[Frontend] Use request id from header (#10968)

Signed-off-by: Joe Runde <Joseph.Runde@ibm.com>

vllm/entrypoints/openai/serving_completion.py

@@ -30,7 +30,7 @@ from vllm.outputs import RequestOutput
 from vllm.sampling_params import BeamSearchParams, SamplingParams
 from vllm.sequence import Logprob
 from vllm.transformers_utils.tokenizer import AnyTokenizer
-from vllm.utils import merge_async_iterators, random_uuid
+from vllm.utils import merge_async_iterators
 
 logger = init_logger(__name__)
 
@@ -86,7 +86,7 @@ class OpenAIServingCompletion(OpenAIServing):
                 "suffix is not currently supported")
 
         model_name = self.base_model_paths[0].name
-        request_id = f"cmpl-{random_uuid()}"
+        request_id = f"cmpl-{self._base_request_id(raw_request)}"
         created_time = int(time.time())
 
         request_metadata = RequestResponseMetadata(request_id=request_id)