75fb9d2fdc
### Overview This PR aims at building on #4378, expanding the capabilities and building on top of the `cassIO` library to interface with the database (as opposed to using the core drivers directly). Usage of `cassIO` (a library abstracting Cassandra access for ML/GenAI-specific purposes) is already established since #6426 was merged, so no new dependencies are introduced. In the same spirit, we try to uniform the interface for using Cassandra instances throughout LangChain: all our appreciation of the work by @jj701 notwithstanding, who paved the way for this incremental work (thank you!), we identified a few reasons for changing the way a `CassandraChatMessageHistory` is instantiated. Advocating a syntax change is something we don't take lighthearted way, so we add some explanations about this below. Additionally, this PR expands on integration testing, enables use of Cassandra's native Time-to-Live (TTL) features and improves the phrasing around the notebook example and the short "integrations" documentation paragraph. We would kindly request @hwchase to review (since this is an elaboration and proposed improvement of #4378 who had the same reviewer). ### About the __init__ breaking changes There are [many](https://docs.datastax.com/en/developer/python-driver/3.28/api/cassandra/cluster/) options when creating the `Cluster` object, and new ones might be added at any time. Choosing some of them and exposing them as `__init__` parameters `CassandraChatMessageHistory` will prove to be insufficient for at least some users. On the other hand, working through `kwargs` or adding a long, long list of arguments to `__init__` is not a desirable option either. For this reason, (as done in #6426), we propose that whoever instantiates the Chat Message History class provide a Cassandra `Session` object, ready to use. This also enables easier injection of mocks and usage of Cassandra-compatible connections (such as those to the cloud database DataStax Astra DB, obtained with a different set of init parameters than `contact_points` and `port`). We feel that a breaking change might still be acceptable since LangChain is at `0.*`. However, while maintaining that the approach we propose will be more flexible in the future, room could be made for a "compatibility layer" that respects the current init method. Honestly, we would to that only if there are strong reasons for it, as that would entail an additional maintenance burden. ### Other changes We propose to remove the keyspace creation from the class code for two reasons: first, production Cassandra instances often employ RBAC so that the database user reading/writing from tables does not necessarily (and generally shouldn't) have permission to create keyspaces, and second that programmatic keyspace creation is not a best practice (it should be done more or less manually, with extra care about schema mismatched among nodes, etc). Removing this (usually unnecessary) operation from the `__init__` path would also improve initialization performance (shorter time). We suggest, likewise, to remove the `__del__` method (which would close the database connection), for the following reason: it is the recommended best practice to create a single Cassandra `Session` object throughout an application (it is a resource-heavy object capable to handle concurrency internally), so in case Cassandra is used in other ways by the app there is the risk of truncating the connection for all usages when the history instance is destroyed. Moreover, the `Session` object, in typical applications, is best left to garbage-collect itself automatically. As mentioned above, we defer the actual database I/O to the `cassIO` library, which is designed to encode practices optimized for LLM applications (among other) without the need to expose LangChain developers to the internals of CQL (Cassandra Query Language). CassIO is already employed by the LangChain's Vector Store support for Cassandra. We added a few more connection options in the companion notebook example (most notably, Astra DB) to encourage usage by anyone who cannot run their own Cassandra cluster. We surface the `ttl_seconds` option for automatic handling of an expiration time to chat history messages, a likely useful feature given that very old messages generally may lose their importance. We elaborated a bit more on the integration testing (Time-to-live, separation of "session ids", ...). ### Remarks from linter & co. We reinstated `cassio` as a dependency both in the "optional" group and in the "integration testing" group of `pyproject.toml`. This might not be the right thing do to, in which case the author of this PR offer his apologies (lack of confidence with Poetry - happy to be pointed in the right direction, though!). During linter tests, we were hit by some errors which appear unrelated to the code in the PR. We left them here and report on them here for awareness: ``` langchain/vectorstores/mongodb_atlas.py:137: error: Argument 1 to "insert_many" of "Collection" has incompatible type "List[Dict[str, Sequence[object]]]"; expected "Iterable[Union[MongoDBDocumentType, RawBSONDocument]]" [arg-type] langchain/vectorstores/mongodb_atlas.py:186: error: Argument 1 to "aggregate" of "Collection" has incompatible type "List[object]"; expected "Sequence[Mapping[str, Any]]" [arg-type] langchain/vectorstores/qdrant.py:16: error: Name "grpc" is not defined [name-defined] langchain/vectorstores/qdrant.py:19: error: Name "grpc" is not defined [name-defined] langchain/vectorstores/qdrant.py:20: error: Name "grpc" is not defined [name-defined] langchain/vectorstores/qdrant.py:22: error: Name "grpc" is not defined [name-defined] langchain/vectorstores/qdrant.py:23: error: Name "grpc" is not defined [name-defined] ``` In the same spirit, we observe that to even get `import langchain` run, it seems that a `pip install bs4` is missing from the minimal package installation path. Thank you! |
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🦜️🔗 LangChain
⚡ Building applications with LLMs through composability ⚡
Looking for the JS/TS version? Check out LangChain.js.
Production Support: As you move your LangChains into production, we'd love to offer more comprehensive support. Please fill out this form and we'll set up a dedicated support Slack channel.
Quick Install
pip install langchain
or
conda install langchain -c conda-forge
🤔 What is this?
Large language models (LLMs) are emerging as a transformative technology, enabling developers to build applications that they previously could not. However, using these LLMs in isolation is often insufficient for creating a truly powerful app - the real power comes when you can combine them with other sources of computation or knowledge.
This library aims to assist in the development of those types of applications. Common examples of these applications include:
❓ Question Answering over specific documents
- Documentation
- End-to-end Example: Question Answering over Notion Database
💬 Chatbots
- Documentation
- End-to-end Example: Chat-LangChain
🤖 Agents
- Documentation
- End-to-end Example: GPT+WolframAlpha
📖 Documentation
Please see here for full documentation on:
- Getting started (installation, setting up the environment, simple examples)
- How-To examples (demos, integrations, helper functions)
- Reference (full API docs)
- Resources (high-level explanation of core concepts)
🚀 What can this help with?
There are six main areas that LangChain is designed to help with. These are, in increasing order of complexity:
📃 LLMs and Prompts:
This includes prompt management, prompt optimization, a generic interface for all LLMs, and common utilities for working with LLMs.
🔗 Chains:
Chains go beyond a single LLM call and involve sequences of calls (whether to an LLM or a different utility). LangChain provides a standard interface for chains, lots of integrations with other tools, and end-to-end chains for common applications.
📚 Data Augmented Generation:
Data Augmented Generation involves specific types of chains that first interact with an external data source to fetch data for use in the generation step. Examples include summarization of long pieces of text and question/answering over specific data sources.
🤖 Agents:
Agents involve an LLM making decisions about which Actions to take, taking that Action, seeing an Observation, and repeating that until done. LangChain provides a standard interface for agents, a selection of agents to choose from, and examples of end-to-end agents.
🧠 Memory:
Memory refers to persisting state between calls of a chain/agent. LangChain provides a standard interface for memory, a collection of memory implementations, and examples of chains/agents that use memory.
🧐 Evaluation:
[BETA] Generative models are notoriously hard to evaluate with traditional metrics. One new way of evaluating them is using language models themselves to do the evaluation. LangChain provides some prompts/chains for assisting in this.
For more information on these concepts, please see our full documentation.
💁 Contributing
As an open-source project in a rapidly developing field, we are extremely open to contributions, whether it be in the form of a new feature, improved infrastructure, or better documentation.
For detailed information on how to contribute, see here.