Astra DB, chat message history (#13836)

This PR adds a chat message history component that uses Astra DB for
persistence through the JSON API.
The `astrapy` package is required for this class to work.

I have added tests and a small notebook, and updated the relevant
references in the other docs pages.

(@rlancemartin this is the counterpart of the Cassandra equivalent class
you so helpfully reviewed back at the end of June)

Thank you!

docs/docs/integrations/memory/astradb_chat_message_history.ipynb

@@ -0,0 +1,147 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "90cd3ded",
+   "metadata": {},
+   "source": [
+    "# Astra DB \n",
+    "\n",
+    "> DataStax [Astra DB](https://docs.datastax.com/en/astra/home/astra.html) is a serverless vector-capable database built on Cassandra and made conveniently available through an easy-to-use JSON API.\n",
+    "\n",
+    "This notebook goes over how to use Astra DB to store chat message history."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "f507f58b-bf22-4a48-8daf-68d869bcd1ba",
+   "metadata": {},
+   "source": [
+    "## Setting up\n",
+    "\n",
+    "To run this notebook you need a running Astra DB. Get the connection secrets on your Astra dashboard:\n",
+    "\n",
+    "- the API Endpoint looks like `https://01234567-89ab-cdef-0123-456789abcdef-us-east1.apps.astra.datastax.com`;\n",
+    "- the Token looks like `AstraCS:6gBhNmsk135...`."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "d7092199",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "!pip install --quiet \"astrapy>=0.6.2\""
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "e3d97b65",
+   "metadata": {},
+   "source": [
+    "### Set up the database connection parameters and secrets"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "id": "163d97f0",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdin",
+     "output_type": "stream",
+     "text": [
+      "ASTRA_DB_API_ENDPOINT =  https://01234567-89ab-cdef-0123-456789abcdef-us-east1.apps.astra.datastax.com\n",
+      "ASTRA_DB_APPLICATION_TOKEN =  ········\n"
+     ]
+    }
+   ],
+   "source": [
+    "import getpass\n",
+    "\n",
+    "ASTRA_DB_API_ENDPOINT = input(\"ASTRA_DB_API_ENDPOINT = \")\n",
+    "ASTRA_DB_APPLICATION_TOKEN = getpass.getpass(\"ASTRA_DB_APPLICATION_TOKEN = \")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "55860b2d",
+   "metadata": {},
+   "source": [
+    "Depending on whether local or cloud-based Astra DB, create the corresponding database connection \"Session\" object."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "36c163e8",
+   "metadata": {},
+   "source": [
+    "## Example"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "id": "d15e3302",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from langchain.memory import AstraDBChatMessageHistory\n",
+    "\n",
+    "message_history = AstraDBChatMessageHistory(\n",
+    "    session_id=\"test-session\",\n",
+    "    api_endpoint=ASTRA_DB_API_ENDPOINT,\n",
+    "    token=ASTRA_DB_APPLICATION_TOKEN,\n",
+    ")\n",
+    "\n",
+    "message_history.add_user_message(\"hi!\")\n",
+    "\n",
+    "message_history.add_ai_message(\"whats up?\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "id": "64fc465e",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[HumanMessage(content='hi!'), AIMessage(content='whats up?')]"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "message_history.messages"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.10.12"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

docs/docs/integrations/providers/astradb.mdx

@@ -30,6 +30,20 @@ vector_store = AstraDB(
 Learn more in the [example notebook](/docs/integrations/vectorstores/astradb).
 
 
+### Memory
+
+```python
+from langchain.memory import AstraDBChatMessageHistory
+message_history = AstraDBChatMessageHistory(
+    session_id="test-session"
+    api_endpoint="...",
+    token="...",
+)
+```
+
+Learn more in the [example notebook](/docs/integrations/memory/astradb_chat_message_history).
+
+
 ## Apache Cassandra and Astra DB through CQL
 
 > [Cassandra](https://cassandra.apache.org/) is a NoSQL, row-oriented, highly scalable and highly available database.

libs/langchain/langchain/memory/__init__.py

@@ -32,6 +32,7 @@
 )
 from langchain.memory.buffer_window import ConversationBufferWindowMemory
 from langchain.memory.chat_message_histories import (
+    AstraDBChatMessageHistory,
     CassandraChatMessageHistory,
     ChatMessageHistory,
     CosmosDBChatMessageHistory,
@@ -68,6 +69,7 @@
 from langchain.memory.zep_memory import ZepMemory
 
