Share some metrics between the Prometheus exporter and the phone home stats (#13671)

synapse/metrics/common_usage_metrics.py

@@ -0,0 +1,79 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C
+#
+# 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.
+from typing import TYPE_CHECKING
+
+import attr
+
+from synapse.metrics.background_process_metrics import run_as_background_process
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+from prometheus_client import Gauge
+
+# Gauge to expose daily active users metrics
+current_dau_gauge = Gauge(
+    "synapse_admin_daily_active_users",
+    "Current daily active users count",
+)
+
+
+@attr.s(auto_attribs=True)
+class CommonUsageMetrics:
+    """Usage metrics shared between the phone home stats and the prometheus exporter."""
+
+    daily_active_users: int
+
+
+class CommonUsageMetricsManager:
+    """Collects common usage metrics."""
+
+    def __init__(self, hs: "HomeServer") -> None:
+        self._store = hs.get_datastores().main
+        self._clock = hs.get_clock()
+
+    async def get_metrics(self) -> CommonUsageMetrics:
+        """Get the CommonUsageMetrics object. If no collection has happened yet, do it
+        before returning the metrics.
+
+        Returns:
+            The CommonUsageMetrics object to read common metrics from.
+        """
+        return await self._collect()
+
+    async def setup(self) -> None:
+        """Keep the gauges for common usage metrics up to date."""
+        await self._update_gauges()
+        self._clock.looping_call(
+            run_as_background_process,
+            5 * 60 * 1000,
+            desc="common_usage_metrics_update_gauges",
+            func=self._update_gauges,
+        )
+
+    async def _collect(self) -> CommonUsageMetrics:
+        """Collect the common metrics and either create the CommonUsageMetrics object to
+        use if it doesn't exist yet, or update it.
+        """
+        dau_count = await self._store.count_daily_users()
+
+        return CommonUsageMetrics(
+            daily_active_users=dau_count,
+        )
+
+    async def _update_gauges(self) -> None:
+        """Update the Prometheus gauges."""
+        metrics = await self._collect()
+
+        current_dau_gauge.set(float(metrics.daily_active_users))