[BugFix] Fix P/D with non-MoE DP (#33037)

Signed-off-by: Nick Hill <nickhill123@gmail.com>

vllm/v1/engine/core.py

@@ -911,6 +911,17 @@ class EngineCoreProc(EngineCore):
                 set_process_title("EngineCore")
             decorate_logs()
 
+            if data_parallel and vllm_config.kv_transfer_config is not None:
+                # modify the engine_id and append the local_dp_rank to it to ensure
+                # that the kv_transfer_config is unique for each DP rank.
+                vllm_config.kv_transfer_config.engine_id = (
+                    f"{vllm_config.kv_transfer_config.engine_id}_dp{local_dp_rank}"
+                )
+                logger.debug(
+                    "Setting kv_transfer_config.engine_id to %s",
+                    vllm_config.kv_transfer_config.engine_id,
+                )
+
             parallel_config.data_parallel_index = dp_rank
             if data_parallel and vllm_config.model_config.is_moe:
                 # Set data parallel rank for this engine process.
@@ -1285,17 +1296,6 @@ class DPEngineCoreProc(EngineCoreProc):
         assert local_dp_rank is not None
         assert 0 <= local_dp_rank <= dp_rank < dp_size
 
-        if vllm_config.kv_transfer_config is not None:
-            # modify the engine_id and append the local_dp_rank to it to ensure
-            # that the kv_transfer_config is unique for each DP rank.
-            vllm_config.kv_transfer_config.engine_id = (
-                f"{vllm_config.kv_transfer_config.engine_id}_dp{local_dp_rank}"
-            )
-            logger.debug(
-                "Setting kv_transfer_config.engine_id to %s",
-                vllm_config.kv_transfer_config.engine_id,
-            )
-
         self.dp_rank = dp_rank
         self.dp_group = vllm_config.parallel_config.stateless_init_dp_group()
 

vllm/v1/engine/utils.py

@@ -313,6 +313,13 @@ class CoreEngineActorManager:
             dp_vllm_config.parallel_config.placement_group = pg
             local_client = index < local_engine_count
 
+            if dp_size > 1 and dp_vllm_config.kv_transfer_config is not None:
+                # modify the engine_id and append the local_dp_rank to it to ensure
+                # that the kv_transfer_config is unique for each DP rank.
+                dp_vllm_config.kv_transfer_config.engine_id = (
+                    f"{dp_vllm_config.kv_transfer_config.engine_id}_dp{local_index}"
+                )
+
             # Ray XPU known issue: dpctl initializes the GPU runtime early, so
             # setting device env vars in Ray actor's initialization method
             # will not affect device selection. See: