s3.js

var BUCKET_NAME = "logs";
var LOG_FILE_NAME = "log_file.log";
var LOG_FILE_PATH = "./var/logs/" + LOG_FILE_NAME;

var AWS = require('aws-sdk');
var fs = require('fs');

AWS.config.loadFromPath('./config.json');

exports.uploadLog = function(callback) {
  fs.readFile(LOG_FILE_PATH, function(err,data){
    if (err) { throw err; }
      var s3 = new AWS.S3();
      var params = {
        Bucket: BUCKET_NAME,
        Key: LOG_FILE_NAME,
        Body: data,
        ACL: 'private'
      };
      s3.putObject(params, function(err, res) {
       if (err) callback(err);
       else callback(null, res);
      });
    });
};

upload.js

var S3 = require('../lib/s3');

exports.uploadLog = function(req, res) {
    S3.uploadFile(function(error, data){
      if (error) {
        console.log(error);
        res.json({ "status": "failure", "error": error });
      } else {
        res.json({"status": "ok"});
      }
    });
};