Keep auth session alive when inactive

Author: fqqb

yamcs-client/src/yamcs/client/core.py

@@ -155,6 +155,7 @@ def __init__(
         tls_verify: Union[bool, str] = True,
         credentials: Optional[Credentials] = None,
         user_agent: Optional[str] = None,
+        keep_alive: bool = True,
         on_token_update: Optional[Callable[[Credentials], None]] = None,
     ):
         """
@@ -172,6 +173,13 @@ def __init__(
             Credentials for when the server is secured
         :param user_agent:
             Optionally override the default user agent
+        :param keep_alive:
+            Automatically renew the client session. If disabled,
+            the session will terminate after about 30 minutes of
+            inactivity.
+
+            This property is only considered when accessing a
+            server that requires authentication.
         """
 
         # Allow server URLs.
@@ -190,6 +198,7 @@ def __init__(
             user_agent=user_agent,
             on_token_update=on_token_update,
             tls_verify=tls_verify,
+            keep_alive=keep_alive,
         )
 
     @staticmethod

yamcs-client/src/yamcs/core/context.py

@@ -1,3 +1,4 @@
+from datetime import datetime, timezone
 from typing import Callable, Optional, Union
 
 import requests
@@ -7,11 +8,11 @@
 from yamcs.api import exception_pb2
 from yamcs.core.auth import Credentials
 from yamcs.core.exceptions import NotFound, Unauthorized, YamcsError
-from yamcs.core.helpers import do_request
+from yamcs.core.helpers import FixedDelay, do_request
 
 
 class Context:
-    credentials = None
+    credentials: Optional[Credentials] = None
 
     def __init__(
         self,
@@ -21,6 +22,7 @@ def __init__(
         user_agent: Optional[str] = None,
         on_token_update: Optional[Callable[[Credentials], None]] = None,
         tls_verify: Union[bool, str] = True,
+        keep_alive: bool = True,
     ):
         if address.endswith("/"):
             self.address = address[:-1]
@@ -51,9 +53,23 @@ def __init__(
                 urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
 
         if credentials:
-            self.credentials = credentials.login(
+            converted_creds = credentials.login(
                 self.session, self.auth_root, on_token_update
             )
+            self.credentials = converted_creds
+
+            # An assigned refresh token lives only for about 30 minutes. We actively
+            # extend it, so that the session survives when idle.
+            if converted_creds.expiry and keep_alive:
+
+                def renew_session():
+                    expiry = converted_creds.expiry
+                    if expiry:
+                        remaining = expiry - datetime.now(tz=timezone.utc)
+                        if 0 < remaining.total_seconds() < 60:
+                            converted_creds.refresh(self.session, self.auth_root)
+
+                self._session_renewer = FixedDelay(renew_session, 10)
 
         if not user_agent:
             user_agent = "python-yamcs-client v" + clientversion.__version__
@@ -121,4 +137,8 @@ def request(self, method: str, path: str, **kwargs) -> requests.Response:
 
     def close(self):
         """Close this context"""
+
+        if self._session_renewer:
+            self._session_renewer.stop()
+
         self.session.close()

yamcs-client/src/yamcs/core/helpers.py

@@ -4,7 +4,8 @@
 import logging
 import os
 from datetime import datetime, timezone
-from typing import Any, Iterator, List, Union
+from threading import Timer
+from typing import Any, Callable, Iterator, List, Union
 from urllib.parse import urlparse
 
 import requests
@@ -359,3 +360,34 @@ def clear(self):
         copy = list(repeatable)
         for item in copy:
             repeatable.remove(item)
+
+
+class FixedDelay:
+    """
+    Helper class to run a periodic action, with a fixed delay between
+    the termination of one execution, and the commencement of the next.
+    """
+
+    def __init__(self, action: Callable[[], None], period: float):
+        self._timer = None
+        self.action = action
+        self.period = period
+        self.is_running = False
+        self.start()
+
+    def start(self):
+        if not self.is_running:
+            self._timer = Timer(self.period, self._run)
+            self._timer.daemon = True
+            self._timer.start()
+            self.is_running = True
+
+    def stop(self):
+        if self._timer:
+            self._timer.cancel()
+        self.is_running = False
+
+    def _run(self):
+        self.is_running = False
+        self.start()
+        self.action()