Fixes #81 - Add TTL sessions

libs/langgraph-checkpoint-mongodb/langgraph/checkpoint/mongodb/aio.py

@@ -5,6 +5,7 @@
 import sys
 from collections.abc import AsyncIterator, Iterator, Sequence
 from contextlib import asynccontextmanager
+from datetime import datetime
 from importlib.metadata import version
 from typing import Any, Optional
 
@@ -81,6 +82,7 @@ def __init__(
         db_name: str = "checkpointing_db",
         checkpoint_collection_name: str = "checkpoints_aio",
         writes_collection_name: str = "checkpoint_writes_aio",
+        ttl: Optional[int] = None,
         **kwargs: Any,
     ) -> None:
         super().__init__()
@@ -90,6 +92,7 @@ def __init__(
         self.writes_collection = self.db[writes_collection_name]
         self._setup_future: asyncio.Future | None = None
         self.loop = asyncio.get_running_loop()
+        self.ttl = ttl
 
     async def _setup(self) -> None:
         """Create indexes if not present."""
@@ -107,6 +110,11 @@ async def _setup(self) -> None:
                 keys=[("thread_id", 1), ("checkpoint_ns", 1), ("checkpoint_id", -1)],
                 unique=True,
             )
+            if self.ttl:
+                await self.checkpoint_collection.create_index(
+                    keys=[("created_at", 1)],
+                    expireAfterSeconds=self.ttl,
+                )
         if isinstance(self.client, AsyncMongoClient):
             num_indexes = len(
                 await (await self.writes_collection.list_indexes()).to_list()  # type:ignore[misc]
@@ -124,6 +132,11 @@ async def _setup(self) -> None:
                 ],
                 unique=True,
             )
+            if self.ttl:
+                await self.writes_collection.create_index(
+                    keys=[("created_at", 1)],
+                    expireAfterSeconds=self.ttl,
+                )
         self._setup_future.set_result(None)
 
     @classmethod
@@ -134,6 +147,7 @@ async def from_conn_string(
         db_name: str = "checkpointing_db",
         checkpoint_collection_name: str = "checkpoints_aio",
         writes_collection_name: str = "checkpoint_writes_aio",
+        ttl: Optional[int] = None,
         **kwargs: Any,
     ) -> AsyncIterator[AsyncMongoDBSaver]:
         """Create asynchronous checkpointer
@@ -153,6 +167,7 @@ async def from_conn_string(
                 db_name,
                 checkpoint_collection_name,
                 writes_collection_name,
+                ttl,
                 **kwargs,
             )
             await saver._setup()
@@ -343,6 +358,8 @@ async def aput(
             "checkpoint_ns": checkpoint_ns,
             "checkpoint_id": checkpoint_id,
         }
+        if self.ttl:
+            doc["created_at"] = datetime.now()
         # Perform your operations here
         await self.checkpoint_collection.update_one(
             upsert_query, {"$set": doc}, upsert=True
@@ -389,6 +406,8 @@ async def aput_writes(
                 "task_path": task_path,
                 "idx": WRITES_IDX_MAP.get(channel, idx),
             }
+            if self.ttl:
+                upsert_query["created_at"] = datetime.now()
             type_, serialized_value = self.serde.dumps_typed(value)
             operations.append(
                 UpdateOne(

libs/langgraph-checkpoint-mongodb/langgraph/checkpoint/mongodb/saver.py

@@ -1,13 +1,14 @@
 from collections.abc import Iterator, Sequence
 from contextlib import contextmanager
+from datetime import datetime
 from importlib.metadata import version
 from typing import (
     Any,
     Optional,
 )
 
 from langchain_core.runnables import RunnableConfig
-from pymongo import MongoClient, UpdateOne
+from pymongo import ASCENDING, MongoClient, UpdateOne
 from pymongo.database import Database as MongoDatabase
 from pymongo.driver_info import DriverInfo
 
@@ -39,6 +40,7 @@ class MongoDBSaver(BaseCheckpointSaver):
         db_name (Optional[str]): Database name
         checkpoint_collection_name (Optional[str]): Name of Collection of Checkpoints
         writes_collection_name (Optional[str]): Name of Collection of intermediate writes.
+        ttl (Optional[int]): Time to live in seconds. See https://www.mongodb.com/docs/manual/core/index-ttl/.
 
