Add optional OpenTelemetry integration via kaya-otel

Adds an OTEL_ENABLED opt-in that assembles kaya-otel's OTelMixin into
the app, exporting HTTP/WebSocket traces and request metrics to an
OTLP/HTTP collector. Configured through OTEL_SERVICE_NAME,
OTEL_EXPORTER_OTLP_ENDPOINT, OTEL_EXPORTER_OTLP_HEADERS and
OTEL_EXCLUDED_PATHS (defaults to the /api/health probe endpoint).

kaya-otel is an optional 'otel' extra imported lazily, so default
installs and the test suite do not need the OpenTelemetry packages.
The kaya dependencies are bumped to 0.0.4, which kaya-otel requires.

server/README.md

@@ -69,6 +69,11 @@ All configuration comes from environment variables (see `.env.example`):
 | `CORS_ALLOW_CREDENTIALS` | `false` | `1`/`true`/`yes`/`on` allow cookies/credentials on cross-origin requests |
 | `CORS_EXPOSE_HEADERS` | unset | Comma-separated response headers exposed to the browser |
 | `CORS_MAX_AGE` | `600` | Seconds browsers may cache the preflight response |
+| `OTEL_ENABLED` | `false` | `1`/`true`/`yes`/`on` enable OpenTelemetry traces and metrics (requires the `otel` extra, i.e. `pip install tavolo[otel]`) |
+| `OTEL_SERVICE_NAME` | `tavolo` | `service.name` resource attribute of the exported telemetry |
+| `OTEL_EXPORTER_OTLP_ENDPOINT` | unset | Base URL of an OTLP/HTTP collector (e.g. `http://localhost:4318`); unset uses the exporter default |
+| `OTEL_EXPORTER_OTLP_HEADERS` | unset | Comma-separated `key=value` headers sent to the collector (e.g. authentication) |
+| `OTEL_EXCLUDED_PATHS` | `/api/health` | Comma-separated paths excluded from tracing and metrics (exact matches) |
 | `APP_HOST` / `APP_PORT` | `0.0.0.0` / `8080` | Bind address |
 
 ## Logging

server/pyproject.toml

@@ -32,6 +32,9 @@ dev = [
     "mypy",
     "httpx-ws",
 ]
+otel = [
+    "kaya-otel>=0.0.4",
+]
 
 [tool.setuptools.packages.find]
 where = ["src"]

server/requirements.txt

@@ -50,7 +50,7 @@ idna==3.19
     #   httpx
 iso8601==2.1.0
     # via tortoise-orm
-kaya-core==0.0.3
+kaya-core==0.0.4
     # via
     #   kaya-cors
     #   kaya-oidc
@@ -58,20 +58,20 @@ kaya-core==0.0.3
     #   kaya-rsgi
     #   kaya-session
     #   tavolo (pyproject.toml)
-kaya-cors==0.0.3
+kaya-cors==0.0.4
     # via tavolo (pyproject.toml)
-kaya-oidc==0.0.3
+kaya-oidc==0.0.4
     # via tavolo (pyproject.toml)
-kaya-openapi==0.0.3
+kaya-openapi==0.0.4
     # via tavolo (pyproject.toml)
-kaya-rsgi==0.0.3
+kaya-rsgi==0.0.4
     # via tavolo (pyproject.toml)
-kaya-session==0.0.3
+kaya-session==0.0.4
     # via
     #   kaya-oidc
     #   kaya-session-redis
     #   tavolo (pyproject.toml)
-kaya-session-redis==0.0.3
+kaya-session-redis==0.0.4
     # via tavolo (pyproject.toml)
 pwo==0.1.2
     # via

server/src/tavolo/app.py

@@ -12,7 +12,9 @@ Assembles the :class:`~kaya.core.KayaApp` with four mixins:
   ``/api/openapi.json`` and a Swagger UI at ``/api/docs``)
 
 A :class:`~kaya.cors.CorsMixin` is prepended when CORS is configured via the
-``CORS_*`` environment variables (see :mod:`tavolo.config`).
+``CORS_*`` environment variables (see :mod:`tavolo.config`). A
+:class:`~kaya.otel.OTelMixin` (optional ``otel`` extra) is prepended when
+``OTEL_ENABLED`` is set, adding OpenTelemetry traces and metrics.
 
