feat: Added Log info when agent run is cancelled and log warning if putting sentinel on queue fails during cleanup avoiding silent error suppression

PiperOrigin-RevId: 939668348

Author: google-genai-bot

src/google/adk/agents/parallel_agent.py

@@ -17,6 +17,7 @@
 from __future__ import annotations
 
 import asyncio
+import logging
 import sys
 from typing import AsyncGenerator
 from typing import ClassVar
@@ -32,6 +33,8 @@
 from .invocation_context import InvocationContext
 from .parallel_agent_config import ParallelAgentConfig
 
+logger = logging.getLogger('google_adk.' + __name__)
+
 
 def _create_branch_ctx_for_sub_agent(
     agent: BaseAgent,
@@ -65,9 +68,15 @@ async def process_an_agent(events_for_one_agent):
         await queue.put((event, resume_signal))
         # Wait for upstream to consume event before generating new events.
         await resume_signal.wait()
+    except asyncio.CancelledError:
+      logger.info('Agent run cancelled.')
+      raise
     finally:
       # Mark agent as finished.
-      await queue.put((sentinel, None))
+      try:
+        await queue.put((sentinel, None))
+      except Exception as e:
+        logger.warning('Failed to put sentinel on queue: %s', e)
 
   async with asyncio.TaskGroup() as tg:
     for events_for_one_agent in agent_runs: