LangServe

pip install "langserve[all]"

from langchain_core.output_parsers import StrOutputParser
from langchain_core.prompts import ChatPromptTemplate
from langchain_ollama import ChatOllama

# Prompt
prompt = ChatPromptTemplate.from_messages([
    ("system", "你是一个翻译助手。请将输入翻译成{language}。"),
    ("human", "{input}")
])

# LLM
llm = ChatOllama(base_url="http://localhost:11434", model="qwen3:14b", reasoning=False)
parser = StrOutputParser()

# 构建 chain 对象
translation_chain = prompt | llm | parser

from fastapi import FastAPI
from langserve import add_routes
from chain import translation_chain

app = FastAPI(
    title="翻译助手",
    version="v1.0",
    description="基于LangChain框架构建的翻译服务"
)

# 直接传 Chain 对象，不要 invoke
add_routes(app, translation_chain, path="/trans")

if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=8000)

INFO:     Started server process [192489]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)

     __          ___      .__   __.   _______      _______. _______ .______     ____    ____  _______
    |  |        /   \     |  \ |  |  /  _____|    /       ||   ____||   _  \    \   \  /   / |   ____|
    |  |       /  ^  \    |   \|  | |  |  __     |   (----`|  |__   |  |_)  |    \   \/   /  |  |__
    |  |      /  /_\  \   |  . `  | |  | |_ |     \   \    |   __|  |      /      \      /   |   __|
    |  `----./  _____  \  |  |\   | |  |__| | .----)   |   |  |____ |  |\  \----.  \    /    |  |____
    |_______/__/     \__\ |__| \__|  \______| |_______/    |_______|| _| `._____|   \__/     |_______|

LANGSERVE: Playground for chain "/translation/" is live at:
LANGSERVE:  │
LANGSERVE:  └──> /translation/playground/
LANGSERVE:
LANGSERVE: See all available routes at /docs/

curl -X 'POST' \
  'http://127.0.0.1:8000/translation/invoke' \
  -H 'accept: application/json' \
  -H 'Content-Type: application/json' \
  -d '{
  "input": {
    "input": "你好",
    "language": "日语"
  },
  "config": {},
  "kwargs": {
    "additionalProp1": {}
  }
}'
{"output":"こんにちは","metadata":{"run_id":"fb6c033b-e597-4d11-82f8-a1721559cb60","feedback_tokens":[]}}

from langserve import RemoteRunnable

client = RemoteRunnable("http://127.0.0.1:8000/translation")
print(client.invoke({"input": "你好", "language": "法语"}))

Bonjour