diff --git a/runtimes/sidecar/sidecar.py b/runtimes/sidecar/sidecar.py
index f7f766b5..507d92f9 100644
--- a/runtimes/sidecar/sidecar.py
+++ b/runtimes/sidecar/sidecar.py
@@ -12,7 +12,10 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 
+import logging
 import os
+import sys
+import zipfile
 
 from flask import Flask
 from flask import make_response
@@ -21,21 +24,32 @@ from oslo_concurrency import lockutils
 import requests
 
 app = Flask(__name__)
+ch = logging.StreamHandler(sys.stdout)
+ch.setLevel(logging.DEBUG)
+ch.setFormatter(logging.Formatter('%(asctime)s - %(levelname)s - %(message)s'))
+del app.logger.handlers[:]
+app.logger.addHandler(ch)
 
 DOWNLOAD_ERROR = "Failed to download function package from %s, error: %s"
 
 
+def log(message, level="info"):
+    global app
+    log_func = getattr(app.logger, level)
+    log_func(message)
+
+
 @lockutils.synchronized('download_function', external=True,
                         lock_path='/var/lock/qinling')
-def _download_package(url, zip_file, token=None):
-    """Download package as needed.
+def _download_package(url, zip_file, token=None, unzip=None):
+    """Download package and unzip as needed.
 
     Return None if successful otherwise a Flask.Response object.
     """
     if os.path.isfile(zip_file):
         return None
 
-    print('Downloading function, download_url:%s' % url)
+    log("Start downloading function")
 
     headers = {}
     if token:
@@ -50,26 +64,41 @@ def _download_package(url, zip_file, token=None):
         with open(zip_file, 'wb') as fd:
             for chunk in r.iter_content(chunk_size=65535):
                 fd.write(chunk)
+
+        log("Downloaded function package to %s" % zip_file)
+
+        if unzip:
+            dest = zip_file.split('.')[0]
+            with open(zip_file, 'rb') as f:
+                zf = zipfile.ZipFile(f)
+                zf.extractall(dest)
+            log("Unzipped")
     except Exception as e:
         return make_response(DOWNLOAD_ERROR % (url, str(e)), 500)
 
-    print('Downloaded function package to %s' % zip_file)
-
 
 @app.route('/download', methods=['POST'])
 def download():
     """Download function package to a shared folder.
 
     The parameters 'download_url' and 'function_id' need to be specified
-    explicitly. It's guaranteed in the server side.
+    explicitly. It's guaranteed on the server side.
+
+    :param download_url: The URL for function package download. It's a Qinling
+        function resource URL with 'download' enabled.
+    :param function_id: Function ID.
+    :param token: Optional. The token used for download.
+    :param unzip: Optional. If unzip is needed after download.
     """
     params = request.get_json()
     zip_file = '/var/qinling/packages/%s.zip' % params['function_id']
+    log("Function package download request received, params: %s" % params)
 
     resp = _download_package(
         params['download_url'],
         zip_file,
-        params.get('token')
+        token=params.get('token'),
+        unzip=params.get('unzip')
     )
 
     return resp if resp else 'downloaded'