feat: update ModelExpress metadata API to SourceIdentity-based schema (#21222)

python/sglang/srt/configs/load_config.py

@@ -79,6 +79,12 @@ class LoadConfig:
     remote_instance_weight_loader_transfer_engine: Optional[Any] = None
     modelexpress_url: Optional[str] = None
     modelexpress_model_name: Optional[str] = None
+    # Fields for building SourceIdentity (needed by both seed and client)
+    modelexpress_tp_size: Optional[int] = None
+    modelexpress_pp_size: Optional[int] = None
+    modelexpress_ep_size: Optional[int] = None
+    modelexpress_dtype: Optional[str] = None
+    modelexpress_quantization: Optional[str] = None
 
     # ModelOpt-specific loading options
     modelopt_checkpoint_restore_path: Optional[str] = None

python/sglang/srt/model_executor/model_runner.py

@@ -24,6 +24,7 @@ import os
 import socket
 import threading
 import time
+import uuid
 from collections import defaultdict
 from dataclasses import dataclass
 from typing import Callable, List, Optional, Tuple, Union
@@ -839,6 +840,17 @@ class ModelRunner(ModelRunnerKVCacheMixin):
             )
             return
 
+        # Build SourceIdentity for this instance
+        identity = p2p_pb2.SourceIdentity(
+            model_name=model_name,
+            backend_framework=p2p_pb2.BACKEND_FRAMEWORK_SGLANG,
+            tensor_parallel_size=self.server_args.tp_size,
+            pipeline_parallel_size=self.server_args.pp_size,
+            expert_parallel_size=self.server_args.ep_size,
+            dtype=self.server_args.dtype or "",
+            quantization=self.server_args.quantization or "",
+        )
+
         # Build tensor descriptors from weight_info dict
         tensors = []
         for name, (addr, numel, element_size) in weight_info.items():
@@ -857,27 +869,33 @@ class ModelRunner(ModelRunnerKVCacheMixin):
             tensors=tensors,
         )
 
+        # Generate a unique worker_id for this running instance
+        worker_id = str(uuid.uuid4())
+
         mx_client = MxClient(server_url=mx_url)
         try:
             logger.info(
                 "ModelExpress source: publishing metadata for model=%s, "
-                "tp_rank=%d, session=%s, %d tensors",
+                "tp_rank=%d, session=%s, %d tensors, worker_id=%s",
                 model_name,
                 self.tp_rank,
                 session_id,
                 len(tensors),
+                worker_id,
             )
-            mx_client.publish_metadata(model_name, [worker])
-            mx_client.publish_ready(
-                model_name,
-                worker_id=self.tp_rank,
-                session_id=mx_client.session_id,
-                metadata_hash="",
+            mx_source_id = mx_client.publish_metadata(identity, worker, worker_id)
+            mx_client.update_status(
+                mx_source_id=mx_source_id,
+                worker_id=worker_id,
+                worker_rank=self.tp_rank,
+                status=p2p_pb2.SOURCE_STATUS_READY,
             )
             logger.info(
-                "ModelExpress source: published ready for model=%s, tp_rank=%d",
+                "ModelExpress source: published ready for model=%s, "
+                "tp_rank=%d, mx_source_id=%s",
                 model_name,
                 self.tp_rank,
+                mx_source_id,
             )
         finally:
             mx_client.close()
@@ -1173,6 +1191,11 @@ class ModelRunner(ModelRunnerKVCacheMixin):
             modelexpress_url=self.server_args.modelexpress_url,
             modelexpress_model_name=self.server_args.modelexpress_model_name
             or self.server_args.model_path,
+            modelexpress_tp_size=self.server_args.tp_size,
+            modelexpress_pp_size=self.server_args.pp_size,
+            modelexpress_ep_size=self.server_args.ep_size,
+            modelexpress_dtype=self.server_args.dtype,
+            modelexpress_quantization=self.server_args.quantization or "",
             modelopt_config=modelopt_config,
             rl_quant_profile=self.server_args.rl_quant_profile,
             draft_model_idx=self.draft_model_idx,

python/sglang/srt/model_loader/loader.py

@@ -2289,6 +2289,8 @@ class RemoteInstanceModelLoader(BaseModelLoader):
     ):
         """Load weights via ModelExpress coordination + TransferEngine RDMA."""
         try:
+            import grpc
+            from modelexpress import p2p_pb2
             from modelexpress.client import MxClient
         except ImportError as exc:
             raise ImportError(
@@ -2304,6 +2306,13 @@ class RemoteInstanceModelLoader(BaseModelLoader):
         tp_rank = load_config.tp_rank
         model_name = load_config.modelexpress_model_name
 
