[PP Prefill][NIXL] Fix PP mode transfer completion tracking to wait for all ranks (#15027)

python/sglang/srt/disaggregation/nixl/conn.py

@@ -96,23 +96,35 @@ class KVArgsRegisterInfo:
 class TransferStatus:
     """Used by KV Receiver to know when a transfer is done."""
 
-    # KV chunk IDs that have been received.
-    received_kvs: Set[int] = dataclasses.field(default_factory=set)
-    # Number of kv chunks to expect, will know this after last chunk is received.
-    num_kvs_expected: Optional[int] = None
+    # KV chunks received per pp_rank: {pp_rank: set of chunk_ids}
+    received_kvs_per_pp: Dict[int, Set[int]] = dataclasses.field(
+        default_factory=lambda: defaultdict(set)
+    )
+    # Expected chunk count per pp_rank (set when is_last=True): {pp_rank: expected_count}
+    expected_kvs_per_pp: Dict[int, int] = dataclasses.field(default_factory=dict)
+    # Number of PP ranks expected to send data.
+    num_pp_ranks_expected: Optional[int] = None
     # Whether aux data has been received.
     received_aux: bool = False
+    # Mark as failed
+    is_failure: bool = False
 
     def is_done(self):
-        if self.num_kvs_expected is None:
+        if self.is_failure:
+            return True
+        if self.num_pp_ranks_expected is None or not self.received_aux:
             return False
-        # Check for failure state
-        if self.num_kvs_expected == -1:
-            return True  # Failed transfers are considered "done"
-        return self.num_kvs_expected == len(self.received_kvs) and self.received_aux
+        # All PP ranks must have reported their expected count
+        if len(self.expected_kvs_per_pp) < self.num_pp_ranks_expected:
+            return False
+        # Each PP rank must have received all expected chunks
+        for pp_rank, expected in self.expected_kvs_per_pp.items():
+            if len(self.received_kvs_per_pp[pp_rank]) != expected:
+                return False
+        return True
 
     def is_failed(self):
-        return self.num_kvs_expected == -1
+        return self.is_failure
 
 
 class NixlKVManager(CommonKVManager):
@@ -244,8 +256,8 @@ class NixlKVManager(CommonKVManager):
                 room in self.transfer_statuses
                 and not self.transfer_statuses[room].is_done()
             ):
-                # Mark the transfer as failed by setting a special state
-                self.transfer_statuses[room].num_kvs_expected = -1  # Indicates failure
+                # Mark the transfer as failed
+                self.transfer_statuses[room].is_failure = True
                 affected_rooms.append(room)
 
         logger.error(
@@ -573,7 +585,7 @@ class NixlKVManager(CommonKVManager):
             assert len(chunked_dst_kv_indice) == len(kv_indices)
             assert req.agent_name in self.decode_kv_args_table
 
-            notif = "_".join([str(req.room), "kv", str(chunk_id), str(int(is_last))])
+            notif = f"{req.room}_kv_{chunk_id}_{int(is_last)}_{self.kv_args.pp_rank}"
             decode_tp_size = self.decode_kv_args_table[req.agent_name].decode_tp_size
 
             if self.is_mla_backend or (decode_tp_size == self.attn_tp_size):
@@ -627,14 +639,26 @@ class NixlKVManager(CommonKVManager):
             # the message sender. But the bootstrap room alone should be
             # sufficient to map the status.
             for msg in messages:
-                components = msg.decode("ascii").split("_")
+                components = msg.decode("ascii").split("_", 4)
                 room = int(components[0])
                 if components[1] == "kv":
                     chunk_id = int(components[2])
                     is_last = bool(int(components[3]))
-                    self.transfer_statuses[room].received_kvs.add(chunk_id)
+                    pp_rank = int(components[4]) if len(components) > 4 else 0
+                    # Track received chunks per pp_rank
+                    self.transfer_statuses[room].received_kvs_per_pp[pp_rank].add(
+                        chunk_id
+                    )
                     if is_last:
-                        self.transfer_statuses[room].num_kvs_expected = chunk_id + 1
+                        # Record expected chunk count for this pp_rank
+                        self.transfer_statuses[room].expected_kvs_per_pp[pp_rank] = (
+                            chunk_id + 1
+                        )
+                        # Set num_pp_ranks_expected from table (or default to 1)
+                        if self.transfer_statuses[room].num_pp_ranks_expected is None:
+                            self.transfer_statuses[room].num_pp_ranks_expected = (
+                                self.required_prefill_response_num_table.get(room, 1)
+                            )
                 elif components[1] == "aux":
                     self.transfer_statuses[room].received_aux = True