CODEWITHSUNDEEP
javascriptamazon-web-servicesamazon-s3aws-lambda
Calvin
Calvin

Reputation: 417

s3 object metadata lambda function

I am new to javascript and I am trying to write a lambda function that would get triggered by PUT event in the bucket, the function would write the file name and some metadata field that's on the s3 object to the dynamodb table. I have most of it worked out but I'm stuck at grabbing the x-amz-meta header info and pass the variable to dynamo.put parameter. Can anyone tell me what I am doing wrong in my code? thanks!

var AWS = require('aws-sdk');
var dynamo = new AWS.DynamoDB.DocumentClient({region: 'us-east-1'});
var s3 = new AWS.S3();
//specify the parameters from event to write to specified db table
exports.handler = function(event, context, callback) {
  var srcKey = unescape(event.Records[0].s3.object.key);
  var srcEtag = unescape(event.Records[0].s3.object.eTag);
  var scrUploadTime = unescape(event.Records[0].eventTime);
  var bucket= unescape(event.Records[0].s3.bucket.name);
  var checksum =

      s3.headObject(
        {
            Bucket: bucket,
            Key: srcKey
        },
        function(err, data)
        {
            if (err)
            {
                console.log(err);
                context.done('Error', 'Error getting s3 object: ' + err);
            }
            else
            {
                 return console.log(this.httpResponse.headers['x-amz-meta-checksum']);
            }
        });

    var params = {  
        Item: {
            filename: srcKey,
            uploadtime: scrUploadTime,
            client_checksum : checksum
        },
        TableName: 'S3_log'
        };

//write to dynammodb
dynamo.put(params, function(err, data){
        if (err) {
            callback(err, null);
        }else{
            callback(null, data);
        }
    });
};

Upvotes: 5

Views: 3753

Answers (1)

Michael - sqlbot
Michael - sqlbot

Reputation: 178956

It looks like you want this:

console.log(data.Metadata['x-amz-meta-checksum']);

http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#headObject-property

But also, note that your code doesn't appear to be structured correctly. s3.headObject is asynchronous so your code continues execution at var params = ... before s3.headObject returns. The next actions should probably be inside the callback or handled in another way (waterfall, promises, etc.) to delay the next action until this one completes.

Upvotes: 3

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