fix: metrics for toggle count and version (#565)

lib/db/feature-toggle-store.js

@@ -48,6 +48,14 @@ class FeatureToggleStore {
             .map(this.rowToFeature);
     }
 
+    count() {
+        return this.db
+            .count('*')
+            .from(TABLE)
+            .where({ archived: 0 })
+            .then(res => Number(res[0].count));
+    }
+
     getFeature(name) {
         return this.db
             .first(FEATURE_COLUMNS)

lib/metrics.js

@@ -7,12 +7,15 @@ const {
     FEATURE_ARCHIVED,
     FEATURE_REVIVED,
 } = require('./event-type');
+const { version } = require('./routes/api-def');
+const THREE_HOURS = 3 * 60 * 60 * 1000;
 
 exports.startMonitoring = (
     enable,
     eventBus,
     eventStore,
-    clientMetricsStore
+    clientMetricsStore,
+    featureToggleStore
 ) => {
     if (!enable) {
         return;
@@ -44,6 +47,20 @@ exports.startMonitoring = (
         help: 'Number of times a feature toggle has been used',
         labelNames: ['toggle', 'active', 'appName'],
     });
+    const featureTogglesTotal = new client.Gauge({
+        name: 'feature_toggles_total',
+        help: 'Number of feature toggles',
+        labelNames: ['version'],
+    });
+
+    async function collectFeatureToggleMetrics() {
+        featureTogglesTotal.reset();
+        const togglesCount = await featureToggleStore.count();
+        featureTogglesTotal.labels(version).set(togglesCount);
+    }
+
+    collectFeatureToggleMetrics();
+    setInterval(() => collectFeatureToggleMetrics(), THREE_HOURS);
 
     eventBus.on(events.REQUEST_TIME, ({ path, method, time, statusCode }) => {
         requestDuration.labels(path, method, statusCode).observe(time);

lib/metrics.test.js

@@ -11,7 +11,16 @@ const { startMonitoring } = require('./metrics');
 const { register: prometheusRegister } = require('prom-client');
 
 test.before(() => {
-    startMonitoring(true, eventBus, eventStore, clientMetricsStore);
+    const featureToggleStore = {
+        count: () => 123,
+    };
+    startMonitoring(
+        true,
+        eventBus,
+        eventStore,
+        clientMetricsStore,
+        featureToggleStore
+    );
 });
 
 test('should collect metrics for requests', t => {
@@ -70,3 +79,8 @@ test('should collect metrics for db query timings', t => {
         /db_query_duration_seconds{quantile="0\.99",store="foo",action="bar"} 0.1337/
     );
 });
+
+test('should collect metrics for feature toggle size', t => {
+    const metrics = prometheusRegister.metrics();
+    t.regex(metrics, /feature_toggles_total{version="(.*)"} 123/);
+});

lib/server-impl.js

@@ -33,7 +33,8 @@ async function createApp(options) {
         options.serverMetrics,
         eventBus,
         stores.eventStore,
-        stores.clientMetricsStore
+        stores.clientMetricsStore,
+        stores.featureToggleStore
     );
 
     if (typeof config.eventHook === 'function') {