 Live games are kept in :data:`game_store` (Redis when configured, in-memory
 otherwise). Routes and the websocket handlers are registered by importing
@@ -62,6 +64,36 @@ def cors_mixin_from_settings(settings: Settings) -> Optional[CorsMixin]:
     )
 
 
+def otel_mixin_from_settings(settings: Settings) -> Optional[KayaMixin]:
+    """Build a :class:`~kaya.otel.OTelMixin` from the OTEL_* settings.
+
+    Returns ``None`` — telemetry disabled — unless ``OTEL_ENABLED`` is
+    truthy. kaya-otel is an optional dependency (the ``otel`` extra), so it
+    is imported lazily here: default installs and the test suite never need
+    the OpenTelemetry packages.
+    """
+    if not settings.otel_enabled:
+        return None
+    try:
+        from kaya.otel import OTelMixin
+    except ImportError as exc:
+        raise RuntimeError(
+            "OTEL_ENABLED is set but kaya-otel is not installed; "
+            "install tavolo with the 'otel' extra"
+        ) from exc
+    headers = dict(
+        pair.split("=", 1)
+        for pair in (settings.otel_exporter_headers or ())
+        if "=" in pair
+    )
+    return OTelMixin(
+        service_name=settings.otel_service_name,
+        endpoint=settings.otel_exporter_endpoint,
+        headers=headers or None,
+        excluded_paths=settings.otel_excluded_paths,
+    )
+
+
 session_store: SessionStore
 if settings.redis_url is not None:
     # Lazy client: no connection is opened until a session is actually
@@ -105,6 +137,19 @@ tortoise_mixin = TortoiseMixin(
 
 mixins: list[KayaMixin] = [session_mixin, oidc_mixin, tortoise_mixin, openapi_mixin,
                            DeadlineSchedulerMixin(game_store)]
+otel_mixin = otel_mixin_from_settings(settings)
+if otel_mixin is not None:
+    # First in the list: before hooks run in registration order (after hooks
+    # in reverse), so the span covers session loading, OIDC handling and the
+    # handler itself. CORS, when enabled, is still prepended before it so
+    # preflight short-circuits stay untraced.
+    mixins.insert(0, otel_mixin)
+    log.info(
+        "OpenTelemetry enabled: service=%s endpoint=%s",
+        settings.otel_service_name,
+        settings.otel_exporter_endpoint or "(OTLP default)",
+    )
+
 cors_mixin = cors_mixin_from_settings(settings)
 if cors_mixin is not None:
     # First in the list: preflight requests are answered before the session

server/src/tavolo/config.py

@@ -113,6 +113,16 @@ class Settings:
     cors_allow_credentials: bool
     cors_expose_headers: Optional[Tuple[str, ...]]
     cors_max_age: int
+    # OpenTelemetry (kaya-otel's OTelMixin). Disabled unless OTEL_ENABLED is
+    # truthy; the exporter endpoint falls back to the OTLP/HTTP default
+    # (localhost:4318) when OTEL_EXPORTER_OTLP_ENDPOINT is unset.
+    otel_enabled: bool
+    otel_service_name: str
+    otel_exporter_endpoint: Optional[str]
+    otel_exporter_headers: Optional[Tuple[str, ...]]
+    # Paths excluded from tracing and metrics (exact matches). Defaults to
+    # the health endpoint, which k8s probes would otherwise spam.
+    otel_excluded_paths: Tuple[str, ...]
 
     @staticmethod
     def from_env() -> "Settings":
@@ -159,6 +169,14 @@ class Settings:
             cors_allow_credentials=_env_bool("CORS_ALLOW_CREDENTIALS"),
             cors_expose_headers=_env_list("CORS_EXPOSE_HEADERS"),
             cors_max_age=int(_env("CORS_MAX_AGE", "600")),
+            # OpenTelemetry is opt-in: set OTEL_ENABLED=1 to export traces
+            # and metrics via OTLP/HTTP (requires the ``otel`` extra).
+            otel_enabled=_env_bool("OTEL_ENABLED"),
+            otel_service_name=_env("OTEL_SERVICE_NAME", "tavolo"),
+            otel_exporter_endpoint=os.environ.get("OTEL_EXPORTER_OTLP_ENDPOINT") or None,
+            # Comma-separated key=value pairs, e.g. "Authorization=Bearer x".
+            otel_exporter_headers=_env_list("OTEL_EXPORTER_OTLP_HEADERS"),
+            otel_excluded_paths=_env_list("OTEL_EXCLUDED_PATHS") or ("/api/health",),
         )
 
 

server/tests/test_config.py

@@ -130,5 +130,40 @@ class CorsSettingsTests(unittest.TestCase):
         self.assertEqual(3600, settings.cors_max_age)
 
