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from typing import Any, Dict, List, Union, Optional
import time
import queue
from langchain.callbacks.base import BaseCallbackHandler
from langchain.schema import LLMResult
class StreamingGradioCallbackHandler(BaseCallbackHandler):
"""
Similar to H2OTextIteratorStreamer that is for HF backend, but here LangChain backend
"""
def __init__(self, timeout: Optional[float] = None, block=True):
super().__init__()
self.text_queue = queue.SimpleQueue()
self.stop_signal = None
self.do_stop = False
self.timeout = timeout
self.block = block
def on_llm_start(
self, serialized: Dict[str, Any], prompts: List[str], **kwargs: Any
) -> None:
"""Run when LLM starts running. Clean the queue."""
while not self.text_queue.empty():
try:
self.text_queue.get(block=False)
except queue.Empty:
continue
def on_llm_new_token(self, token: str, **kwargs: Any) -> None:
"""Run on new LLM token. Only available when streaming is enabled."""
self.text_queue.put(token)
def on_llm_end(self, response: LLMResult, **kwargs: Any) -> None:
"""Run when LLM ends running."""
self.text_queue.put(self.stop_signal)
def on_llm_error(
self, error: Union[Exception, KeyboardInterrupt], **kwargs: Any
) -> None:
"""Run when LLM errors."""
self.text_queue.put(self.stop_signal)
def __iter__(self):
return self
def __next__(self):
while True:
try:
value = self.stop_signal # value looks unused in pycharm, not true
if self.do_stop:
print("hit stop", flush=True)
# could raise or break, maybe best to raise and make parent see if any exception in thread
raise StopIteration()
# break
value = self.text_queue.get(block=self.block, timeout=self.timeout)
break
except queue.Empty:
time.sleep(0.01)
if value == self.stop_signal:
raise StopIteration()
else:
return value
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