refresh drives config credentials using a timer

Author: gogakoreli

jupyter_drives/base.py

@@ -4,10 +4,14 @@
 from traitlets import Enum, Unicode, default
 from traitlets.config import Configurable
 import boto3
+from tornado.ioloop import PeriodicCallback
 
 # Supported third-party services
 MANAGERS = {}
 
+# 15 minutes
+CREDENTIALS_REFRESH = 15 * 60 * 1000
+
 # Moved to the architecture of having one provider independent manager.
 # Keeping the loop in case of future developments that need this feature.
 for entry in entrypoints.get_group_all("jupyter_drives.manager_v1"):
@@ -19,6 +23,7 @@
 class DrivesConfig(Configurable):
     """
     Allows configuration of supported drives via jupyter_notebook_config.py
+    Implements singleton pattern
     """
 
     session_token = Unicode(
@@ -48,7 +53,7 @@ class DrivesConfig(Configurable):
         allow_none=True,
         help = "Region name.",
     )
-    
+
     api_base_url = Unicode(
         config=True,
         help="Base URL of the provider service REST API.",
@@ -59,7 +64,7 @@ def set_default_api_base_url(self):
         # for AWS S3 drives
         if self.provider == "s3":
             return "https://s3.amazonaws.com/" # region? https://s3.<region>.amazonaws.com/
-        
+
         # for Google Cloud Storage drives
         elif self.provider == "gcs":
             return "https://www.googleapis.com/"   
@@ -71,15 +76,34 @@ def set_default_api_base_url(self):
         help="The source control provider.",
     )
 
+    _instance = None
+
+    def __new__(cls, **kwargs):
+        if cls._instance is None:
+            cls._instance = super(DrivesConfig, cls).__new__(cls)
+            cls._instance._initialized = False
+        return cls._instance
+
     def __init__(self, **kwargs):
+        if self._initialized:
+            return
+
         super().__init__(**kwargs)
-        self._load_credentials()
-    
-    def _load_credentials(self):  
+        self._initialize_credentials_refresh()
+        self._initialized = True
+
+    def _initialize_credentials_refresh(self):
         # check if credentials were already set in jupyter_notebook_config.py
         if self.access_key_id is not None and self.secret_access_key is not None:
             return
-        
+
+        self._load_credentials()
+        self._credential_refresh = PeriodicCallback(
+            self._load_credentials, CREDENTIALS_REFRESH
+        )
+        self._credential_refresh.start()
+
+    def _load_credentials(self):
         # automatically extract credentials for S3 drives
         try:
             s = boto3.Session()
@@ -110,4 +134,4 @@ def _load_credentials(self):
         self.access_key_id = c.access_key
         self.secret_access_key = c.secret_key
         self.region_name = s.region_name
-        self.session_token = c.token
+        self.session_token = c.token