From 22cf7d2b42fe34bfb331c8a737715b5ae823df91 Mon Sep 17 00:00:00 2001
From: cctry <shiyang@x.ai>
Date: Tue, 5 May 2026 17:23:42 -0700
Subject: [PATCH] [Fix] Handle nixlRemoteDisconnectError in NixlKVSender
 (#24296)

---
 python/sglang/srt/disaggregation/nixl/conn.py | 71 +++++++++++++++----
 1 file changed, 58 insertions(+), 13 deletions(-)

diff --git a/python/sglang/srt/disaggregation/nixl/conn.py b/python/sglang/srt/disaggregation/nixl/conn.py
index 471ab416f..5c11b3efb 100644
--- a/python/sglang/srt/disaggregation/nixl/conn.py
+++ b/python/sglang/srt/disaggregation/nixl/conn.py
@@ -28,6 +28,21 @@ from sglang.srt.disaggregation.utils import (
 from sglang.srt.environ import envs
 from sglang.srt.server_args import ServerArgs
 
+try:
+    from nixl._bindings import (
+        nixlBackendError,
+        nixlCancelledError,
+        nixlRemoteDisconnectError,
+    )
+
+    _NIXL_TRANSPORT_ERRORS = (
+        nixlRemoteDisconnectError,
+        nixlBackendError,
+        nixlCancelledError,
+    )
+except ImportError:
+    _NIXL_TRANSPORT_ERRORS = (RuntimeError,)
+
 logger = logging.getLogger(__name__)
 
 GUARD = "NixlMsgGuard".encode("ascii")
@@ -1098,6 +1113,8 @@ class NixlKVSender(CommonKVSender):
         self.xfer_handles = []
         self.has_sent = False
         self.chunk_id = 0
+        self._send_failed = False
+        self._send_error: Optional[Exception] = None
 
     def pop_decode_prefix_len(self) -> int:
         return self.kv_mgr.req_to_decode_prefix_len.pop(self.bootstrap_room, 0)
@@ -1110,6 +1127,9 @@ class NixlKVSender(CommonKVSender):
         kv_indices: npt.NDArray[np.int32],
         state_indices: Optional[List[int]] = None,
     ):
+        if self._send_failed:
+            return
+
         index_slice = slice(self.curr_idx, self.curr_idx + len(kv_indices))
         self.curr_idx += len(kv_indices)
         is_last = self.curr_idx == self.num_kv_indices
@@ -1128,15 +1148,24 @@ class NixlKVSender(CommonKVSender):
                 self.kv_mgr.update_status(self.bootstrap_room, KVPoll.Success)
                 return
 
-        new_xfer_handles = self.kv_mgr.add_transfer_request(
-            self.bootstrap_room,
-            kv_indices,
-            index_slice,
-            is_last,
-            self.chunk_id,
-            self.aux_index,
-            state_indices,
-        )
+        try:
+            new_xfer_handles = self.kv_mgr.add_transfer_request(
+                self.bootstrap_room,
+                kv_indices,
+                index_slice,
+                is_last,
+                self.chunk_id,
+                self.aux_index,
+                state_indices,
+            )
+        except _NIXL_TRANSPORT_ERRORS as e:
+            logger.warning(
+                f"KVSender transfer request failed for room {self.bootstrap_room}: {e}"
+            )
+            self._send_failed = True
+            self._send_error = e
+            return
+
         self.xfer_handles.extend(new_xfer_handles)
         self.chunk_id += 1
         if is_last:
@@ -1144,16 +1173,32 @@ class NixlKVSender(CommonKVSender):
             del self.kv_mgr.request_status[self.bootstrap_room]
 
     def poll(self) -> KVPoll:
+        if self._send_failed:
+            return KVPoll.Failed  # type: ignore
         if not self.has_sent:
             return self.kv_mgr.check_status(self.bootstrap_room)
-        states = [self.kv_mgr.agent.check_xfer_state(x) for x in self.xfer_handles]
-        if all([x == "DONE" for x in states]):
+        try:
+            states = [self.kv_mgr.agent.check_xfer_state(x) for x in self.xfer_handles]
+        except _NIXL_TRANSPORT_ERRORS as e:
+            logger.warning(
+                f"KVSender check_xfer_state failed for room {self.bootstrap_room}: {e}"
+            )
+            self._send_failed = True
+            self._send_error = e
+            return KVPoll.Failed  # type: ignore
+        if all(x == "DONE" for x in states):
             return KVPoll.Success  # type: ignore
-        if any([x == "ERR" for x in states]):
-            raise Exception("KVSender transfer encountered an error.")
+        if any(x == "ERR" for x in states):
+            self._send_failed = True
+            self._send_error = RuntimeError(
+                f"NIXL transfer error for room {self.bootstrap_room}"
+            )
+            return KVPoll.Failed  # type: ignore
         return KVPoll.WaitingForInput  # type: ignore
 
     def failure_exception(self):
+        if self._send_error is not None:
+            raise self._send_error
         raise RuntimeError("NIXL KVSender Exception")