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

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

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: