diff --git a/lib/index.js b/lib/index.js
index 8986cb5..d27611f 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -15,6 +15,19 @@ var mime = require('mime');
 var StreamSink = require('streamsink');
 var PassThrough = require('stream').PassThrough;
 
+
+const log4js = require('log4js');
+log4js.configure({
+  appenders: {
+    app: { type: 'file', filename: 'application.log', flags: 'w', maxLogSize: '15M'}
+  },
+  categories: {
+    default: { appenders: ['app'], level: 'warn' }
+  }
+});
+
+var logger = log4js.getLogger();
+
 var MAX_PUTOBJECT_SIZE = 5 * 1024 * 1024 * 1024;
 var MAX_DELETE_COUNT = 1000;
 var MAX_MULTIPART_COUNT = 10000;
@@ -145,11 +158,14 @@ Client.prototype.uploadFile = function(params) {
   var localFileSlicer = null;
   var parts = [];
 
+  logger.info(`Uploading file - ${localFile}`);
   openFile();
 
   return uploader;
 
   function handleError(err) {
+    logger.error(`Issue while uploading local file - ${err}`);
+    logger.error(`${err.stack}`);
     if (localFileSlicer) {
       localFileSlicer.unref();
       localFileSlicer = null;
@@ -200,6 +216,7 @@ Client.prototype.uploadFile = function(params) {
         handleError(err);
         return;
       }
+      logger.info('Uploading using multipart upload');
       startMultipartUpload(multipartUploadSize);
     } else {
       doWithRetry(tryPuttingObject, self.s3RetryCount, self.s3RetryDelay, onPutObjectDone);
@@ -261,7 +278,10 @@ Client.prototype.uploadFile = function(params) {
     return function(cb) {
       doWithRetry(tryUploadPart, self.s3RetryCount, self.s3RetryDelay, function(err, data) {
         if (fatalError) return;
-        if (err) return handleError(err);
+        if (err) {
+          logger.error('Failed to upload part');
+          return handleError(err);
+        }
         uploader.emit('part', data);
         cb();
       });
@@ -308,7 +328,13 @@ Client.prototype.uploadFile = function(params) {
         inStream.pipe(multipartETag);
         s3Params.Body = multipartETag;
 
+        let gotCallback = false
         self.s3.uploadPart(extend({}, s3Params), function(err, data) {
+          if (gotCallback) {
+            logger.warn('AWS JS SDK called callback twice while uploading part');
+            return
+          }
+          gotCallback = true
           pendCb();
           if (fatalError || errorOccurred) return;
           if (err) {
@@ -406,7 +432,13 @@ Client.prototype.uploadFile = function(params) {
       inStream.pipe(multipartETag);
       s3Params.Body = multipartETag;
 
+      let gotCallback = false
       self.s3.putObject(s3Params, function(err, data) {
+        if (gotCallback) {
+            logger.warn('AWS JS SDK called callback twice while uploading object');
+            return
+        }
+        gotCallback = true
         pendCb();
         if (fatalError) return;
         if (err) {
@@ -571,6 +603,7 @@ Client.prototype.listObjects = function(params) {
     ee.emit('end');
   });
 
+
   ee.abort = function() {
     abort = true;
   };
@@ -578,7 +611,10 @@ Client.prototype.listObjects = function(params) {
   return ee;
 
   function findAllS3Objects(marker, prefix, cb) {
-    if (abort) return;
+    if (abort) {
+      logger.warn('Aborting find all s3 objects operation');
+      return;
+    }
     doWithRetry(listObjects, self.s3RetryCount, self.s3RetryDelay, function(err, data) {
       if (abort) return;
       if (err) return cb(err);
@@ -1057,9 +1093,15 @@ function syncDir(self, params, directionIsToS3) {
         s3ObjectCursor += 1;
         uploadLocalFile();
       } else {
+        logger.info(`Skipping this file - ${localFileStat.s3Path}`)
+        if(localFileStat.s3Path == s3Object.key) {
+          logger.info(`File ${localFileStat.s3Path} already present on S3`)
+        }
+        ee.emit('fileSkipped', localFileStat.size, localFileStat.path);
         skipThisOne();
       }
-    } else {
+    }
+    else {
       if (!localFileStat) {
         downloadS3Object();
       } else if (!s3Object) {
@@ -1232,19 +1274,40 @@ function syncDir(self, params, directionIsToS3) {
   }
 
   function handleError(err) {
-    if (fatalError) return;
+    if (fatalError) {
+        logger.error('Fatal error in handleError');
+        if(err) {
+          logger.error(`${err.stack}`);
+        }
+        return;
+    }
+    if(err) {
+      logger.error(`${err}`);
+      logger.error(`${err.stack}`);
+    }
+    logger.warn('Setting fatal error to true');
     fatalError = true;
     ee.emit('error', err);
   }
 
+  /*
+    Looks for existing files on S3. Files already present on
+    S3 are skipped
+   */
   function findAllS3Objects() {
+
+    logger.info('Starting to find objects on S3');
     var finder = self.listObjects(listObjectsParams);
-    finder.on('error', handleError);
+    finder.on('error', function(err) {
+      logger.error(`Failed while finding objects on S3 - ${err}`);
+      handleError(err);
+    });
     finder.on('data', function(data) {
       if (fatalError) return;
       ee.objectsFound += data.Contents.length;
       ee.emit('progress');
       data.Contents.forEach(function(object) {
+        logger.info(`Found S3 object - ${object.Key}`);
         if(!object.Key.endsWith('/')) {
           object.key = object.Key.substring(prefix.length);
           allS3Objects.push(object);
@@ -1390,6 +1453,7 @@ function doWithRetry(fn, tryCount, delay, cb) {
           if (tryIndex >= tryCount) {
             cb(err);
           } else {
+            logger.info('Retrying after 1 second');
             setTimeout(tryOnce, delay);
           }
         }
diff --git a/package.json b/package.json
index c4cf925..f763206 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@elucidatainc/s3-node-client",
-  "version": "4.5.0",
+  "version": "4.5.1",
   "description": "high level amazon s3 client. upload and download files and directories",
   "main": "lib/index.js",
   "scripts": {
@@ -41,7 +41,8 @@
     "mkdirp": "~0.5.0",
     "pend": "~1.2.0",
     "rimraf": "~2.2.8",
-    "streamsink": "~1.2.0"
+    "streamsink": "~1.2.0",
+    "log4js": "^6.5.2"
   },
   "bugs": {
     "url": "https://github.com/ElucidataInc/node-s3-client/issues"