[NIXL][Misc] Expose metrics from NIXL for logging to CLI (#25388)

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

requirements/kv_connectors.txt

 lmcache
-nixl >= 0.5.1 # Required for disaggregated prefill
+nixl >= 0.6.0 # Required for disaggregated prefill

tests/v1/kv_connector/unit/test_nixl_connector.py

@@ -57,6 +57,26 @@ def clear_kv_transfer():
         ensure_kv_transfer_shutdown()
 
 
+def get_default_xfer_telemetry(xferDurationS: float = 1,
+                               postDurationS: float = 1,
+                               totalBytes: int = 1,
+                               descCount: int = 1) -> dict:
+
+    class AttributeDict(dict):
+        __slots__ = ()
+        __getattr__ = dict.__getitem__
+        __setattr__ = dict.__setitem__  # type: ignore[assignment]
+
+    # We can't instantiate nixlXferTelemetry because it's read only and
+    # ray env does not have NIXL, so we must fake it
+    return AttributeDict(
+        xferDuration=xferDurationS * 1e6,  # in us
+        postDuration=postDurationS * 1e6,  # in us
+        totalBytes=totalBytes,
+        descCount=descCount,
+    )
+
+
 class FakeNixlWrapper:
     """Mock implementation of NixlWrapper for testing.
 
@@ -132,6 +152,9 @@ class FakeNixlWrapper:
     def transfer(self, handle: int) -> str:
         return "PROC"
 
+    def get_xfer_telemetry(self, handle: int) -> dict:
+        return get_default_xfer_telemetry()
+
     ############################################################
     # Follow are for changing the behavior during testing.
     ############################################################
@@ -169,6 +192,11 @@ nixl_agent = FakeNixlWrapper
         with open(os.path.join(pkg_root, "__init__.py"), "w") as f:
             f.write(stub)
 
+        # Mock nixlXferTelemetry class
+        pkg_root2 = os.path.join(td, "nixl", "_bindings")
+        os.makedirs(pkg_root2, exist_ok=True)
+        with open(os.path.join(pkg_root2, "__init__.py"), "w") as f:
+            f.write("class nixlXferTelemetry: pass")
         # touch parent package
         open(os.path.join(td, "nixl", "__init__.py"), "w").close()
         yield td
@@ -575,7 +603,7 @@ def test_kv_connector_stats(dist_init):
 
     # Verify stats values are recorded
     assert not stats_after_transfer.is_empty()
-    assert stats_after_transfer.data["num_successful_transfers"] == 1
+    assert stats_after_transfer.num_successful_transfers == 1
 
     # Verify stats are reset after retrieval
     stats_after_reset = connector.get_kv_connector_stats()
@@ -599,16 +627,21 @@ def test_kv_connector_stats_aggregation():
 
     # Record different transfers on each worker
     # Worker 1: 2 transfers
-    worker1_stats.record_transfer()
-    worker1_stats.record_transfer()
+    stats = get_default_xfer_telemetry()
+    worker1_stats.record_transfer(stats)
+    worker1_stats.record_transfer(stats)
 
     # Worker 2: 1 transfer
-    worker2_stats.record_transfer()
+    worker2_stats.record_transfer(stats)
 
     # Worker 3: 3 transfers
-    worker3_stats.record_transfer()
-    worker3_stats.record_transfer()
-    worker3_stats.record_transfer()
+    stats = get_default_xfer_telemetry(xferDurationS=2,
+                                       postDurationS=2,
+                                       totalBytes=2,
+                                       descCount=2)
+    worker3_stats.record_transfer(stats)
+    worker3_stats.record_transfer(stats)
+    worker3_stats.record_transfer(stats)
 
     # Create ModelRunnerOutput instances for each worker
     worker_outputs = []
@@ -636,7 +669,12 @@ def test_kv_connector_stats_aggregation():
         aggregated_output.kv_connector_output.kv_connector_stats
     assert isinstance(kv_connector_stats, NixlKVConnectorStats)
     # Number of total transfers across all workers.
-    assert kv_connector_stats.data["num_successful_transfers"] == 6
+    assert kv_connector_stats.num_successful_transfers == 6
+    # Logging proc, call reduce() to get CLI-friendly stats.
+    cli_stats = kv_connector_stats.reduce()
+    assert cli_stats["Avg xfer time (ms)"] == 1500.0
+    assert cli_stats["Avg post time (ms)"] == 1500.0
+    assert cli_stats["Avg number of descriptors"] == 1.5
 
 
 def test_multi_kv_connector_stats_aggregation():
@@ -649,6 +687,7 @@ def test_multi_kv_connector_stats_aggregation():
 
     from dataclasses import dataclass
 
+    # Mock a KVConnectorStats class for testing aggregation over connectors.
     @dataclass
     class FooKVConnectorStats(KVConnectorStats):
 
@@ -676,7 +715,7 @@ def test_multi_kv_connector_stats_aggregation():
         if nixl_count > 0:
             nixl_stats = NixlKVConnectorStats()
             for _ in range(nixl_count):
-                nixl_stats.record_transfer()
+                nixl_stats.record_transfer(get_default_xfer_telemetry())
             data["NixlConnector"] = nixl_stats
         if foo_count > 0:
             foo_stats = FooKVConnectorStats()
@@ -712,8 +751,10 @@ def test_multi_kv_connector_stats_aggregation():
     assert isinstance(kv_connector_stats, MultiKVConnectorStats)
 
     # Validate per-connector totals across workers
-    assert kv_connector_stats["NixlConnector"].data[
-        "num_successful_transfers"] == 5
+    assert isinstance(kv_connector_stats["NixlConnector"],
+                      NixlKVConnectorStats)
+    assert kv_connector_stats["NixlConnector"].num_successful_transfers == 5
+    assert isinstance(kv_connector_stats["FooConnector"], FooKVConnectorStats)
     assert kv_connector_stats["FooConnector"].data["num_foo_transfers"] == 6
 
 
@@ -755,6 +796,8 @@ def test_abort_timeout_on_prefiller(monkeypatch, distributed_executor_backend):
                 "working_dir": working_dir,  # ship fake nixl package
                 "env_vars": {
                     "VLLM_NIXL_ABORT_REQUEST_TIMEOUT": str(timeout),
+                    # TODO: for ray to carry over, remove once we set
+                    "NIXL_TELEMETRY_ENABLE": "1",
                 },
             }
             ray.init(runtime_env=runtime_env)

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

@@ -4,6 +4,7 @@ import contextlib
 import copy
 import logging
 import math
+import os
 import queue
 import threading
 import time
@@ -54,10 +55,12 @@ logger = init_logger(__name__)
 # Lazy import nixl_wrapper to avoid loading nixl_bindings if nixl is not used
 try:
     from nixl._api import nixl_agent as NixlWrapper
+    from nixl._bindings import nixlXferTelemetry
     logger.info("NIXL is available")
 except ImportError:
     logger.warning("NIXL is not available")
     NixlWrapper = None
+    nixlXferTelemetry = None
 
 try:
     from nixl._api import nixl_agent_config
@@ -476,6 +479,9 @@ class NixlConnectorWorker:
         self.nixl_backends = \
             vllm_config.kv_transfer_config.get_from_extra_config(
                 "backends", ["UCX"])
+        # TODO temporary, once nixl allows for telemetry flag in config
+        # (next release), we can remove this env var.
+        os.environ["NIXL_TELEMETRY_ENABLE"] = "1"
         # Agent.
         non_ucx_backends = [b for b in self.nixl_backends if b != "UCX"]
         if nixl_agent_config is None:
@@ -1175,9 +1181,10 @@ class NixlConnectorWorker:
             for handle, _xfer_stime in handles:
                 xfer_state = self.nixl_wrapper.check_xfer_state(handle)
                 if xfer_state == "DONE":
+                    # Get telemetry from NIXL
+                    res = self.nixl_wrapper.get_xfer_telemetry(handle)
+                    self.xfer_stats.record_transfer(res)
                     self.nixl_wrapper.release_xfer_handle(handle)
-                    # TODO (NickLucche) Get from NIXL telemetry once integrated
-                    self.xfer_stats.record_transfer()
                 elif xfer_state == "PROC":
                     in_progress = True
                     continue
@@ -1449,15 +1456,25 @@ class NixlKVConnectorStats(KVConnectorStats):
     """Container for transfer performance metrics"""
 
     def __post_init__(self):
-        if "num_successful_transfers" not in self.data:
-            self.data["num_successful_transfers"] = 0
+        if not self.data:
+            # Empty container init, no data is passed in.
+            self.reset()
 
     def reset(self):
-        self.data = {"num_successful_transfers": 0}
+        # Must be serializable
+        self.data: dict[str, list[float]] = {
+            "transfer_duration": [],
+            "post_duration": [],
+            "bytes_transferred": [],
+            "num_descriptors": [],
+        }
 
