feat: add query interval metric (fixes #225)

README.rst

@@ -158,6 +158,9 @@ The exporter provides a few builtin metrics which can be useful to track query e
 ``queries{database="db",query="q",status="[success|error|timeout]"}``:
   a counter with number of executed queries, per database, query and status.
 
+``query_interval{query="q"}``:
+  a gauge reporting the configured execution interval in seconds, if set, per query.
+
 ``query_latency{database="db",query="q"}``:
   a histogram with query latencies, per database and query.
 

pyproject.toml

@@ -92,9 +92,6 @@ skip_covered = true
 
 [tool.coverage.run]
 source = [ "query_exporter" ]
-omit = [
-  "query_exporter/main.py",
-]
 
 [tool.mypy]
 ignore_missing_imports = true

query_exporter/main.py

@@ -2,6 +2,7 @@
 
 from functools import partial
 from pathlib import Path
+import typing as t
 
 from aiohttp.web import Application
 import click
@@ -11,6 +12,7 @@
     MetricConfig,
     PrometheusExporterScript,
 )
+from prometheus_client.metrics import Gauge
 
 from . import __version__
 from .config import (
@@ -19,6 +21,7 @@
     load_config,
 )
 from .loop import QueryLoop
+from .metrics import QUERY_INTERVAL_METRIC_NAME
 
 
 class QueryExporterScript(PrometheusExporterScript):
@@ -60,21 +63,26 @@ def configure(self, args: Arguments) -> None:
         if args.check_only:
             raise SystemExit(0)
         self.create_metrics(self.config.metrics.values())
+        self._set_static_metrics()
 
-    async def on_application_startup(self, application: Application) -> None:
+    async def on_application_startup(
+        self, application: Application
+    ) -> None:  # pragma: nocover
         query_loop = QueryLoop(self.config, self.registry, self.logger)
         application["exporter"].set_metric_update_handler(
             partial(self._update_handler, query_loop)
         )
         application["query-loop"] = query_loop
         await query_loop.start()
 
-    async def on_application_shutdown(self, application: Application) -> None:
+    async def on_application_shutdown(
+        self, application: Application
+    ) -> None:  # pragma: nocover
         await application["query-loop"].stop()
 
     async def _update_handler(
         self, query_loop: QueryLoop, metrics: list[MetricConfig]
-    ) -> None:
+    ) -> None:  # pragma: nocover
         """Run queries with no specified schedule on each request."""
         await query_loop.run_aperiodic_queries()
         query_loop.clear_expired_series()
@@ -87,5 +95,15 @@ def _load_config(self, paths: list[Path]) -> Config:
             self.logger.error("invalid config", error=str(error))
             raise SystemExit(1)
 
+    def _set_static_metrics(self) -> None:
+        query_interval_metric = t.cast(
+            Gauge, self.registry.get_metric(QUERY_INTERVAL_METRIC_NAME)
+        )
+        for query in self.config.queries.values():
+            if query.interval:
+                query_interval_metric.labels(query=query.name).set(
+                    query.interval
+                )
+
 
 script = QueryExporterScript()

query_exporter/metrics.py

@@ -34,10 +34,21 @@
     type="histogram",
     labels=("query",),
 )
+# metrics reporting the query interval
+QUERY_INTERVAL_METRIC_NAME = "query_interval"
+_QUERY_INTERVAL_METRIC_CONFIG = MetricConfig(
+    name=QUERY_INTERVAL_METRIC_NAME,
+    description="Query execution interval",
+    type="gauge",
+    labels=("query",),
+)
+
+
 BUILTIN_METRICS = frozenset(
     (
         DB_ERRORS_METRIC_NAME,
         QUERIES_METRIC_NAME,
+        QUERY_INTERVAL_METRIC_NAME,
         QUERY_LATENCY_METRIC_NAME,
         QUERY_TIMESTAMP_METRIC_NAME,
     )
@@ -48,7 +59,7 @@ def get_builtin_metric_configs(
     extra_labels: frozenset[str],
 ) -> dict[str, MetricConfig]:
     """Return configuration for builtin metrics."""
-    return {
+    metric_configs = {
         metric_config.name: MetricConfig(
             metric_config.name,
             metric_config.description,
@@ -63,3 +74,5 @@ def get_builtin_metric_configs(
             _QUERY_TIMESTAMP_METRIC_CONFIG,
         )
     }
+    metric_configs[QUERY_INTERVAL_METRIC_NAME] = _QUERY_INTERVAL_METRIC_CONFIG
+    return metric_configs