     Examples:
 
@@ -69,20 +71,28 @@ def __init__(
         db_name: str = "checkpointing_db",
         checkpoint_collection_name: str = "checkpoints",
         writes_collection_name: str = "checkpoint_writes",
+        ttl: Optional[int] = None,
         **kwargs: Any,
     ) -> None:
         super().__init__()
         self.client = client
         self.db = self.client[db_name]
         self.checkpoint_collection = self.db[checkpoint_collection_name]
         self.writes_collection = self.db[writes_collection_name]
+        self.ttl = ttl
 
         # Create indexes if not present
         if len(self.checkpoint_collection.list_indexes().to_list()) < 2:
             self.checkpoint_collection.create_index(
                 keys=[("thread_id", 1), ("checkpoint_ns", 1), ("checkpoint_id", -1)],
                 unique=True,
             )
+            if self.ttl:
+                self.checkpoint_collection.create_index(
+                    keys=[("created_at", ASCENDING)],
+                    expireAfterSeconds=self.ttl,
+                )
+
         if len(self.writes_collection.list_indexes().to_list()) < 2:
             self.writes_collection.create_index(
                 keys=[
@@ -94,6 +104,11 @@ def __init__(
                 ],
                 unique=True,
             )
+            if self.ttl:
+                self.writes_collection.create_index(
+                    keys=[("created_at", ASCENDING)],
+                    expireAfterSeconds=self.ttl,
+                )
 
     @classmethod
     @contextmanager
@@ -103,6 +118,7 @@ def from_conn_string(
         db_name: str = "checkpointing_db",
         checkpoint_collection_name: str = "checkpoints",
         writes_collection_name: str = "checkpoint_writes",
+        ttl: Optional[int] = None,
         **kwargs: Any,
     ) -> Iterator["MongoDBSaver"]:
         """Context manager to create a MongoDB checkpoint saver.
@@ -119,6 +135,7 @@ def from_conn_string(
             db_name: Database name. It will be created if it doesn't exist.
             checkpoint_collection_name: Checkpoint Collection name. Created if it doesn't exist.
             writes_collection_name: Collection name of intermediate writes. Created if it doesn't exist.
+            ttl (Optional[int]): Time to live in seconds.
         Yields: A new MongoDBSaver.
         """
         client: Optional[MongoClient] = None
@@ -134,6 +151,7 @@ def from_conn_string(
                 db_name,
                 checkpoint_collection_name,
                 writes_collection_name,
+                ttl,
                 **kwargs,
             )
         finally:
@@ -361,6 +379,9 @@ def put(
             "checkpoint_ns": checkpoint_ns,
             "checkpoint_id": checkpoint_id,
         }
+        if self.ttl:
+            upsert_query["created_at"] = datetime.now()
+
         self.checkpoint_collection.update_one(upsert_query, {"$set": doc}, upsert=True)
         return {
             "configurable": {
@@ -403,6 +424,9 @@ def put_writes(
                 "task_path": task_path,
                 "idx": WRITES_IDX_MAP.get(channel, idx),
             }
+            if self.ttl:
+                upsert_query["created_at"] = datetime.now()
+
             type_, serialized_value = self.serde.dumps_typed(value)
             operations.append(
                 UpdateOne(

libs/langgraph-checkpoint-mongodb/tests/unit_tests/test_sync.py

@@ -1,4 +1,5 @@
 import os
+from time import sleep
 from typing import Any
 
 import pytest
@@ -165,3 +166,39 @@ def test_nested_filter() -> None:
         # Drop collections
         saver.checkpoint_collection.drop()
         saver.writes_collection.drop()
+
+
+def test_ttl(input_data: dict[str, Any]) -> None:
+    collection_name = "ttl_test"
+    ttl = 1
+
+    # Set period between background task runs
+    monitor_period = 2
+    client: MongoClient = MongoClient(MONGODB_URI)
+    client.admin.command("setParameter", 1, ttlMonitorSleepSecs=monitor_period)
+
+    with MongoDBSaver.from_conn_string(
+        MONGODB_URI, DB_NAME, collection_name, ttl=ttl
+    ) as saver:
+        try:
+            # save a checkpoint
+            saver.put(
+                input_data["config_2"],
+                input_data["chkpnt_2"],
+                input_data["metadata_2"],
+                {},
+            )
+
+            query: dict[str, Any] = {}  # search by no keys, return all checkpoints
+            search_results_2 = list(saver.list(None, filter=query))
+            assert len(search_results_2) == 1
+            assert search_results_2[0].metadata == input_data["metadata_2"]
+
+            sleep(ttl + monitor_period)
+            assert len(list(saver.list(None, filter=query))) == 0
+
+        finally:
+            saver.checkpoint_collection.delete_many({})
+            saver.checkpoint_collection.drop_indexes()
+            saver.writes_collection.delete_many({})
+            saver.writes_collection.drop_indexes()