feat: Trtllm health check payload use bos_token_id (#3145)

Signed-off-by: tzulingk@nvidia.com <tzulingk@nvidia.com>

components/backends/trtllm/src/dynamo/trtllm/health_check.py

@@ -7,8 +7,46 @@ TRT-LLM-specific health check configuration.
 This module defines the default health check payload for TRT-LLM backends.
 """
 
+import logging
+
 from dynamo.health_check import HealthCheckPayload
 
+logger = logging.getLogger(__name__)
+
+
+def _get_bos_token_id_from_tokenizer(tokenizer) -> int:
+    """
+    Extract BOS token ID from the TRT-LLM tokenizer if available.
+
+    Args:
+        tokenizer: TRT-LLM tokenizer object
+
+    Returns:
+        BOS token ID from the tokenizer, or 1 as fallback
+
+    Note:
+        The TransformersTokenizer class wraps a HuggingFace tokenizer.
+        While TransformersTokenizer doesn't expose bos_token_id directly,
+        the wrapped HuggingFace tokenizer (accessible via tokenizer.tokenizer) does.
+    """
+    if tokenizer is None:
+        return 1
+
+    try:
+        if hasattr(tokenizer, "tokenizer"):
+            inner_tokenizer = getattr(tokenizer, "tokenizer")
+            bos_token_id = getattr(inner_tokenizer, "bos_token_id", None)
+            if bos_token_id is not None:
+                logger.info(
+                    f"Using model's BOS token ID for health check: {bos_token_id}"
+                )
+                return int(bos_token_id)
+    except Exception as e:
+        logger.debug(f"Failed to get BOS token from tokenizer: {e}")
+
+    logger.debug("Using default BOS token ID (1) for health check")
+    return 1
+
 
 class TrtllmHealthCheckPayload(HealthCheckPayload):
     """
@@ -17,14 +55,20 @@ class TrtllmHealthCheckPayload(HealthCheckPayload):
     Provides TRT-LLM defaults and inherits environment override support from base class.
     """
 
-    def __init__(self):
+    def __init__(self, tokenizer=None):
         """
         Initialize TRT-LLM health check payload with TRT-LLM-specific defaults.
+
+        Args:
+            tokenizer: Optional TRT-LLM tokenizer to extract BOS token from.
+                       If provided, will attempt to use the model's actual BOS token.
         """
+        bos_token_id = _get_bos_token_id_from_tokenizer(tokenizer)
+
         # Set TensorRT-LLM default payload - minimal request that completes quickly
         # The handler expects token_ids, stop_conditions, and sampling_options
         self.default_payload = {
-            "token_ids": [1],  # Single token for minimal processing
+            "token_ids": [bos_token_id],
             "stop_conditions": {
                 "max_tokens": 1,  # Generate only 1 token
                 "stop": None,

components/backends/trtllm/src/dynamo/trtllm/main.py

@@ -318,7 +318,7 @@ async def init(runtime: DistributedRuntime, config: Config):
             )
 
         # Get health check payload (checks env var and falls back to TensorRT-LLM default)
-        health_check_payload = TrtllmHealthCheckPayload().to_dict()
+        health_check_payload = TrtllmHealthCheckPayload(tokenizer=tokenizer).to_dict()
 
         if config.publish_events_and_metrics and is_first_worker(config):
             # Initialize and pass in the publisher to the request handler to