"""Cassandra-based chat message history, based on cassIO."""
from __future__ import annotations
import json
import uuid
from typing import TYPE_CHECKING, Any, Dict, Iterable, List, Optional, Sequence
from langchain_community.utilities.cassandra import SetupMode
if TYPE_CHECKING:
from cassandra.cluster import Session
from cassio.table.table_types import RowType
from langchain_core.chat_history import BaseChatMessageHistory
from langchain_core.messages import (
BaseMessage,
message_to_dict,
messages_from_dict,
)
DEFAULT_TABLE_NAME = "message_store"
DEFAULT_TTL_SECONDS = None
def _rows_to_messages(rows: Iterable[RowType]) -> List[BaseMessage]:
message_blobs = [row["body_blob"] for row in rows][::-1]
items = [json.loads(message_blob) for message_blob in message_blobs]
messages = messages_from_dict(items)
return messages
[docs]
class CassandraChatMessageHistory(BaseChatMessageHistory):
"""Chat message history that is backed by Cassandra."""
[docs]
def __init__(
self,
session_id: str,
session: Optional[Session] = None,
keyspace: Optional[str] = None,
table_name: str = DEFAULT_TABLE_NAME,
ttl_seconds: Optional[int] = DEFAULT_TTL_SECONDS,
*,
setup_mode: SetupMode = SetupMode.SYNC,
) -> None:
"""
Initialize a new instance of CassandraChatMessageHistory.
Args:
session_id: arbitrary key that is used to store the messages
of a single chat session.
session: Cassandra driver session.
If not provided, it is resolved from cassio.
keyspace: Cassandra key space. If not provided, it is resolved from cassio.
table_name: name of the table to use.
ttl_seconds: time-to-live (seconds) for automatic expiration
of stored entries. None (default) for no expiration.
setup_mode: mode used to create the Cassandra table (SYNC, ASYNC or OFF).
"""
try:
from cassio.table import ClusteredCassandraTable
except (ImportError, ModuleNotFoundError):
raise ImportError(
"Could not import cassio python package. "
"Please install it with `pip install cassio`."
)
self.session_id = session_id
self.ttl_seconds = ttl_seconds
kwargs: Dict[str, Any] = {}
if setup_mode == SetupMode.ASYNC:
kwargs["async_setup"] = True
self.table = ClusteredCassandraTable(
session=session,
keyspace=keyspace,
table=table_name,
ttl_seconds=ttl_seconds,
primary_key_type=["TEXT", "TIMEUUID"],
ordering_in_partition="DESC",
skip_provisioning=setup_mode == SetupMode.OFF,
**kwargs,
)
@property
def messages(self) -> List[BaseMessage]: # type: ignore
"""Retrieve all session messages from DB"""
# The latest are returned, in chronological order
rows = self.table.get_partition(
partition_id=self.session_id,
)
return _rows_to_messages(rows)
[docs]
async def aget_messages(self) -> List[BaseMessage]:
"""Retrieve all session messages from DB"""
# The latest are returned, in chronological order
rows = await self.table.aget_partition(
partition_id=self.session_id,
)
return _rows_to_messages(rows)
[docs]
def add_message(self, message: BaseMessage) -> None:
"""Write a message to the table
Args:
message: A message to write.
"""
this_row_id = uuid.uuid1()
self.table.put(
partition_id=self.session_id,
row_id=this_row_id,
body_blob=json.dumps(message_to_dict(message)),
ttl_seconds=self.ttl_seconds,
)
[docs]
async def aadd_messages(self, messages: Sequence[BaseMessage]) -> None:
for message in messages:
this_row_id = uuid.uuid1()
await self.table.aput(
partition_id=self.session_id,
row_id=this_row_id,
body_blob=json.dumps(message_to_dict(message)),
ttl_seconds=self.ttl_seconds,
)
[docs]
def clear(self) -> None:
"""Clear session memory from DB"""
self.table.delete_partition(self.session_id)
[docs]
async def aclear(self) -> None:
"""Clear session memory from DB"""
await self.table.adelete_partition(self.session_id)
