JSON Undefined

Question

I am trying to create an AWS Lambda trigger that sends email to a user. The Lambda is triggered by SQS, where I will be pushing my messages from my code. Now when I am using test cases on Lambda, everything is working fine, but when I am sending json data over SQS (which is sent to by using python), all the fields are shown as undefined. Following is my Lambda code:

var aws = require('aws-sdk');
var ses = new aws.SES({region: 'ap-south-1'});

var RECEIVER = 'xxxxxxx@xxxx.com';
var SENDER = 'yyyyyyy@yyyy.com';

var response = {
 "isBase64Encoded": false,
 "headers": { 'Content-Type': 'application/json', 'Access-Control-Allow-Origin': '*'},
 "statusCode": 200,
 "body": "{\"result\": \"Success.\"}"
 };
 

exports.handler = (event, context, callback) => {
    
 var params = {
    Destination: {
        ToAddresses: [
                RECEIVER
            ]
    },
    Message: {
        Body: {
            Text: {
                Data: 'My Name is ' + event.user +'\nTimestamp:'+ event.timestamp,
                Charset: 'UTF-8'
            }
        },
        Subject: {
            Data: 'Test : ' + event.name,
            Charset: 'UTF-8'
        }
    },
    Source: SENDER
};


 ses.sendEmail(params, function (err, data) {
    callback(null, {err: err, data: data});
    if (err) {
        console.log(err);
        context.fail(err);
    } else {
        
        console.log(data);
        context.succeed(event);
    }
});
};

My Python File:

class SQSQueue(object):
    def __init__(self, queueName=None):
        self.resource = boto3.resource('sqs',region_name="xxxxxxx")
        self.queue = self.resource.get_queue_by_name(QueueName=AWS_SQS_QUEUE_NAME)
        self.QueueName = queueName
    
    def send(self, Message={}):
        data = json.dumps(Message)
        response = self.queue.send_message(MessageBody=data)
        return response
    
    
if __name__ == '__main__':
    q = SQSQueue(queueName=AWS_SQS_QUEUE_NAME)
    name = "xxxxxxx"
    timestamp = "yyyyyyyy"
    message = {
        "user": name,
        "timestamp": timestamp
    }
    
    response = q.send(Message=message)

I am not a node developer, and have no knowledge of the language, I just followed a couple of posts/videos and developed this.

Posts I referred for this query: AWS Lambda Javascript JSON object undefined AWS Lambda with API Gateway throwing response error

Output I am getting on my email:

My Name is undefined
Timestamp:undefined

Answer 1

Payload of the sqs in not directly your message, it wraps also other details.

You have an array of records, so to get payload of your message try

event.Records.map(record => {
  const message = JSON.parse(record.body);
  // message.name , message.timestamp  ....
  processMessage(message);
});

It could be setup how many records to be received by the lambda using batch size https://docs.aws.amazon.com/lambda/latest/dg/API_CreateEventSourceMapping.html (BatchSize)

Answer 2

I think something is not right with the processing of the your messages. The lambda will always process a list of records (which correspond to messages) instead of processing one message at a time.

You can check here what you cant expect on the event https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html

{
    "Records": [
        {
            "messageId": "059f36b4-87a3-44ab-83d2-661975830a7d",
            "receiptHandle": "AQEBwJnKyrHigUMZj6rYigCgxlaS3SLy0a...",
            "body": "Test message.",
            "attributes": {
                "ApproximateReceiveCount": "1",
                "SentTimestamp": "1545082649183",
                "SenderId": "AIDAIENQZJOLO23YVJ4VO",
                "ApproximateFirstReceiveTimestamp": "1545082649185"
            },
            "messageAttributes": {},
            "md5OfBody": "e4e68fb7bd0e697a0ae8f1bb342846b3",
            "eventSource": "aws:sqs",
            "eventSourceARN": "arn:aws:sqs:us-east-2:123456789012:my-queue",
            "awsRegion": "us-east-2"
        },
        {
            "messageId": "2e1424d4-f796-459a-8184-9c92662be6da",
            "receiptHandle": "AQEBzWwaftRI0KuVm4tP+/7q1rGgNqicHq...",
            "body": "Test message.",
            "attributes": {
                "ApproximateReceiveCount": "1",
                "SentTimestamp": "1545082650636",
                "SenderId": "AIDAIENQZJOLO23YVJ4VO",
                "ApproximateFirstReceiveTimestamp": "1545082650649"
            },
            "messageAttributes": {},
            "md5OfBody": "e4e68fb7bd0e697a0ae8f1bb342846b3",
            "eventSource": "aws:sqs",
            "eventSourceARN": "arn:aws:sqs:us-east-2:123456789012:my-queue",
            "awsRegion": "us-east-2"
        }
    ]
}