关于LangChain入门,读者可参考文章NLP(五十六)LangChain入门 。
本文将会介绍LangChain中的重连机制,并尝试给出定制化重连方案。
本文以LangChain中的对话功能(ChatOpenAI
)为例。
LangChain中的重连机制
查看LangChain中对话功能(ChatOpenAI
)的重连机制(retry),其源代码如下:
class ChatOpenAI(BaseChatModel):
...
def _create_retry_decorator(self) -> Callable[[Any], Any]:
import openai
min_seconds = 1
max_seconds = 60
# Wait 2^x * 1 second between each retry starting with
# 4 seconds, then up to 10 seconds, then 10 seconds afterwards
return retry(
reraise=True,
stop=stop_after_attempt(self.max_retries),
wait=wait_exponential(multiplier=1, min=min_seconds, max=max_seconds),
retry=(
retry_if_exception_type(openai.error.Timeout)
| retry_if_exception_type(openai.error.APIError)
| retry_if_exception_type(openai.error.APIConnectionError)
| retry_if_exception_type(openai.error.RateLimitError)
| retry_if_exception_type(openai.error.ServiceUnavailableError)
),
before_sleep=before_sleep_log(logger, logging.WARNING),
)
def completion_with_retry(self, **kwargs: Any) -> Any:
"""Use tenacity to retry the completion call."""
retry_decorator = self._create_retry_decorator()
@retry_decorator
def _completion_with_retry(**kwargs: Any) -> Any:
return self.client.create(**kwargs)
return _completion_with_retry(**kwargs)
可以看到,其编码方式为硬编码(hardcore),采用tenacity
模块实现重连机制,对于支持的报错情形,比如openai.error.Timeout, openai.error.APIError
等,会尝试重连,最小等待时间为1s,最大等待时间为60s,每次重连等待时间会乘以2。
简单重连
我们尝试用一个错误的OpenAI key进行对话,代码如下:
from langchain.chat_models import ChatOpenAI
def chat_bot(input_text: str):
llm = ChatOpenAI(temperature=0,
model_name="gpt-3.5-turbo",
openai_api_key="sk-xxx",
max_retries=5)
return llm.predict(input_text)
if __name__ == '__main__':
text = '中国的首都是哪里?'
print(chat_bot(text))
尽管我们在代码中设置了重连最大次数(max_retries
),代码运行时会直接报错,不会重连,原因是LangChain中的对话功能重连机制没有支持openai.error.AuthenticationError
。输出结果如下:
openai.error.AuthenticationError: Incorrect API key provided: sk-xxx. You can find your API key at https://platform.openai.com/account/api-keys.
此时,我们尝试在源代码的基础上做简单的定制,使得其支持openai.error.AuthenticationError
错误类型,代码如下:
# -*- coding: utf-8 -*-
import openai
from typing import Callable, Any
from tenacity import (
before_sleep_log,
retry,
retry_if_exception_type,
stop_after_attempt,
wait_exponential,
)
from langchain.chat_models import ChatOpenAI
import logging
logger = logging.getLogger(__name__)
class MyChatOpenAI(ChatOpenAI):
def _create_retry_decorator(self) -> Callable[[Any], Any]:
min_seconds = 1
max_seconds = 60
# Wait 2^x * 1 second between each retry starting with
# 4 seconds, then up to 10 seconds, then 10 seconds after wards
return retry(
reraise=True,
stop=stop_after_attempt(self.max_retries),
wait=wait_exponential(multiplier=1, min=min_seconds, max=max_seconds),
retry=(
retry_if_exception_type(openai.error.Timeout)
| retry_if_exception_type(openai.error.APIError)
| retry_if_exception_type(openai.error.APIConnectionError)
| retry_if_exception_type(openai.error.RateLimitError)
| retry_if_exception_type(openai.error.ServiceUnavailableError)
# add new error
| retry_if_exception_type(openai.error.AuthenticationError)
),
before_sleep=before_sleep_log(logger, logging.WARNING),
)
def completion_with_retry(self, **kwargs: Any) -> Any:
"""Use tenacity to retry the completion call."""
retry_decorator = self._create_retry_decorator()
@retry_decorator
def _completion_with_retry(**kwargs: Any) -> Any:
return self.client.create(**kwargs)
return _completion_with_retry(**kwargs)
def chat_bot(input_text: str):
llm = MyChatOpenAI(temperature=0,
model_name="gpt-3.5-turbo",
openai_api_key="sk-xxx",
max_retries=5)
return llm.predict(input_text)
if __name__ == '__main__':
text = '中国的首都是哪里?'
print(chat_bot(text))
分析上述代码,我们在继承ChatOpenAI类的基础上重新创建MyChatOpenAI类,在_create_retry_decorator中的重连错误情形中加入了openai.error.AuthenticationError
错误类型,此时代码输出结果如下:
Retrying __main__.MyChatOpenAI.completion_with_retry.<locals>._completion_with_retry in 1.0 seconds as it raised AuthenticationError: Incorrect API key provided: sk-xxx. You can find your API key at https://platform.openai.com/account/api-keys..
Retrying __main__.MyChatOpenAI.completion_with_retry.<locals>._completion_with_retry in 2.0 seconds as it raised AuthenticationError: Incorrect API key provided: sk-xxx. You can find your API key at https://platform.openai.com/account/api-keys..
Retrying __main__.MyChatOpenAI.completion_with_retry.<locals>._completion_with_retry in 4.0 seconds as it raised AuthenticationError: Incorrect API key provided: sk-xxx. You can find your API key at https://platform.openai.com/account/api-keys..
Retrying __main__.MyChatOpenAI.completion_with_retry.<locals>._completion_with_retry in 8.0 seconds as it raised AuthenticationError: Incorrect API key provided: sk-xxx. You can find your API key at https://platform.openai.com/account/api-keys..
Traceback (most recent call last):
......
openai.error.AuthenticationError: Incorrect API key provided: sk-xxx. You can find your API key at https://platform.openai.com/account/api-keys.
从输出结果中,我们可以看到,该代码确实对openai.error.AuthenticationError
错误类型进行了重连,按照源代码的方式进行重连,一共尝试了5次重连,每次重连等待时间是上一次的两倍。
定制化重连
LangChain中的重连机制也支持定制化。
假设我们的使用场景:某个OpenAI key在调用过程中失效了,那么在重连时希望能快速切换至某个能正常使用的OpenAI key,以下为示例代码(仅需要修改completion_with_retry
函数):
def completion_with_retry(self, **kwargs: Any) -> Any:
"""Use tenacity to retry the completion call."""
retry_decorator = self._create_retry_decorator()
@retry_decorator
def _completion_with_retry(**kwargs: Any) -> Any:
# 重连机制定制化(custom retry)
kwargs['api_key'] = 'right openai key'
return self.client.create(**kwargs)
return _completion_with_retry(**kwargs)
此时就能进行正常的对话功能了。
总结
本文介绍了LangChain中的重连机制,并尝试给出定制化重连方案,希望能对读者有所帮助。
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