[Bugfix] Fix port conflict by obtaining a list of open ports upfront (#21894)

Signed-off-by: Ming Yang <minos.future@gmail.com>

vllm/config/parallel.py

@@ -15,7 +15,7 @@ import vllm.envs as envs
 from vllm.config.utils import config
 from vllm.logger import init_logger
 from vllm.platforms import current_platform
-from vllm.utils import cuda_device_count_stateless, get_open_port
+from vllm.utils import cuda_device_count_stateless, get_open_ports_list
 
 if TYPE_CHECKING:
     from ray.runtime_env import RuntimeEnv
@@ -171,6 +171,11 @@ class ParallelConfig:
     rank: int = 0
     """Global rank in distributed setup."""
 
+    _data_parallel_master_port_list: list[int] = field(default_factory=list)
+    """List of open port auto-queried for data parallel messaging.
+    Set to be private as it's not intended to be configured by users.
+    """
+
     @property
     def world_size_across_dp(self) -> int:
         """world_size_across_dp is TPxPPxDP, it is the size of the world
@@ -183,11 +188,15 @@ class ParallelConfig:
         processes that is related to data parallelism,
         e.g. both in the worker and in the engine, which
         can live in different processes. To avoid port conflicts, we
-        increment the port number each time we need to initialize a
+        pop a new port from the prepared port list each time we need to
-        new process group related to data parallelism.
+        initialize a new process group related to data parallelism.
         """
-        answer = self.data_parallel_master_port
+        if self._data_parallel_master_port_list:
-        self.data_parallel_master_port += 1
+            answer = self._data_parallel_master_port_list.pop()
+        else:
+            answer = self.data_parallel_master_port
+            self.data_parallel_master_port += 1
+
         return answer
 
     def stateless_init_dp_group(self) -> ProcessGroup:
@@ -313,7 +322,10 @@ class ParallelConfig:
 
         if self.data_parallel_size > 1 or self.data_parallel_size_local == 0:
             # Data parallel was specified in the engine args.
-            self.data_parallel_master_port = get_open_port()
+            if not self._data_parallel_master_port_list:
+                self._data_parallel_master_port_list = get_open_ports_list(5)
+            self.data_parallel_master_port = \
+                self._data_parallel_master_port_list.pop()
 
             if not (0 <= self.data_parallel_rank < self.data_parallel_size):
                 raise ValueError(

vllm/utils/__init__.py

@@ -940,6 +940,14 @@ def get_open_port() -> int:
     return _get_open_port()
 
 
+def get_open_ports_list(count: int = 5) -> list[int]:
+    """Get a list of open ports."""
+    ports = set()
+    while len(ports) < count:
+        ports.add(get_open_port())
+    return list(ports)
+
+
 def _get_open_port() -> int:
     port = envs.VLLM_PORT
     if port is not None:

vllm/v1/engine/utils.py

@@ -71,7 +71,7 @@ class EngineHandshakeMetadata:
     connect to.
     """
     addresses: EngineZmqAddresses
-    parallel_config: dict[str, Union[int, str]]
+    parallel_config: dict[str, Union[int, str, list[int]]]
 
 
 class CoreEngineProcManager:
@@ -798,6 +798,8 @@ def wait_for_engine_startup(
                         parallel_config.data_parallel_master_ip,
                         "data_parallel_master_port":
                         parallel_config.data_parallel_master_port,
+                        "_data_parallel_master_port_list":
+                        parallel_config._data_parallel_master_port_list,
                         "data_parallel_size":
                         parallel_config.data_parallel_size,
                     }))