 __all__ = [
+    "AstraDBChatMessageHistory",
     "CassandraChatMessageHistory",
     "ChatMessageHistory",
     "CombinedMemory",

libs/langchain/langchain/memory/chat_message_histories/__init__.py

@@ -1,3 +1,6 @@
+from langchain.memory.chat_message_histories.astradb import (
+    AstraDBChatMessageHistory,
+)
 from langchain.memory.chat_message_histories.cassandra import (
     CassandraChatMessageHistory,
 )
@@ -31,6 +34,7 @@
 from langchain.memory.chat_message_histories.zep import ZepChatMessageHistory
 
 __all__ = [
+    "AstraDBChatMessageHistory",
     "ChatMessageHistory",
     "CassandraChatMessageHistory",
     "CosmosDBChatMessageHistory",

libs/langchain/langchain/memory/chat_message_histories/astradb.py

@@ -0,0 +1,114 @@
+"""Astra DB - based chat message history, based on astrapy."""
+from __future__ import annotations
+
+import json
+import time
+import typing
+from typing import List, Optional
+
+if typing.TYPE_CHECKING:
+    from astrapy.db import AstraDB as LibAstraDB
+
+from langchain_core.chat_history import BaseChatMessageHistory
+from langchain_core.messages import (
+    BaseMessage,
+    message_to_dict,
+    messages_from_dict,
+)
+
+DEFAULT_COLLECTION_NAME = "langchain_message_store"
+
+
+class AstraDBChatMessageHistory(BaseChatMessageHistory):
+    """Chat message history that stores history in Astra DB.
+
+    Args (only keyword-arguments accepted):
+        session_id: arbitrary key that is used to store the messages
+            of a single chat session.
+        collection_name (str): name of the Astra DB collection to create/use.
+        token (Optional[str]): API token for Astra DB usage.
+        api_endpoint (Optional[str]): full URL to the API endpoint,
+            such as "https://<DB-ID>-us-east1.apps.astra.datastax.com".
+        astra_db_client (Optional[Any]): *alternative to token+api_endpoint*,
+            you can pass an already-created 'astrapy.db.AstraDB' instance.
+        namespace (Optional[str]): namespace (aka keyspace) where the
+            collection is created. Defaults to the database's "default namespace".
+    """
+
+    def __init__(
+        self,
+        *,
+        session_id: str,
+        collection_name: str = DEFAULT_COLLECTION_NAME,
+        token: Optional[str] = None,
+        api_endpoint: Optional[str] = None,
+        astra_db_client: Optional[LibAstraDB] = None,  # type 'astrapy.db.AstraDB'
+        namespace: Optional[str] = None,
+    ) -> None:
+        """Create an Astra DB chat message history."""
+        try:
+            from astrapy.db import AstraDB as LibAstraDB
+        except (ImportError, ModuleNotFoundError):
+            raise ImportError(
+                "Could not import a recent astrapy python package. "
+                "Please install it with `pip install --upgrade astrapy`."
+            )
+
+        # Conflicting-arg checks:
+        if astra_db_client is not None:
+            if token is not None or api_endpoint is not None:
+                raise ValueError(
+                    "You cannot pass 'astra_db_client' to AstraDB if passing "
+                    "'token' and 'api_endpoint'."
+                )
+
+        self.session_id = session_id
+        self.collection_name = collection_name
+        self.token = token
+        self.api_endpoint = api_endpoint
+        self.namespace = namespace
+        if astra_db_client is not None:
+            self.astra_db = astra_db_client
+        else:
+            self.astra_db = LibAstraDB(
+                token=self.token,
+                api_endpoint=self.api_endpoint,
+                namespace=self.namespace,
+            )
+        self.collection = self.astra_db.create_collection(self.collection_name)
+
+    @property
+    def messages(self) -> List[BaseMessage]:  # type: ignore
+        """Retrieve all session messages from DB"""
+        message_blobs = [
+            doc["body_blob"]
+            for doc in sorted(
+                self.collection.paginated_find(
+                    filter={
+                        "session_id": self.session_id,
+                    },
+                    projection={
+                        "timestamp": 1,
+                        "body_blob": 1,
+                    },
+                ),
+                key=lambda _doc: _doc["timestamp"],
+            )
+        ]
+        items = [json.loads(message_blob) for message_blob in message_blobs]
+        messages = messages_from_dict(items)
+        return messages
+
+    def add_message(self, message: BaseMessage) -> None:
+        """Write a message to the table"""
+        self.collection.insert_one(
+            {
+                "timestamp": time.time(),
+                "session_id": self.session_id,
+                "body_blob": json.dumps(message_to_dict(message)),
+            }
+        )
+
+    def clear(self) -> None:
+        """Clear session memory from DB"""
+        self.collection.delete_many(filter={"session_id": self.session_id})