local-llm-server/llm_server/llm/vllm/vllm_backend.py

from typing import Tuple, Union

from flask import jsonify
from vllm import SamplingParams

from llm_server import opts
from llm_server.database.database import log_prompt
from llm_server.llm.llm_backend import LLMBackend


class VLLMBackend(LLMBackend):
    _default_params = vars(SamplingParams())

    def handle_response(self, success, request, response_json_body, response_status_code, client_ip, token, prompt: str, elapsed_time, parameters, headers):
        if len(response_json_body.get('text', [])):
            # Does vllm return the prompt and the response together???
            backend_response = response_json_body['text'][0].split(prompt)[1].strip(' ').strip('\n')
        else:
            # Failsafe
            backend_response = ''
        log_prompt(ip=client_ip, token=token, prompt=prompt, response=backend_response, gen_time=elapsed_time, parameters=parameters, headers=headers, backend_response_code=response_status_code, request_url=request.url,
                   response_tokens=response_json_body.get('details', {}).get('generated_tokens'))
        return jsonify({'results': [{'text': backend_response}]}), 200

    def get_parameters(self, parameters) -> Tuple[dict | None, str | None]:
        try:
            # top_k == -1 means disabled
            top_k = parameters.get('top_k', self._default_params['top_k'])
            if top_k <= 0:
                top_k = -1
            sampling_params = SamplingParams(
                temperature=parameters.get('temperature', self._default_params['temperature']),
                top_p=parameters.get('top_p', self._default_params['top_p']),
                top_k=top_k,
                use_beam_search=True if parameters.get('num_beams', 0) > 1 else False,
                stop=parameters.get('stopping_strings', self._default_params['stop']),
                ignore_eos=parameters.get('ban_eos_token', False),
                max_tokens=parameters.get('max_new_tokens', self._default_params['max_tokens'])
            )
        except ValueError as e:
            return None, str(e).strip('.')

        # We use max_new_tokens throughout the server.
        result = vars(sampling_params)
        result['max_new_tokens'] = result.pop('max_tokens')

        return result, None