[model gateway][0/N] router EPD support: add encoder grpc server backend support (#16552)

Co-authored-by: Zongyao Chen <ZongYao.Chen@linux.alibaba.com>
Co-authored-by: Zongyao Chen <solar1s@163.com>

python/sglang/srt/entrypoints/grpc_server.py

@@ -162,6 +162,14 @@ class SGLangSchedulerServicer(sglang_scheduler_pb2_grpc.SglangSchedulerServicer)
         self.scheduler_info = scheduler_info
         self.start_time = time.time()
         self.health_servicer = health_servicer
+        self.mm_receiver = None
+        if (
+            self.server_args.language_only
+            and self.server_args.encoder_transfer_backend == "zmq_to_scheduler"
+        ):
+            from sglang.srt.disaggregation import encode_receiver as mm_receiver
+
+            self.mm_receiver = mm_receiver.create_mm_receiver(self.server_args)
 
         # Start the request manager's event loop using auto_create_handle_loop
         self.request_manager.auto_create_handle_loop()
@@ -179,6 +187,7 @@ class SGLangSchedulerServicer(sglang_scheduler_pb2_grpc.SglangSchedulerServicer)
         try:
             # Convert gRPC request to internal format
             tokenized_req = self._convert_generate_request(request)
+            self._handle_epd_disaggregation_encode_request(request, tokenized_req)
 
             # Submit to request manager (automatically handles n>1)
             response_generator = self.request_manager.generate_request(
@@ -248,19 +257,15 @@ class SGLangSchedulerServicer(sglang_scheduler_pb2_grpc.SglangSchedulerServicer)
         logger.info(f"Receive embedding request: {request.request_id}")
 
         try:
-            # Convert request
             tokenized_req = self._convert_embed_request(request)
 
-            # Submit to request manager
             future = await self.request_manager.embedding_request(
                 obj=tokenized_req,
                 request_id=request.request_id,
             )
 
-            # Wait for result
             result = await future
 
-            # Create response
             return sglang_scheduler_pb2.EmbedResponse(
                 request_id=request.request_id,
                 complete=sglang_scheduler_pb2.EmbedComplete(
@@ -536,6 +541,25 @@ class SGLangSchedulerServicer(sglang_scheduler_pb2_grpc.SglangSchedulerServicer)
             aggregate=_compute_aggregate_protobuf(loads),
         )
 
+    def _handle_epd_disaggregation_encode_request(
+        self,
+        grpc_req: sglang_scheduler_pb2.GenerateRequest,
+        tokenized_req: TokenizedGenerateReqInput,
+    ) -> None:
+        if not self.mm_receiver:
+            return
+
+        image_urls = list(grpc_req.mm_inputs.image_urls)
+        if not image_urls:
+            return
+
+        encode_req = self.mm_receiver.build_and_send_encode_request(
+            image_urls=image_urls,
+            rid=grpc_req.request_id,
+        )
+        tokenized_req.need_wait_for_image = bool(encode_req.need_wait_for_image)
+        tokenized_req.num_items_assigned = encode_req.num_items_assigned
+
     # Helper methods for request/response conversion
 
     def _convert_generate_request(