 
+class OTelSettingsTests(unittest.TestCase):
+    def test_otel_disabled_by_default(self):
+        settings = _settings({})
+        self.assertFalse(settings.otel_enabled)
+        self.assertEqual("tavolo", settings.otel_service_name)
+        self.assertIsNone(settings.otel_exporter_endpoint)
+        self.assertIsNone(settings.otel_exporter_headers)
+
+    def test_otel_enabled_parses_boolean(self):
+        for value in ("1", "true", "TRUE", "yes", "on"):
+            self.assertTrue(_settings({"OTEL_ENABLED": value}).otel_enabled)
+        for value in ("0", "false", "no", "off", "anything-else"):
+            self.assertFalse(_settings({"OTEL_ENABLED": value}).otel_enabled)
+
+    def test_otel_settings_are_passed_through(self):
+        settings = _settings({
+            "OTEL_SERVICE_NAME": "cards",
+            "OTEL_EXPORTER_OTLP_ENDPOINT": "http://collector:4318",
+            "OTEL_EXPORTER_OTLP_HEADERS": "Authorization=Bearer t, X-Tenant=one",
+        })
+        self.assertEqual("cards", settings.otel_service_name)
+        self.assertEqual("http://collector:4318", settings.otel_exporter_endpoint)
+        self.assertEqual(
+            ("Authorization=Bearer t", "X-Tenant=one"),
+            settings.otel_exporter_headers,
+        )
+
+    def test_otel_excluded_paths_defaults_to_health_endpoint(self):
+        self.assertEqual(("/api/health",), _settings({}).otel_excluded_paths)
+
+    def test_otel_excluded_paths_parses_comma_separated_list(self):
+        settings = _settings({"OTEL_EXCLUDED_PATHS": "/api/health, /metrics"})
+        self.assertEqual(("/api/health", "/metrics"), settings.otel_excluded_paths)
+
+
 if __name__ == "__main__":
     unittest.main()

server/tests/test_otel.py

@@ -0,0 +1,88 @@
+"""Unit tests for the OpenTelemetry wiring in :mod:`tavolo.app`.
+
+The mixin under test is kaya-otel's :class:`~kaya.otel.OTelMixin`, an
+optional dependency (the ``otel`` extra); these tests only verify that
+:func:`tavolo.app.otel_mixin_from_settings` maps the ``OTEL_*`` settings
+onto mixin construction. The ``kaya.otel`` module is stubbed in
+``sys.modules`` so the suite does not need the extra installed.
+"""
+from __future__ import annotations
+
+import os
+import sys
+import types
+import unittest
+from unittest.mock import patch
+
+from tavolo.app import otel_mixin_from_settings
+from tavolo.config import Settings
+
+
+def _settings(env: dict) -> Settings:
+    with patch.dict(os.environ, env, clear=True):
+        return Settings.from_env()
+
+
+class _StubOTelMixin:
+    def __init__(self, **kwargs):
+        self.kwargs = kwargs
+
+
+def _stub_kaya_otel():
+    """Install a fake ``kaya.otel`` module and return it."""
+    module = types.ModuleType("kaya.otel")
+    module.OTelMixin = _StubOTelMixin  # type: ignore[attr-defined]
+    return patch.dict(sys.modules, {"kaya.otel": module})
+
+
+class OTelMixinFromSettingsTests(unittest.TestCase):
+    def test_disabled_by_default(self):
+        self.assertIsNone(otel_mixin_from_settings(_settings({})))
+
+    def test_enabled_by_otel_enabled(self):
+        with _stub_kaya_otel():
+            mixin = otel_mixin_from_settings(_settings({"OTEL_ENABLED": "1"}))
+        self.assertIsNotNone(mixin)
+
+    def test_settings_are_passed_through(self):
+        with _stub_kaya_otel():
+            mixin = otel_mixin_from_settings(_settings({
+                "OTEL_ENABLED": "true",
+                "OTEL_SERVICE_NAME": "cards",
+                "OTEL_EXPORTER_OTLP_ENDPOINT": "http://collector:4318",
+                "OTEL_EXPORTER_OTLP_HEADERS": "Authorization=Bearer t, X-Tenant=one",
+            }))
+        assert isinstance(mixin, _StubOTelMixin)
+        self.assertEqual({
+            "service_name": "cards",
+            "endpoint": "http://collector:4318",
+            "headers": {"Authorization": "Bearer t", "X-Tenant": "one"},
+            "excluded_paths": ("/api/health",),
+        }, mixin.kwargs)
+
+    def test_defaults_when_only_enabled(self):
+        with _stub_kaya_otel():
+            mixin = otel_mixin_from_settings(_settings({"OTEL_ENABLED": "on"}))
+        assert isinstance(mixin, _StubOTelMixin)
+        self.assertEqual("tavolo", mixin.kwargs["service_name"])
+        self.assertIsNone(mixin.kwargs["endpoint"])
+        self.assertIsNone(mixin.kwargs["headers"])
+        self.assertEqual(("/api/health",), mixin.kwargs["excluded_paths"])
+
+    def test_excluded_paths_are_passed_through(self):
+        with _stub_kaya_otel():
+            mixin = otel_mixin_from_settings(_settings({
+                "OTEL_ENABLED": "1",
+                "OTEL_EXCLUDED_PATHS": "/api/health,/metrics",
+            }))
+        assert isinstance(mixin, _StubOTelMixin)
+        self.assertEqual(("/api/health", "/metrics"), mixin.kwargs["excluded_paths"])
+
+    def test_missing_extra_raises_runtime_error(self):
+        with patch.dict(sys.modules, {"kaya.otel": None}):
+            with self.assertRaises(RuntimeError):
+                otel_mixin_from_settings(_settings({"OTEL_ENABLED": "1"}))
+
+
+if __name__ == "__main__":
+    unittest.main()