+        target_device = torch.device(device_config.device)
+        for _, module in model.named_modules():
+            quant_method = getattr(module, "quant_method", None)
+            if quant_method is not None:
+                with device_loading_context(module, target_device):
+                    quant_method.process_weights_after_loading(module)
+
         logger.info(
             "ModelExpress: registering memory regions for tp_rank=%d...", tp_rank
         )
@@ -2311,39 +2320,63 @@ class RemoteInstanceModelLoader(BaseModelLoader):
             model, transfer_engine
         )
 
-        # Wait for seed to be ready via ModelExpress
+        # Build SourceIdentity matching the seed's identity
+        identity = p2p_pb2.SourceIdentity(
+            model_name=model_name,
+            backend_framework=p2p_pb2.BACKEND_FRAMEWORK_SGLANG,
+            tensor_parallel_size=load_config.modelexpress_tp_size or 1,
+            pipeline_parallel_size=load_config.modelexpress_pp_size or 1,
+            expert_parallel_size=load_config.modelexpress_ep_size or 1,
+            dtype=load_config.modelexpress_dtype or "",
+            quantization=load_config.modelexpress_quantization or "",
+        )
+
+        # Query MX server for a READY source matching our identity and rank
         mx_client = MxClient(server_url=load_config.modelexpress_url)
         try:
             logger.info(
-                "ModelExpress: waiting for seed ready (model=%s)...",
+                "ModelExpress: looking for seed (model=%s, rank=%d)...",
                 model_name,
+                tp_rank,
             )
-            ready, session_id, metadata_hash = mx_client.wait_for_ready(
-                model_name,
-                worker_id=tp_rank,
-            )
-            if not ready:
+            try:
+                resp = mx_client.list_sources(
+                    identity=identity,
+                    status_filter=p2p_pb2.SOURCE_STATUS_READY,
+                )
+            except grpc.RpcError as e:
                 raise RuntimeError(
-                    f"ModelExpress: timed out waiting for seed ready "
-                    f"(model={model_name}, worker={tp_rank})"
+                    f"ModelExpress: cannot reach server at "
+                    f"{load_config.modelexpress_url}: "
+                    f"{e.code()}: {e.details()}"
+                ) from e
+
+            source_ref = None
+            for inst in resp.instances:
+                if inst.worker_rank == tp_rank:
+                    source_ref = inst
+                    break
+
+            if source_ref is None:
+                raise RuntimeError(
+                    f"ModelExpress: no READY source found for "
+                    f"model={model_name}, rank={tp_rank}. "
+                    f"Ensure the seed instance is running and has published metadata."
                 )
 
-            response = mx_client.get_metadata(model_name)
+            # Fetch full metadata for the discovered worker
+            response = mx_client.get_metadata(
+                mx_source_id=source_ref.mx_source_id,
+                worker_id=source_ref.worker_id,
+            )
             if not response.found:
                 raise RuntimeError(
-                    f"ModelExpress: no metadata found for model={model_name}"
+                    f"ModelExpress: no metadata found for "
+                    f"source_id={source_ref.mx_source_id}, "
+                    f"worker_id={source_ref.worker_id}"
                 )
 
-            # Find the worker matching our tp_rank
-            source_worker = None
-            for w in response.workers:
-                if w.worker_rank == tp_rank:
-                    source_worker = w
-                    break
-            if source_worker is None:
-                raise RuntimeError(
-                    f"ModelExpress: no worker metadata for rank={tp_rank}"
-                )
+            source_worker = response.worker
 
             # Extract session_id from oneof backend_metadata
             backend_field = source_worker.WhichOneof("backend_metadata")