-    def record_transfer(self):
-        # TODO: record actual transfer stats when available
-        self.data["num_successful_transfers"] += 1
+    def record_transfer(self, res: nixlXferTelemetry):
+        # Keep metrics units consistent with rest of the code: time us->s
+        self.data["transfer_duration"].append(res.xferDuration / 1e6)
+        self.data["post_duration"].append(res.postDuration / 1e6)
+        self.data["bytes_transferred"].append(res.totalBytes)
+        self.data["num_descriptors"].append(res.descCount)
 
     def clone_and_reset(self) -> "NixlKVConnectorStats":
         old = copy.copy(self)
@@ -1465,16 +1482,55 @@ class NixlKVConnectorStats(KVConnectorStats):
         return old
 
     def is_empty(self) -> bool:
-        return self.data["num_successful_transfers"] == 0
+        return self.num_successful_transfers == 0
 
     def aggregate(self, other: KVConnectorStats) -> KVConnectorStats:
         if not other.is_empty():
-            self.data["num_successful_transfers"] += other.data[
-                "num_successful_transfers"]
+            for k, v in other.data.items():
+                accumulator = self.data[k]
+                assert isinstance(accumulator, list)
+                accumulator.extend(v)
         return self
 
     def reduce(self) -> dict[str, Union[int, float]]:
-        # TODO: reduce stats to a single value, calculate latency/throughput
+        # Compute compact representative stats suitable for CLI logging
+        if self.is_empty():
             return {
-            "num_successful_transfers": self.data["num_successful_transfers"]
+                "Num successful transfers": 0,
+                "Avg xfer time (ms)": 0,
+                "P90 xfer time (ms)": 0,
+                "Avg post time (ms)": 0,
+                "P90 post time (ms)": 0,
+                "Avg MB per transfer": 0,
+                "Throughput (MB/s)": 0,
+                "Avg number of descriptors": 0,
             }
+
+        xfer_time = np.asarray(self.data["transfer_duration"])
+        post_time = np.asarray(self.data["post_duration"])
+        # Convert to MB for CLI logging.
+        mb = np.asarray(self.data["bytes_transferred"]) / 2**20
+        descs = np.asarray(self.data["num_descriptors"], dtype=np.uint32)
+        n = len(descs)
+        assert n == self.num_successful_transfers
+
+        total_mb = mb.sum()
+        avg_mb = total_mb / n
+
+        total_time_seconds = xfer_time.sum()
+        throughput_mb_s = total_mb / total_time_seconds
+
+        return {
+            "Num successful transfers": n,
+            "Avg xfer time (ms)": round(xfer_time.mean() * 1e3, 3),
+            "P90 xfer time (ms)": round(np.percentile(xfer_time, 90) * 1e3, 3),
+            "Avg post time (ms)": round(post_time.mean() * 1e3, 3),
+            "P90 post time (ms)": round(np.percentile(post_time, 90) * 1e3, 3),
+            "Avg MB per transfer": round(avg_mb, 3),
+            "Throughput (MB/s)": round(throughput_mb_s, 3),
+            "Avg number of descriptors": round(descs.mean(), 1),
+        }
+
+    @property
+    def num_successful_transfers(self) -> int:
+        return len(self.data["transfer_duration"])
\ No newline at end of file

vllm/v1/metrics/loggers.py

@@ -62,7 +62,7 @@ class LoggingStatLogger(StatLoggerBase):
         self.prefix_caching_metrics = PrefixCachingMetrics()
         self.spec_decoding_logging = SpecDecodingLogging()
         kv_tranfer_config = self.vllm_config.kv_transfer_config
-        self.kv_transfer_logging = KVConnectorLogging(kv_tranfer_config)
+        self.kv_connector_logging = KVConnectorLogging(kv_tranfer_config)
         self.last_prompt_throughput: float = 0.0
         self.last_generation_throughput: float = 0.0
 
@@ -101,7 +101,7 @@ class LoggingStatLogger(StatLoggerBase):
                 self.spec_decoding_logging.observe(
                     scheduler_stats.spec_decoding_stats)
             if kv_connector_stats := scheduler_stats.kv_connector_stats:
-                self.kv_transfer_logging.observe(kv_connector_stats)
+                self.kv_connector_logging.observe(kv_connector_stats)
             self.last_scheduler_stats = scheduler_stats
 
     def log(self):
@@ -140,7 +140,7 @@ class LoggingStatLogger(StatLoggerBase):
             self.prefix_caching_metrics.hit_rate * 100,
         )
         self.spec_decoding_logging.log(log_fn=log_fn)
-        self.kv_transfer_logging.log(log_fn=log_fn)
+        self.kv_connector_logging.log(log_fn=log_fn)
 
     def log_engine_initialized(self):
         if self.vllm_config.cache_config.num_gpu_blocks: