[Bugfix] fix --scheduling-policy=priority & n>1 crashes engine (#29764)

Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>
Signed-off-by: Nick Hill <nhill@redhat.com>
Co-authored-by: Nick Hill <nhill@redhat.com>

tests/v1/core/test_priority_scheduler_random.py

@@ -219,7 +219,17 @@ def test_priority_scheduling_blast(
             vllm_config=scheduler.vllm_config,
         )
         scheduler.add_request(req)
-
+    num_initial_requests = 2
+    for _ in range(num_initial_requests):
+        req = _create_random_request(
+            max_tokens_range=(1, max_output_tokens),
+            num_tokens_range=(1, max_input_tokens),
+            arrival_time_range=(0, 0),
+            priority_range=(4, 4),
+            num_mm_item_range=(0, 2),
+            vllm_config=scheduler.vllm_config,
+        )
+        scheduler.add_request(req)
     for _ in range(20000):
         if len(scheduler.waiting) == 0:
             num_new_requests = random.randint(0, 2)

vllm/v1/core/sched/request_queue.py

@@ -137,31 +137,30 @@ class PriorityRequestQueue(RequestQueue):
     """
     A priority queue that supports heap operations.
 
-    Requests with a smaller value of `priority` are processed first.
+    Respects the ordering defined in the Request class, where
+    requests with a smaller value of `priority` are processed first.
     If multiple requests have the same priority, the one with the earlier
     `arrival_time` is processed first.
     """
 
     def __init__(self) -> None:
-        self._heap: list[tuple[int, float, Request]] = []
+        self._heap: list[Request] = []
 
     def add_request(self, request: Request) -> None:
         """Add a request to the queue according to priority policy."""
-        heapq.heappush(self._heap, (request.priority, request.arrival_time, request))
+        heapq.heappush(self._heap, request)
 
     def pop_request(self) -> Request:
         """Pop a request from the queue according to priority policy."""
         if not self._heap:
             raise IndexError("pop from empty heap")
-        _, _, request = heapq.heappop(self._heap)
-        return request
+        return heapq.heappop(self._heap)
 
     def peek_request(self) -> Request:
         """Peek at the next request in the queue without removing it."""
         if not self._heap:
             raise IndexError("peek from empty heap")
-        _, _, request = self._heap[0]
-        return request
+        return self._heap[0]
 
     def prepend_request(self, request: Request) -> None:
         """Add a request to the queue according to priority policy.
@@ -180,15 +179,13 @@ class PriorityRequestQueue(RequestQueue):
 
     def remove_request(self, request: Request) -> None:
         """Remove a specific request from the queue."""
-        self._heap = [(p, t, r) for p, t, r in self._heap if r != request]
+        self._heap.remove(request)
         heapq.heapify(self._heap)
 
     def remove_requests(self, requests: Iterable[Request]) -> None:
         """Remove multiple specific requests from the queue."""
-        requests_to_remove = set(requests)
-        self._heap = [
-            (p, t, r) for p, t, r in self._heap if r not in requests_to_remove
-        ]
+        requests_to_remove = requests if isinstance(requests, set) else set(requests)
+        self._heap = [r for r in self._heap if r not in requests_to_remove]
         heapq.heapify(self._heap)
 
     def __bool__(self) -> bool:
@@ -203,8 +200,7 @@ class PriorityRequestQueue(RequestQueue):
         """Iterate over the queue according to priority policy."""
         heap_copy = self._heap[:]
         while heap_copy:
-            _, _, request = heapq.heappop(heap_copy)
-            yield request
+            yield heapq.heappop(heap_copy)
 
     def __reversed__(self) -> Iterator[Request]:
         """Iterate over the queue in reverse priority order."""

vllm/v1/request.py

@@ -227,6 +227,19 @@ class Request:
         events, self.events = self.events, []
         return events
 
+    def __lt__(self, other: "Request") -> bool:
+        """
+        Compare two requests based on priority, arrival time, and request ID.
+        Used in priority scheduling.
+        """
+        if self.priority != other.priority:
+            return self.priority < other.priority
+        if self.arrival_time != other.arrival_time:
+            return self.arrival_time < other.arrival_time
+        if self.request_id != other.request_id:
+            return self.request_id < other.request_id
+        return id(self) < id(other)
+
 
 class RequestStatus(enum.IntEnum):
     """Status of a request."""