implement sts_token_buffer_time attribute for transport_options to up…

…date token earlier than expiration time

kombu/transport/SQS.py

@@ -76,7 +76,8 @@
         },
       }
     'sts_role_arn': 'arn:aws:iam::<xxx>:role/STSTest', # optional
-    'sts_token_timeout': 900 # optional
+    'sts_token_timeout': 900, # optional
+    'sts_token_buffer_time': 60 # optional
     }
 
 Note that FIFO and standard queues must be named accordingly (the name of
@@ -91,6 +92,9 @@
 sts_token_timeout. sts_role_arn is the assumed IAM role ARN we are trying
 to access with. sts_token_timeout is the token timeout, defaults (and minimum)
 to 900 seconds. After the mentioned period, a new token will be created.
+sts_token_buffer_time (seconds) is the time by which you want to refresh your token
+earlier than its actual expiration time, defaults to 0 (no time buffer will be added),
+should be less than sts_token_timeout.
 
 
 
@@ -136,7 +140,7 @@
 import socket
 import string
 import uuid
-from datetime import datetime
+from datetime import datetime, timedelta
 from queue import Empty
 
 from botocore.client import Config
@@ -765,34 +769,38 @@ def sqs(self, queue=None):
         )
         return c
 
+    def _refresh_sqs_client(self, queue, q):
+        sts_creds = self.generate_sts_session_token_with_buffer(
+            self.transport_options.get('sts_role_arn'),
+            self.transport_options.get('sts_token_timeout', 900),
+            self.transport_options.get('sts_token_buffer_time', 0),
+        )
+        self.sts_expiration = sts_creds['Expiration']
+        self._predefined_queue_clients[queue] = self.new_sqs_client(
+            region=q.get('region', self.region),
+            access_key_id=sts_creds['AccessKeyId'],
+            secret_access_key=sts_creds['SecretAccessKey'],
+            session_token=sts_creds['SessionToken'],
+        )
+        return self._predefined_queue_clients[queue]
+
     def _handle_sts_session(self, queue, q):
-        if not hasattr(self, 'sts_expiration'):  # STS token - token init
-            sts_creds = self.generate_sts_session_token(
-                self.transport_options.get('sts_role_arn'),
-                self.transport_options.get('sts_token_timeout', 900))
-            self.sts_expiration = sts_creds['Expiration']
-            c = self._predefined_queue_clients[queue] = self.new_sqs_client(
-                region=q.get('region', self.region),
-                access_key_id=sts_creds['AccessKeyId'],
-                secret_access_key=sts_creds['SecretAccessKey'],
-                session_token=sts_creds['SessionToken'],
-            )
-            return c
-        # STS token - refresh if expired
-        elif self.sts_expiration.replace(tzinfo=None) < datetime.utcnow():
-            sts_creds = self.generate_sts_session_token(
-                self.transport_options.get('sts_role_arn'),
-                self.transport_options.get('sts_token_timeout', 900))
-            self.sts_expiration = sts_creds['Expiration']
-            c = self._predefined_queue_clients[queue] = self.new_sqs_client(
-                region=q.get('region', self.region),
-                access_key_id=sts_creds['AccessKeyId'],
-                secret_access_key=sts_creds['SecretAccessKey'],
-                session_token=sts_creds['SessionToken'],
-            )
-            return c
-        else:  # STS token - ruse existing
-            return self._predefined_queue_clients[queue]
+        """
+        Refreshes the SQS client with a new token on STS token initialization
+        or expiration. Otherwise, using cached client.
+        """
+        if (
+            not hasattr(self, 'sts_expiration') or
+            self.sts_expiration.replace(tzinfo=None) < datetime.utcnow()
+        ):
+            return self._refresh_sqs_client(queue, q)
+        return self._predefined_queue_clients[queue]
+
+    def generate_sts_session_token_with_buffer(self, role_arn, token_expiry_seconds, token_buffer_seconds=0):
+        credentials = self.generate_sts_session_token(role_arn, token_expiry_seconds)
+        if token_buffer_seconds and token_buffer_seconds < token_expiry_seconds:
+            credentials["Expiration"] -= timedelta(seconds=token_buffer_seconds)
+        return credentials
 
     def generate_sts_session_token(self, role_arn, token_expiry_seconds):
         sts_client = boto3.client('sts')