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fix: remove monotonic_timestamp #526

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fix: remove monotonic_timestamp #526

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33f1f4b
fix: remove monotonic_timestamp
thayinm Jun 16, 2026
ee3e8e9
Merge branch 'main' into main
thayinm Jun 24, 2026
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47 changes: 7 additions & 40 deletions src/bedrock_agentcore/memory/integrations/strands/session_manager.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@
import logging
import threading
from concurrent.futures import ThreadPoolExecutor, as_completed
from datetime import datetime, timedelta, timezone
from datetime import datetime, timezone
from enum import Enum
from typing import TYPE_CHECKING, Any, Dict, NamedTuple, Optional

Expand Down Expand Up @@ -98,38 +98,6 @@ class AgentCoreMemorySessionManager(RepositorySessionManager, SessionRepository)
- Consistent with existing Strands Session managers (such as: FileSessionManager, S3SessionManager)
"""

# Class-level timestamp tracking for monotonic ordering
_timestamp_lock = threading.Lock()
_last_timestamp: Optional[datetime] = None

@classmethod
def _get_monotonic_timestamp(cls, desired_timestamp: Optional[datetime] = None) -> datetime:
"""Get a monotonically increasing timestamp.

Args:
desired_timestamp (Optional[datetime]): The desired timestamp. If None, uses current time.

Returns:
datetime: A timestamp guaranteed to be greater than any previously returned timestamp.
"""
if desired_timestamp is None:
desired_timestamp = datetime.now(timezone.utc)

with cls._timestamp_lock:
if cls._last_timestamp is None:
cls._last_timestamp = desired_timestamp
return desired_timestamp

# Why the 1 second check? Because Boto3 does NOT support sub 1 second resolution.
if desired_timestamp <= cls._last_timestamp + timedelta(seconds=1):
# Increment by 1 second to ensure ordering
new_timestamp = cls._last_timestamp + timedelta(seconds=1)
else:
new_timestamp = desired_timestamp

cls._last_timestamp = new_timestamp
return new_timestamp

def __init__(
self,
agentcore_memory_config: AgentCoreMemoryConfig,
Expand Down Expand Up @@ -282,7 +250,7 @@ def create_session(self, session: Session, **kwargs: Any) -> Session:
payload=[
{"blob": json.dumps(session.to_dict())},
],
eventTimestamp=self._get_monotonic_timestamp(),
eventTimestamp=datetime.now(timezone.utc),
metadata={STATE_TYPE_KEY: {"stringValue": StateType.SESSION.value}},
)
logger.info("Created session: %s with event: %s", session.session_id, event.get("event", {}).get("eventId"))
Expand Down Expand Up @@ -414,7 +382,7 @@ def create_agent(self, session_id: str, session_agent: SessionAgent, **kwargs: A
payload=[
{"blob": json.dumps(session_agent.to_dict())},
],
eventTimestamp=self._get_monotonic_timestamp(),
eventTimestamp=datetime.now(timezone.utc),
metadata={
STATE_TYPE_KEY: {"stringValue": StateType.AGENT.value},
AGENT_ID_KEY: {"stringValue": session_agent.agent_id},
Expand Down Expand Up @@ -582,7 +550,6 @@ def create_message(

# Parse the original timestamp and use it as desired timestamp
original_timestamp = datetime.fromisoformat(session_message.created_at.replace("Z", "+00:00"))
monotonic_timestamp = self._get_monotonic_timestamp(original_timestamp)

if self.config.batch_size > 1:
# Buffer the pre-processed message
Expand All @@ -593,7 +560,7 @@ def create_message(
session_id=session_id,
messages=messages,
is_blob=is_blob,
timestamp=monotonic_timestamp,
timestamp=original_timestamp,
metadata=merged_metadata,
)
)
Expand All @@ -613,7 +580,7 @@ def create_message(
actor_id=self.config.actor_id,
session_id=session_id,
messages=messages,
event_timestamp=monotonic_timestamp,
event_timestamp=original_timestamp,
metadata=merged_metadata,
)
else:
Expand All @@ -622,7 +589,7 @@ def create_message(
"actorId": self.config.actor_id,
"sessionId": session_id,
"payload": [{"blob": json.dumps(messages[0])}],
"eventTimestamp": monotonic_timestamp,
"eventTimestamp": original_timestamp,
}
if merged_metadata:
create_event_kwargs["metadata"] = merged_metadata
Expand Down Expand Up @@ -1177,7 +1144,7 @@ def _flush_agent_states_only(self) -> list[dict[str, Any]]:
actorId=self.config.actor_id,
sessionId=self.config.session_id,
payload=payloads,
eventTimestamp=self._get_monotonic_timestamp(),
eventTimestamp=datetime.now(timezone.utc),
metadata={
STATE_TYPE_KEY: {"stringValue": StateType.AGENT.value},
AGENT_ID_KEY: {"stringValue": agent_id},
Expand Down