🦜️🏓 LangServe¶

pip install "langserve[all]"

langchain app new my-app

add_routes(app. NotImplemented)

poetry add [package-name] // e.g `poetry add langchain-openai`

export OPENAI_API_KEY="sk-..."

poetry run langchain serve --port=8100

#!/usr/bin/env python
from fastapi import FastAPI
from langchain.prompts import ChatPromptTemplate
from langchain.chat_models import ChatAnthropic, ChatOpenAI
from langserve import add_routes

app = FastAPI(
    title="LangChain Server",
    version="1.0",
    description="A simple api server using Langchain's Runnable interfaces",
)

add_routes(
    app,
    ChatOpenAI(),
    path="/openai",
)

add_routes(
    app,
    ChatAnthropic(),
    path="/anthropic",
)

model = ChatAnthropic()

prompt = ChatPromptTemplate.from_template("tell me a joke about {topic}")

add_routes(
    app,
    prompt | model,
    path="/joke",
)

if __name__ == "__main__":
    import uvicorn

    uvicorn.run(app, host="localhost", port=8000)

from fastapi.middleware.cors import CORSMiddleware

# Set all CORS enabled origins
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
    expose_headers=["*"],
)

curl localhost:8000/docs

from langchain.schema import SystemMessage, HumanMessage
from langchain.prompts import ChatPromptTemplate
from langchain.schema.runnable import RunnableMap
from langserve import RemoteRunnable

openai = RemoteRunnable("http://localhost:8000/openai/")
anthropic = RemoteRunnable("http://localhost:8000/anthropic/")
joke_chain = RemoteRunnable("http://localhost:8000/joke/")

joke_chain.invoke({"topic": "parrots"})

# or async
await joke_chain.ainvoke({"topic": "parrots"})

prompt = [
    SystemMessage(content='Act like either a cat or a parrot.'),
    HumanMessage(content='Hello!')
]

# Supports astream
async for msg in anthropic.astream(prompt):
    print(msg, end="", flush=True)

prompt = ChatPromptTemplate.from_messages(
    [("system", "Tell me a long story about {topic}")]
)

# Can define custom chains
chain = prompt | RunnableMap({
    "openai": openai,
    "anthropic": anthropic,
})

chain.batch([{"topic": "parrots"}, {"topic": "cats"}])

import { RemoteRunnable } from "@langchain/core/runnables/remote";

const chain = new RemoteRunnable({
    url: `http://localhost:8000/joke/`,
});
const result = await chain.invoke({
    topic: "cats",
});

import requests

response = requests.post(
    "http://localhost:8000/joke/invoke",
    json={'input': {'topic': 'cats'}}
)
response.json()

curl --location --request POST 'http://localhost:8000/joke/invoke' \
    --header 'Content-Type: application/json' \
    --data-raw '{
        "input": {
            "topic": "cats"
        }
    }'

...
add_routes(
    app,
    runnable,
    path="/my_runnable",
)

# Declare a chain
prompt = ChatPromptTemplate.from_messages(
    [
        ("system", "You are a helpful, professional assistant named Cob."),
        MessagesPlaceholder(variable_name="messages"),
    ]
)

chain = prompt | ChatAnthropic(model="claude-2")


class InputChat(BaseModel):
    """Input for the chat endpoint."""

    messages: List[Union[HumanMessage, AIMessage, SystemMessage]] = Field(
        ...,
        description="The chat messages representing the current conversation.",
    )


add_routes(
    app,
    chain.with_types(input_type=InputChat),
    enable_feedback_endpoint=True,
    enable_public_trace_link_endpoint=True,
    playground_type="chat",
)

from typing import Any

from fastapi import FastAPI
from langchain.schema.runnable import RunnableLambda

app = FastAPI()


def func(x: Any) -> int:
    """Mistyped function that should accept an int but accepts anything."""
    return x + 1


runnable = RunnableLambda(func).with_types(
    input_type=int,
)

add_routes(app, runnable)

from fastapi import FastAPI
from langchain.schema.runnable import RunnableLambda

from langserve import add_routes
from langserve.schema import CustomUserType

app = FastAPI()


class Foo(CustomUserType):
    bar: int


def func(foo: Foo) -> int:
    """Sample function that expects a Foo type which is a pydantic model"""
    assert isinstance(foo, Foo)
    return foo.bar


# Note that the input and output type are automatically inferred!
# You do not need to specify them.
# runnable = RunnableLambda(func).with_types( # <-- Not needed in this case
#     input_type=Foo,
#     output_type=int,
#
add_routes(app, RunnableLambda(func), path="/foo")

type JsonPath = number | string | (number | string)[];
type NameSpacedPath = { title: string; path: JsonPath }; // Using title to mimick json schema, but can use namespace
type OneOfPath = { oneOf: JsonPath[] };

type Widget = {
    type: string // Some well known type (e.g., base64file, chat etc.)
    [key: string]: JsonPath | NameSpacedPath | OneOfPath;
};

try:
    from pydantic.v1 import Field
except ImportError:
    from pydantic import Field

from langserve import CustomUserType


# ATTENTION: Inherit from CustomUserType instead of BaseModel otherwise
#            the server will decode it into a dict instead of a pydantic model.
class FileProcessingRequest(CustomUserType):
    """Request including a base64 encoded file."""

    # The extra field is used to specify a widget for the playground UI.
    file: str = Field(..., extra={"widget": {"type": "base64file"}})
    num_chars: int = 100

class ChatHistory(CustomUserType):
    chat_history: List[Tuple[str, str]] = Field(
        ...,
        examples=[[("human input", "ai response")]],
        extra={"widget": {"type": "chat", "input": "question", "output": "answer"}},
    )
    question: str


def _format_to_messages(input: ChatHistory) -> List[BaseMessage]:
    """Format the input to a list of messages."""
    history = input.chat_history
    user_input = input.question

    messages = []

    for human, ai in history:
        messages.append(HumanMessage(content=human))
        messages.append(AIMessage(content=ai))
    messages.append(HumanMessage(content=user_input))
    return messages


model = ChatOpenAI()
chat_model = RunnableParallel({"answer": (RunnableLambda(_format_to_messages) | model)})
add_routes(
    app,
    chat_model.with_types(input_type=ChatHistory),
    config_keys=["configurable"],
    path="/chat",
)

prompt = ChatPromptTemplate.from_messages(
    [
        ("system", "You are a helpful assisstant named Cob."),
        MessagesPlaceholder(variable_name="messages"),
    ]
)

chain = prompt | ChatAnthropic(model="claude-2")


class MessageListInput(BaseModel):
    """Input for the chat endpoint."""
    messages: List[Union[HumanMessage, AIMessage]] = Field(
        ...,
        description="The chat messages representing the current conversation.",
        extra={"widget": {"type": "chat", "input": "messages"}},
    )


add_routes(
    app,
    chain.with_types(input_type=MessageListInput),
    path="/chat",
)

add_routes(app, chain, enabled_endpoints=["invoke", "batch", "config_hashes"], path="/mychain")

add_routes(app, chain, disabled_endpoints=["playground"], path="/mychain")