[CI] Stabilize multinode DP internal LB completion tests

tests/v1/distributed/test_internal_lb_dp.py

@@ -12,7 +12,7 @@
 import pytest_asyncio
 import requests
 
-from tests.utils import RemoteOpenAIServer
+from tests.utils import ROCM_ENV_OVERRIDES, RemoteOpenAIServer
 from tests.v1.utils import check_request_balancing
 from vllm.platforms import current_platform
 
@@ -27,6 +27,84 @@
 NUM_NODES = 2
 
 
+async def _make_completion_request(
+    client: openai.AsyncOpenAI,
+    model_name: str,
+) -> openai.types.Completion:
+    """Make a single completion request and validate the response.
+
+    Uses temperature=1.0 to ensure diverse outputs across concurrent
+    requests for realistic load balancer testing.
+    """
+    completion = await client.completions.create(
+        model=model_name,
+        prompt="Hello, my name is",
+        max_tokens=5,
+        temperature=1.0,
+    )
+
+    assert completion.id is not None, (
+        f"Expected non-None completion id. usage={completion.usage!r}"
+    )
+    assert completion.choices is not None and len(completion.choices) == 1, (
+        f"Expected 1 choice, got "
+        f"{len(completion.choices) if completion.choices else 'None'}"
+    )
+
+    choice = completion.choices[0]
+    # With temperature=1.0, the model may emit a stop token immediately,
+    # producing empty text with finish_reason='stop'. This is valid
+    # model behavior - the test's purpose is load balancing, not output
+    # quality.
+    assert choice.finish_reason in ("length", "stop"), (
+        f"Expected finish_reason 'length' or 'stop', "
+        f"got {choice.finish_reason!r}. text={choice.text!r}"
+    )
+    if choice.finish_reason == "length":
+        assert len(choice.text) >= 1, (
+            f"Expected non-empty text with finish_reason='length', got {choice.text!r}"
+        )
+
+    assert completion.usage.prompt_tokens > 0, (
+        f"Expected positive prompt_tokens, got {completion.usage.prompt_tokens}"
+    )
+    assert completion.usage.total_tokens > 0, (
+        f"Expected positive total_tokens, got {completion.usage.total_tokens}"
+    )
+    return completion
+
+
+async def _run_request_bursts(
+    client: openai.AsyncOpenAI,
+    model_name: str,
+    num_requests: int = 200,
+    num_bursts: int = 2,
+):
+    """Send multiple bursts of completion requests and validate all succeed."""
+    for burst in range(num_bursts):
+        all_tasks = []
+        for _ in range(num_requests):
+            all_tasks.append(
+                asyncio.create_task(_make_completion_request(client, model_name))
+            )
+            await asyncio.sleep(0.01)
+
+        results = await asyncio.gather(*all_tasks, return_exceptions=True)
+        assert len(results) == num_requests, (
+            f"Burst {burst}: expected {num_requests} results, got {len(results)}"
+        )
+
+        for result in results:
+            if isinstance(result, BaseException):
+                raise result
+
+        assert all(completion is not None for completion in results), (
+            f"Burst {burst}: some completions were None"
+        )
+
+        await asyncio.sleep(0.5)
+
+
 class MultinodeInternalLBServerManager:
     """Manages multi-node data parallel vLLM server instances for internal
     load balancer testing using --headless mode."""
@@ -108,6 +186,7 @@ def start_server(sidx: int, r: int, sargs: list[str]):
                         auto_port=False,
                         env_dict={
                             "VLLM_SERVER_DEV_MODE": "1",
+                            **ROCM_ENV_OVERRIDES,
                             current_platform.device_control_env_var: ",".join(
                                 str(current_platform.device_id_to_physical_device_id(i))
                                 for i in range(r, r + gpus_per_node)
@@ -229,6 +308,7 @@ def start_api_server():
                     auto_port=False,
                     env_dict={
                         "VLLM_SERVER_DEV_MODE": "1",
+                        **ROCM_ENV_OVERRIDES,
                         # No GPUs needed for API-only server
                     },
                 )
@@ -249,10 +329,11 @@ def start_engines_server():
                     engines_server_args,
                     auto_port=False,
                     env_dict={
+                        **ROCM_ENV_OVERRIDES,
                         current_platform.device_control_env_var: ",".join(
                             str(current_platform.device_id_to_physical_device_id(i))
                             for i in range(self.dp_size * self.tp_size)
-                        )
+                        ),
                     },
                 )
                 server.__enter__()
@@ -395,58 +476,15 @@ async def test_multinode_dp_completion(
     servers: list[tuple[RemoteOpenAIServer, list[str]]],
     model_name: str,
 ) -> None:
-    async def make_request():
-        completion = await client.completions.create(
-            model=model_name, prompt="Hello, my name is", max_tokens=5, temperature=1.0
-        )
-
-        assert completion.id is not None
-        assert completion.choices is not None and len(completion.choices) == 1
-
-        choice = completion.choices[0]
-        # The exact number of tokens can vary slightly with temperature=1.0,
-        # so we check for a reasonable minimum length.
-        assert len(choice.text) >= 1
-        # Finish reason might not always be 'length' if the model finishes early
-        # or due to other reasons, especially with high temperature.
-        # So, we'll accept 'length' or 'stop'.
-        assert choice.finish_reason in ("length", "stop")
-
-        # Token counts can also vary, so we check they are positive.
-        assert completion.usage.completion_tokens > 0
-        assert completion.usage.prompt_tokens > 0
-        assert completion.usage.total_tokens > 0
-        return completion
-
     # Test single request
-    result = await make_request()
+    result = await _make_completion_request(client, model_name)
     assert result is not None
     print("Multi-node internal LB handled single completion request successfully")
 
