Support for guided decoding for offline LLM (#6878)

Co-authored-by: Cyrus Leung <cyrus.tl.leung@gmail.com>

vllm/model_executor/guided_decoding/outlines_decoding.py

@@ -10,6 +10,8 @@ from transformers import PreTrainedTokenizerBase
 
 from vllm.entrypoints.openai.protocol import (ChatCompletionRequest,
                                               CompletionRequest)
+from vllm.model_executor.guided_decoding.guided_fields import (
+    GuidedDecodingRequest)
 from vllm.model_executor.guided_decoding.outlines_logits_processors import (
     CFGLogitsProcessor, JSONLogitsProcessor, RegexLogitsProcessor)
 
@@ -77,8 +79,27 @@ async def get_outlines_guided_decoding_logits_processor(
                                       mode, request.guided_whitespace_pattern)
 
 
+def get_local_outlines_guided_decoding_logits_processor(
+    guided_options: GuidedDecodingRequest, tokenizer: PreTrainedTokenizerBase
+) -> Union[JSONLogitsProcessor, RegexLogitsProcessor, CFGLogitsProcessor,
+           None]:
+    """
+    Given an OpenAI-compatible request, check for guided decoding parameters
+    and get the necessary logits processor for the given guide.
+    We cache logit processors by (guide, tokenizer), and on cache hit
+    we make a shallow copy to reuse the same underlying FSM.
+    """
+    guide, mode = _get_guide_and_mode(guided_options)
+    if not guide or not mode:
+        return None
+
+    return _get_logits_processor(guide, tokenizer, mode,
+                                 guided_options.guided_whitespace_pattern)
+
+
 def _get_guide_and_mode(
-    request: Union[CompletionRequest, ChatCompletionRequest]
+    request: Union[CompletionRequest, ChatCompletionRequest,
+                   GuidedDecodingRequest]
 ) -> Union[Tuple[str, GuidedDecodingMode], Tuple[None, None]]:
 
     if request.guided_json:
@@ -102,7 +123,8 @@ def _get_guide_and_mode(
         return choices_regex, GuidedDecodingMode.CHOICE
     elif request.guided_grammar:
         return request.guided_grammar, GuidedDecodingMode.GRAMMAR
-    elif (request.response_format is not None
+    elif (not isinstance(request, GuidedDecodingRequest)
+          and request.response_format is not None
           and request.response_format.type == "json_object"):
         return JSON_GRAMMAR, GuidedDecodingMode.GRAMMAR
     else: