Listen to S3 event, read the file, and publish to an SNS topic

lamdaReadFileAndPublishSNS.js

var AWS = require('aws-sdk');
var s3 = new AWS.S3(); 
var sns = new AWS.SNS(); 

exports.handler = (event, context, callback) => { 
  var bucketName = process.env.bucketName; 
  var keyName = event.Records[0].s3.object.key; 
  readFile(bucketName, keyName, readFileContent, onError); 
};

function readFile (bucketName, filename, readFileContent, onError) { 
  var params = { 
    Bucket: bucketName, 
    Key: filename 
  };
  
  // 
  s3.getObject(params, function (err, data) { 
    if (!err) readFileContent(filename, data.Body.toString()); 
    else console.log(err); 
  }); 
} 
    
function readFileContent(filename, content) { 
  sns.publish({ 
    Message: content, 
    TopicArn: process.env.topicArn 
  }, function(err, data) { 
    if (err) { 
      console.log(err.stack); 
      return; 
    } 
    console.log('push sent'); 
    // context.done(null, 'Function Finished!'); 
  }); 
} 

function onError (err) { 
  console.log('error: ' + err); 
}