improve client's lease monitoring

we monitor lease status too frequently (every 5s) which doesn't correspond to the default grpc keepalive which we just made longer.
Let's lighten the load a bit and poll less frequent, once in 30s.
Changed the info message about lease expiring son to more friendly "ending in 5 minutes".
Also, once controller starts providing end time this will use the controller's timestamp. Until then fall back to the locally calculated begin time + duration.

Author: michalskrivanek

packages/jumpstarter/jumpstarter/client/lease.py

@@ -248,23 +248,25 @@ async def _wait_for_ready_connection(self, path: str):
     @asynccontextmanager
     async def monitor_async(self, threshold: timedelta = timedelta(minutes=5)):
         async def _monitor():
+            check_interval = 30  # seconds - check periodically for external lease changes
             while True:
                 lease = await self.get()
-                # TODO: use effective_end_time as the authoritative source for lease end time
                 if lease.effective_begin_time:
-                    end_time = lease.effective_begin_time + lease.duration
+                    # Calculate end time from effective_end_time or fallback to begin_time + duration
+                    end_time = lease.effective_end_time
+                    if not end_time or end_time.timestamp() == 0:
+                        end_time = lease.effective_begin_time + lease.duration
+
                     remain = end_time - datetime.now(tz=datetime.now().astimezone().tzinfo)
                     if remain < timedelta(0):
                         # lease already expired, stopping monitor
                         logger.info("Lease {} ended at {}".format(self.name, end_time))
                         break
-                    elif remain < threshold:
-                        # lease expiring soon, check again on expected expiration time in case it's extended
-                        logger.info("Lease {} ending soon in {} at {}".format(self.name, remain, end_time))
-                        await sleep(threshold.total_seconds())
-                    else:
-                        # lease still active, check again in 5 seconds
-                        await sleep(5)
+                    # Log once when entering the threshold window
+                    if threshold - timedelta(seconds=check_interval) <= remain < threshold:
+                        logger.info("Lease {} ending in {} minutes at {}".format(
+                            self.name, int((remain.total_seconds() + 30) // 60), end_time))
+                    await sleep(min(remain.total_seconds(), check_interval))
                 else:
                     await sleep(1)