[Bugfix] Fix `_reqs_to_process` leak on abort (#26012)

Signed-off-by: NickLucche <nlucches@redhat.com>

tests/v1/kv_connector/unit/test_nixl_connector.py

@@ -33,6 +33,7 @@ from vllm.platforms.interface import Platform
 from vllm.sampling_params import SamplingParams
 from vllm.v1.attention.backends.flash_attn import FlashAttentionBackend
 from vllm.v1.outputs import KVConnectorOutput, ModelRunnerOutput
+from vllm.v1.request import RequestStatus
 
 from .utils import create_request, create_scheduler, create_vllm_config
 
@@ -1023,3 +1024,68 @@ def test_shutdown_cleans_up_resources(dist_init):
         assert mock_dereg.call_count == 2
         mock_dereg.assert_any_call("desc1")
         mock_dereg.assert_any_call("desc2")
+
+
+@patch(
+    "vllm.distributed.kv_transfer.kv_connector.v1.nixl_connector.NixlWrapper",
+    FakeNixlWrapper)
+def test_aborted_request_removed_from_worker_in_batch(dist_init):
+    """
+    Create and schedule a request so that P adds it to in-batch tracking via
+    the real scheduler, then simulate an abort (request not in next scheduler
+    iteration) and verify the worker no longer tracks it as in-batch.
+    """
+    vllm_config = create_vllm_config()
+
+    scheduler = create_scheduler(vllm_config)
+    # KVConnector Worker in P
+    connector = NixlConnector(vllm_config, KVConnectorRole.WORKER)
+    connector.connector_worker = FakeNixlConnectorWorker(vllm_config,
+                                                         connector.engine_id,
+                                                         hand_shake_latency=0)
+
+    # Create a request that triggers do_remote_decode so that
+    # the scheduler adds it to reqs_in_batch
+    req = create_request(request_id=1, do_remote_decode=True, max_tokens=1)
+    scheduler.add_request(req)
+
+    # First scheduling pass - examinate build_connector_meta output
+    sched_out = scheduler.schedule()
+    kv_meta = sched_out.kv_connector_metadata
+    assert kv_meta is not None
+    assert isinstance(kv_meta, NixlConnectorMetadata)
+    assert req.request_id in kv_meta.reqs_in_batch
+
+    #### Model Runner start ####
+    # Bind scheduler-produced metadata and start worker processing.
+    connector.bind_connector_metadata(kv_meta)
+
+    dummy_ctx = ForwardContext(
+        no_compile_layers={},
+        attn_metadata={},
+        virtual_engine=0,
+    )
+    connector.start_load_kv(dummy_ctx)
+
+    # Ensure it was tracked by the worker
+    assert req.request_id in connector.connector_worker._reqs_to_process
+
+    #### Model Runner end ####
+
+    # Abort request - request_finished call in connector scheduler
+    scheduler.finish_requests(req.request_id, RequestStatus.FINISHED_ABORTED)
+    # Second scheduling pass - build metadata with aborted request
+    sched_out2 = scheduler.schedule()
+    kv_meta2 = sched_out2.kv_connector_metadata
+    assert kv_meta2 is not None
+    assert isinstance(kv_meta2, NixlConnectorMetadata)
+    assert req.request_id not in kv_meta2.reqs_in_batch
+
+    # Bind empty/abort metadata and run worker step
+    #### Model Runner start ####
+    connector.bind_connector_metadata(kv_meta2)
+    connector.start_load_kv(dummy_ctx)
+
+    # After abort, the worker should not keep tracking it as "in-batch"
+    assert req.request_id not in connector.connector_worker._reqs_to_process
+    #### Model Runner end ####

vllm/distributed/kv_transfer/kv_connector/v1/nixl_connector.py

@@ -113,6 +113,7 @@ class NixlConnectorMetadata(KVConnectorMetadata):
         self.reqs_to_save: dict[ReqId, ReqMeta] = {}
         self.reqs_to_send: dict[ReqId, float] = {}
         self.reqs_in_batch: set[ReqId] = set()
+        self.reqs_not_processed: set[ReqId] = set()
 
     def add_new_req(
         self,
@@ -287,6 +288,9 @@ class NixlConnectorScheduler:
         # Reqs to send and their expiration time
         self._reqs_need_send: dict[ReqId, float] = {}
         self._reqs_in_batch: set[ReqId] = set()
+        # Reqs to remove from processed set because they're not to send after
+        # remote prefill or aborted.
+        self._reqs_not_processed: set[ReqId] = set()
 
     def get_num_new_matched_tokens(
             self, request: "Request",
@@ -401,11 +405,13 @@ class NixlConnectorScheduler:
 
         meta.reqs_to_send = self._reqs_need_send
         meta.reqs_in_batch = self._reqs_in_batch
+        meta.reqs_not_processed = self._reqs_not_processed
 
         # Clear the list once workers start the transfers
         self._reqs_need_recv.clear()
         self._reqs_need_save.clear()
         self._reqs_in_batch = set()
+        self._reqs_not_processed = set()
         self._reqs_need_send = {}
 
         return meta
@@ -439,8 +445,12 @@ class NixlConnectorScheduler:
             params["do_remote_prefill"] = False
             return False, None
 
-        if (not params.get("do_remote_decode")
-                or request.status != RequestStatus.FINISHED_LENGTH_CAPPED):
+        if not params.get("do_remote_decode"):
+            return False, None
+        if request.status != RequestStatus.FINISHED_LENGTH_CAPPED:
+            # Also include the case of a P/D Prefill request with immediate
+            # block free (eg abort). Stop tracking this request.
+            self._reqs_not_processed.add(request.request_id)
             return False, None
 
         # TODO: check whether block_ids actually ever be 0. If not we could
@@ -1234,6 +1244,10 @@ class NixlConnectorWorker:
         for req_id in metadata.reqs_in_batch:
             self._reqs_to_process.add(req_id)
 
+        # Remove all requests that are not to be processed (eg aborted).
+        for req_id in metadata.reqs_not_processed:
+            self._reqs_to_process.discard(req_id)
+
         # Add to requests that are waiting to be read and track expiration.
         for req_id, expiration_time in metadata.reqs_to_send.items():
             if req_id in self._reqs_to_process: