# MomentoChatMessageHistory

> **Class** in `langchain_community`

📖 [View in docs](https://reference.langchain.com/python/langchain-community/chat_message_histories/momento/MomentoChatMessageHistory)

Chat message history cache that uses Momento as a backend.

See https://gomomento.com/

## Signature

```python
MomentoChatMessageHistory(
    self,
    session_id: str,
    cache_client: momento.CacheClient,
    cache_name: str,
    *,
    key_prefix: str = 'message_store:',
    ttl: Optional[timedelta] = None,
    ensure_cache_exists: bool = True,
)
```

## Parameters

| Name | Type | Required | Description |
|------|------|----------|-------------|
| `session_id` | `str` | Yes | The session ID to use for this chat session. |
| `cache_client` | `CacheClient` | Yes | The Momento cache client. |
| `cache_name` | `str` | Yes | The name of the cache to use to store the messages. |
| `key_prefix` | `str` | No | The prefix to apply to the cache key. Defaults to "message_store:". (default: `'message_store:'`) |
| `ttl` | `Optional[timedelta]` | No | The TTL to use for the messages. Defaults to None, ie the default TTL of the cache will be used. (default: `None`) |
| `ensure_cache_exists` | `bool` | No | Create the cache if it doesn't exist. Defaults to True. (default: `True`) |

## Extends

- `BaseChatMessageHistory`

## Constructors

```python
__init__(
    self,
    session_id: str,
    cache_client: momento.CacheClient,
    cache_name: str,
    *,
    key_prefix: str = 'message_store:',
    ttl: Optional[timedelta] = None,
    ensure_cache_exists: bool = True,
)
```

| Name | Type |
|------|------|
| `session_id` | `str` |
| `cache_client` | `momento.CacheClient` |
| `cache_name` | `str` |
| `key_prefix` | `str` |
| `ttl` | `Optional[timedelta]` |
| `ensure_cache_exists` | `bool` |


## Properties

- `key`
- `cache_client`
- `cache_name`
- `ttl`
- `messages`

## Methods

- [`from_client_params()`](https://reference.langchain.com/python/langchain-community/chat_message_histories/momento/MomentoChatMessageHistory/from_client_params)
- [`add_message()`](https://reference.langchain.com/python/langchain-community/chat_message_histories/momento/MomentoChatMessageHistory/add_message)
- [`clear()`](https://reference.langchain.com/python/langchain-community/chat_message_histories/momento/MomentoChatMessageHistory/clear)

---

[View source on GitHub](https://github.com/langchain-ai/langchain-community/blob/4b280287bd55b99b44db2dd849f02d66c89534d5/libs/community/langchain_community/chat_message_histories/momento.py#L39)