[observability] add Ray metric backend wrappers (#26252)

Signed-off-by: Dongjun Na <kmu5544616@gmail.com>

python/sglang/test/observability/fake_ray.py

@@ -0,0 +1,142 @@
+# 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.
+# ==============================================================================
+"""Shared test doubles for Ray-backed observability code paths.
+
+These fakes let tests exercise :mod:`sglang.srt.observability.ray_wrappers`,
+and any DI surface that wires through it, without requiring Ray to be
+installed. The module is consumed by:
+
+* ``test/registered/unit/observability/test_ray_wrappers.py`` — wrapper unit
+  tests.
+* ``test/registered/unit/observability/test_stat_loggers_di.py`` — DI
+  integration tests that verify emissions flow through to the metric instance.
+"""
+
+from __future__ import annotations
+
+import importlib
+import sys
+import types
+
+RAY_FAKE_MODULE_NAMES = (
+    "ray",
+    "ray.util",
+    "ray.util.metrics",
+    "ray.serve",
+    "ray.serve.exceptions",
+    "sglang.srt.observability.ray_wrappers",
+)
+
+
+class FakeRayMetric:
+    """Stand-in for ``ray.util.metrics.{Counter,Gauge,Histogram}``.
+
+    Records every ``inc`` / ``set`` / ``observe`` call so tests can assert on
+    the forwarded value and tags dict.
+    """
+
+    def __init__(
+        self,
+        name: str = "",
+        description: str = "",
+        tag_keys: tuple = (),
+        boundaries=None,
+    ):
+        self.name = name
+        self.description = description
+        self._tag_keys = tuple(tag_keys)
+        self.boundaries = list(boundaries) if boundaries is not None else None
+        self.calls = []  # list of (op, value, tags)
+
+    def inc(self, value, tags=None):
+        self.calls.append(("inc", value, dict(tags or {})))
+
+    def set(self, value, tags=None):
+        self.calls.append(("set", value, dict(tags or {})))
+
+    def observe(self, value, tags=None):
+        self.calls.append(("observe", value, dict(tags or {})))
+
+
+class FakeRayServeException(Exception):
+    pass
+
+
+def make_fake_ray_modules(replica_id: str = "test-replica") -> dict:
+    """Build a dict of fake ray modules suitable for ``sys.modules.update``.
+
+    Each call returns fresh module objects so different tests can use
+    different ``replica_id`` values without cross-contamination.
+    """
+    ray_pkg = types.ModuleType("ray")
+    ray_util = types.ModuleType("ray.util")
+    ray_util_metrics = types.ModuleType("ray.util.metrics")
+    ray_util_metrics.Counter = FakeRayMetric
+    ray_util_metrics.Gauge = FakeRayMetric
+    ray_util_metrics.Histogram = FakeRayMetric
+    ray_util_metrics.Metric = FakeRayMetric
+
+    ray_serve = types.ModuleType("ray.serve")
+    ray_serve_exc = types.ModuleType("ray.serve.exceptions")
+    ray_serve_exc.RayServeException = FakeRayServeException
+    ray_serve.exceptions = ray_serve_exc
+
+    class _ReplicaCtx:
+        class _Id:
+            unique_id = replica_id
+
+        replica_id = _Id()
+
+    ray_serve.get_replica_context = lambda: _ReplicaCtx()
+
+    return {
+        "ray": ray_pkg,
+        "ray.util": ray_util,
+        "ray.util.metrics": ray_util_metrics,
+        "ray.serve": ray_serve,
+        "ray.serve.exceptions": ray_serve_exc,
+    }
+
+
+def load_ray_wrappers_with_fake_ray(replica_id: str = "test-replica"):
+    """Inject fake ray modules into ``sys.modules`` and (re)import ``ray_wrappers``."""
+    fake = make_fake_ray_modules(replica_id=replica_id)
+    sys.modules.update(fake)
+    sys.modules.pop("sglang.srt.observability.ray_wrappers", None)
+    return importlib.import_module("sglang.srt.observability.ray_wrappers")
+
+
+def load_ray_wrappers_without_ray():
+    """Make ``import ray`` fail and (re)import ``ray_wrappers`` cleanly."""
+    for name in (
+        "ray",
+        "ray.util",
+        "ray.util.metrics",
+        "ray.serve",
+        "ray.serve.exceptions",
+    ):
+        sys.modules.pop(name, None)
+        sys.modules[name] = None  # type: ignore[assignment]
+    sys.modules.pop("sglang.srt.observability.ray_wrappers", None)
+    return importlib.import_module("sglang.srt.observability.ray_wrappers")
+
+
+def clear_fake_ray_modules() -> None:
+    """Remove the fake ray modules and the cached ray_wrappers import.
+
+    Tests call this from ``tearDown`` so module state does not leak between
+    tests.
+    """
+    for name in RAY_FAKE_MODULE_NAMES:
+        sys.modules.pop(name, None)