[V1] Support DP with Ray (#18779)

vllm/config.py

@@ -1742,6 +1742,8 @@ class ParallelConfig:
     """Port for data parallel messaging."""
     data_parallel_master_port: int = 29500
     """Port of the data parallel master."""
+    data_parallel_backend: str = "mp"
+    """Backend to use for data parallel, either "mp" or "ray"."""
     enable_expert_parallel: bool = False
     """Use expert parallelism instead of tensor parallelism for MoE layers."""
     max_parallel_loading_workers: Optional[int] = None
@@ -1911,6 +1913,10 @@ class ParallelConfig:
                                      "please install Ray with `pip install "
                                      "ray`.") from ray_utils.ray_import_err
                 backend = "ray"
+            elif self.data_parallel_backend == "ray":
+                logger.info("Using ray distributed inference because "
+                            "data_parallel_backend is ray")
+                backend = "ray"
             elif ray_found:
                 if self.placement_group:
                     backend = "ray"