     await asyncio.sleep(0.5)
 
-    # Send multiple requests - internal LB should distribute across DP ranks
-    num_requests = 200
-    all_tasks = []
-    for _ in range(num_requests):
-        all_tasks.append(asyncio.create_task(make_request()))
-        await asyncio.sleep(0.01)
-
-    results = await asyncio.gather(*all_tasks)
-    assert len(results) == num_requests
-    assert all(completion is not None for completion in results)
-
-    await asyncio.sleep(0.5)
-
-    # Second burst of requests
-    all_tasks = []
-    for _ in range(num_requests):
-        all_tasks.append(asyncio.create_task(make_request()))
-        await asyncio.sleep(0.01)
-
-    results = await asyncio.gather(*all_tasks)
-    assert len(results) == num_requests
-    assert all(completion is not None for completion in results)
+    # Send multiple bursts - internal LB should distribute across DP ranks
+    await _run_request_bursts(client, model_name)
 
     _, server_args = servers[0]
     api_server_count = (
@@ -570,59 +608,16 @@ async def test_api_only_multinode_dp_completion(
 ) -> None:
     """Test API-only server with all engines on separate headless server."""
 
-    async def make_request():
-        completion = await api_only_client.completions.create(
-            model=model_name, prompt="Hello, my name is", max_tokens=5, temperature=1.0
-        )
-
-        assert completion.id is not None
-        assert completion.choices is not None and len(completion.choices) == 1
-
-        choice = completion.choices[0]
-        # The exact number of tokens can vary slightly with temperature=1.0,
-        # so we check for a reasonable minimum length.
-        assert len(choice.text) >= 1
-        # Finish reason might not always be 'length' if the model finishes
-        # early or due to other reasons, especially with high temperature.
-        # So, we'll accept 'length' or 'stop'.
-        assert choice.finish_reason in ("length", "stop")
-
-        # Token counts can also vary, so we check they are positive.
-        assert completion.usage.completion_tokens > 0
-        assert completion.usage.prompt_tokens > 0
-        assert completion.usage.total_tokens > 0
-        return completion
-
     # Test single request
-    result = await make_request()
+    result = await _make_completion_request(api_only_client, model_name)
     assert result is not None
     print("API-only server handled single completion request successfully")
 
     await asyncio.sleep(0.5)
 
-    # Send multiple requests - should be distributed across engines on
+    # Send multiple bursts - should be distributed across engines on
     # headless server
-    num_requests = 200
-    all_tasks = []
-    for _ in range(num_requests):
-        all_tasks.append(asyncio.create_task(make_request()))
-        await asyncio.sleep(0.01)
-
-    results = await asyncio.gather(*all_tasks)
-    assert len(results) == num_requests
-    assert all(completion is not None for completion in results)
-
-    await asyncio.sleep(0.5)
-
-    # Second burst of requests
-    all_tasks = []
-    for _ in range(num_requests):
-        all_tasks.append(asyncio.create_task(make_request()))
-        await asyncio.sleep(0.01)
-
-    results = await asyncio.gather(*all_tasks)
-    assert len(results) == num_requests
-    assert all(completion is not None for completion in results)
+    await _run_request_bursts(api_only_client, model_name)
 
     api_server, api_server_args = api_only_servers[0]
     api_server_count = (