chore: import upstream snapshot with attribution

python/sglang/srt/observability/func_timer.py

@@ -0,0 +1,101 @@
+# Copyright 2023-2024 SGLang Team
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""
+Records the latency of some functions
+"""
+
+import asyncio
+import time
+from functools import wraps
+from typing import Any, Callable, Optional
+
+from sglang.srt.observability.utils import exponential_buckets
+
+enable_metrics = False
+
+
+def enable_func_timer():
+    # We need to import prometheus_client after setting the env variable `PROMETHEUS_MULTIPROC_DIR`
+    from prometheus_client import Histogram
+
+    global enable_metrics, FUNC_LATENCY
+    enable_metrics = True
+
+    FUNC_LATENCY = Histogram(
+        "sglang:func_latency_seconds",
+        "Function latency in seconds",
+        # captures latency in range [50ms - ~50s]
+        buckets=exponential_buckets(start=0.05, width=1.5, length=18),
+        labelnames=["name"],
+    )
+
+
+FUNC_LATENCY = None
+
+
+def time_func_latency(
+    func: Callable = None, name: Optional[str] = None
+) -> Callable[..., Any]:
+    """
+    A decorator to observe the latency of a function's execution. Supports both sync and async functions.
+
+    NOTE: We use our own implementation of a timer decorator since prometheus_client does not support async
+    context manager yet.
+
+    Overhead: The overhead introduced here in case of an async function could likely be because of `await` introduced
+    which will return in another coroutine object creation and under heavy load could see longer wall time
+    (scheduling delays due to introduction of another awaitable).
+    """
+
+    def measure(func: Callable[..., Any]) -> Callable[..., Any]:
+        nonlocal name
+
+        name = name or func.__name__
+
+        @wraps(func)
+        async def async_wrapper(*args, **kwargs):
+            if not enable_metrics:
+                return await func(*args, **kwargs)
+
+            metric = FUNC_LATENCY
+            start = time.monotonic()
+            ret = func(*args, **kwargs)
+            if isinstance(ret, asyncio.Future) or asyncio.iscoroutine(ret):
+                try:
+                    ret = await ret
+                finally:
+                    metric.labels(name=name).observe(time.monotonic() - start)
+            return ret
+
+        @wraps(func)
+        def sync_wrapper(*args, **kwargs):
+            if not enable_metrics:
+                return func(*args, **kwargs)
+
+            metric = FUNC_LATENCY
+            start = time.monotonic()
+            try:
+                ret = func(*args, **kwargs)
+            finally:
+                metric.labels(name=name).observe(time.monotonic() - start)
+            return ret
+
+        if asyncio.iscoroutinefunction(func):
+            return async_wrapper
+        return sync_wrapper
+
+    if func:
+        return measure(func)
+    else:
+        return measure