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fix: Use per-model tokenizer in KvawareRouter for multi-model setups #1066

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fix: Use per-model tokenizer in KvawareRouter for multi-model setups #1066

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4b6e677
fix: Use per-model tokenizer in KvawareRouter for multi-model setups
Aug 29, 2026
31c0109
fix: Address review feedback — fix tokenize_prompt and model name han…
Aug 29, 2026
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45 changes: 20 additions & 25 deletions src/vllm_router/routers/routing_logic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -326,7 +326,7 @@ def __init__(
self.instance_id_to_ip = {}
self.session_key = session_key
self.hash_ring = HashRing()
self.tokenizer = None
self.tokenizers: Dict[str, AutoTokenizer] = {}

@gemini-code-assist gemini-code-assist Bot Aug 29, 2026

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high

Replacing self.tokenizer with self.tokenizers in KvawareRouter.__init__ will break LoadAwareRouter (which inherits from KvawareRouter). LoadAwareRouter.tokenize_prompt still references self.tokenizer (e.g., if self.tokenizer is None:), which will now raise an AttributeError because self.tokenizer is no longer initialized in KvawareRouter.__init__.

Please update LoadAwareRouter.tokenize_prompt to use self.tokenizers as well, or unify the tokenization logic between the two routers.

self.threshold = kv_aware_threshold

def start_kv_manager(self):
Expand Down Expand Up @@ -388,24 +388,7 @@ async def route_request(
token_ids = None
# Local-first tokenization, fall back to remote "/tokenize" API on failure
# TODO (Yuhan): Handle chat completions
try:
if self.tokenizer is None:
self.tokenizer = AutoTokenizer.from_pretrained(
endpoints[0].model_names[0]
)
token_ids = self.tokenizer.encode(request_json.get("prompt", ""))
except Exception:
# Remote /tokenize fallback (let errors bubble up to keep behavior simple)
remote_url = endpoints[0].url + "/tokenize"
headers = {"Content-Type": "application/json"}
data = {
"model": endpoints[0].model_names[0],
"prompt": request_json.get("prompt", ""),
}
body = requests.post(
remote_url, headers=headers, json=data, timeout=10
).json()
token_ids = body["tokens"]
token_ids = await self.tokenize_prompt(endpoints, request_json)

event_id = "Lookup" + str(uuid.uuid4())
msg = LookupMsg(tokens=token_ids, event_id=event_id)
Expand Down Expand Up @@ -652,17 +635,29 @@ async def tokenize_prompt(
The remote fallback is a blocking HTTP call, so it runs in an
executor rather than on the event loop.
"""
model_name = request_json.get("model", "")
if not model_name:
raise ValueError("Missing 'model' in request body")
# Find the endpoint serving this model
model_endpoint = next(
(ep for ep in endpoints if model_name in ep.model_names),
endpoints[0] if endpoints else None,
)
try:
if self.tokenizer is None:
self.tokenizer = AutoTokenizer.from_pretrained(
endpoints[0].model_names[0]
if model_name not in self.tokenizers:
self.tokenizers[model_name] = AutoTokenizer.from_pretrained(
model_name
)
return self.tokenizer.encode(request_json.get("prompt", ""))
return self.tokenizers[model_name].encode(
request_json.get("prompt", "")
)
except Exception:
remote_url = endpoints[0].url + "/tokenize"
if model_endpoint is None:
raise
remote_url = model_endpoint.url + "/tokenize"
headers = {"Content-Type": "application/json"}
data = {
"model": endpoints[0].model_names[0],
"model": model_name,
"prompt": request_json.get("prompt", ""),
}
loop = asyncio.get_running_loop()
Expand Down
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