feat: using histogram metrics (#10695)

src/lib/features/metrics/impact/batch-histogram.ts

@@ -16,6 +16,7 @@ export class BatchHistogram {
     private help: string;
     private registry: Registry;
     public labelNames: string[] = [];
+    public bucketBoundaries: Set<number | '+Inf'> = new Set();
 
     // Store accumulated data for each label combination
     private store: Map<
@@ -63,6 +64,7 @@ export class BatchHistogram {
         for (const bucket of data.buckets) {
             const current = entry.buckets.get(bucket.le) || 0;
             entry.buckets.set(bucket.le, current + bucket.count);
+            this.bucketBoundaries.add(bucket.le);
         }
     }
 
@@ -73,6 +75,7 @@ export class BatchHistogram {
 
     reset(): void {
         this.store.clear();
+        this.bucketBoundaries.clear();
     }
 
     get() {

src/lib/features/metrics/impact/define-impact-metrics.ts

@@ -5,6 +5,8 @@ export const CLIENT_ERROR_COUNT = 'client_error_count';
 export const SERVER_ERROR_COUNT = 'server_error_count';
 export const REQUEST_COUNT = 'request_count';
 export const HEAP_MEMORY_TOTAL = 'heap_memory_total';
+export const REQUEST_TIME_MS = 'request_time_ms';
+export const SCHEDULER_JOB_TIME_SECONDS = 'scheduler_job_time_seconds';
 
 export const defineImpactMetrics = (flagResolver: IFlagResolver) => {
     flagResolver.impactMetrics?.defineCounter(
@@ -27,4 +29,14 @@ export const defineImpactMetrics = (flagResolver: IFlagResolver) => {
         HEAP_MEMORY_TOTAL,
         'Total heap memory used by the application process',
     );
+    flagResolver.impactMetrics?.defineHistogram(
+        REQUEST_TIME_MS,
+        'Request handling time',
+        [10, 25, 50, 100, 200, 500, 1000, 2000, 5000],
+    );
+    flagResolver.impactMetrics?.defineHistogram(
+        SCHEDULER_JOB_TIME_SECONDS,
+        'Job execution time',
+        [1, 2, 3, 4, 5, 7, 10, 15, 20, 30, 45, 60, 120],
+    );
 };

src/lib/features/metrics/impact/metrics-translator.test.ts

@@ -279,4 +279,68 @@ describe('MetricsTranslator', () => {
             'unleash_histogram_histogram_with_labels_count{unleash_origin="sdk",unleash_service="api"} 5',
         );
     });
+
+    it('should handle histogram bucket changes', async () => {
+        const registry = new Registry();
+        const translator = new MetricsTranslator(registry);
+
+        // Initial histogram with 2 buckets
+        const metrics1 = [
+            {
+                name: 'test_histogram',
+                help: 'test histogram',
+                type: 'histogram' as const,
+                samples: [
+                    {
+                        count: 5,
+                        sum: 2.5,
+                        buckets: [
+                            { le: 1, count: 3 },
+                            { le: '+Inf' as const, count: 5 },
+                        ],
+                    },
+                ],
+            },
+        ];
+
+        const result1 = await translator.translateAndSerializeMetrics(metrics1);
+        expect(result1).toContain(
+            'unleash_histogram_test_histogram_bucket{unleash_origin="sdk",le="1"} 3',
+        );
+        expect(result1).toContain(
+            'unleash_histogram_test_histogram_count{unleash_origin="sdk"} 5',
+        );
+
+        // Same histogram with different bucket (0.5 instead of 1)
+        const metrics2 = [
+            {
+                name: 'test_histogram',
+                help: 'test histogram',
+                type: 'histogram' as const,
+                samples: [
+                    {
+                        count: 7,
+                        sum: 3.5,
+                        buckets: [
+                            { le: 0.5, count: 4 }, // Different bucket boundary
+                            { le: '+Inf' as const, count: 7 },
+                        ],
+                    },
+                ],
+            },
+        ];
+
+        const result2 = await translator.translateAndSerializeMetrics(metrics2);
+
+        expect(result2).toContain(
+            'unleash_histogram_test_histogram_bucket{unleash_origin="sdk",le="0.5"} 4',
+        );
+        expect(result2).toContain(
+            'unleash_histogram_test_histogram_count{unleash_origin="sdk"} 7',
+        );
+
+        expect(result2).not.toContain(
+            'unleash_histogram_test_histogram_count{unleash_origin="sdk"} 5',
+        );
+    });
 });

src/lib/features/metrics/impact/metrics-translator.ts

@@ -53,6 +53,25 @@ export class MetricsTranslator {
         );
     }
 
+    private hasNewBuckets(
+        existingHistogram: BatchHistogram,
+        newBuckets: Array<{ le: number | '+Inf'; count: number }>,
+    ): boolean {
+        const existingBoundaries = existingHistogram.bucketBoundaries;
+
+        if (existingBoundaries.size !== newBuckets.length) {
+            return true;
+        }
+
+        for (const bucket of newBuckets) {
+            if (!existingBoundaries.has(bucket.le)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     private transformLabels(
         labels: Record<string, string | number>,
     ): Record<string, string | number> {
@@ -167,7 +186,13 @@ export class MetricsTranslator {
             let histogram: BatchHistogram;
 
             if (existingMetric && existingMetric instanceof BatchHistogram) {
-                if (this.hasNewLabels(existingMetric, labelNames)) {
+                const firstSample = metric.samples[0]; // all samples should have same buckets
+                const needsRecreation =
+                    !firstSample?.buckets ||
+                    this.hasNewLabels(existingMetric, labelNames) ||
+                    this.hasNewBuckets(existingMetric, firstSample.buckets);
+
+                if (needsRecreation) {
                     this.registry.removeSingleMetric(prefixedName);
 
                     histogram = new BatchHistogram({

src/lib/metrics.ts

@@ -41,10 +41,7 @@ import {
 import type { SchedulerService } from './services/index.js';
 import type { IClientMetricsEnv } from './features/metrics/client-metrics/client-metrics-store-v2-type.js';
 import { DbMetricsMonitor } from './metrics-gauge.js';
-import {
+import * as impactMetrics from './features/metrics/impact/define-impact-metrics.js';
-    HEAP_MEMORY_TOTAL,
-    REQUEST_COUNT,
-} from './features/metrics/impact/define-impact-metrics.js';
 
 export function registerPrometheusPostgresMetrics(
     db: Knex,
@@ -798,15 +795,23 @@ export function registerPrometheusMetrics(
                 })
                 .observe(time);
             config.flagResolver.impactMetrics?.incrementCounter(
-                REQUEST_COUNT,
+                impactMetrics.REQUEST_COUNT,
                 1,
                 { flagNames: ['consumptionModel'], context: {} },
             );
+            config.flagResolver.impactMetrics?.observeHistogram(
+                impactMetrics.REQUEST_TIME_MS,
+                time,
+            );
         },
     );
 
     eventBus.on(events.SCHEDULER_JOB_TIME, ({ jobId, time }) => {
         schedulerDuration.labels(jobId).observe(time);
+        config.flagResolver.impactMetrics?.observeHistogram(
+            impactMetrics.SCHEDULER_JOB_TIME_SECONDS,
+            time,
+        );
     });
 
     eventBus.on(events.FUNCTION_TIME, ({ functionName, className, time }) => {
@@ -1152,7 +1157,7 @@ export function registerPrometheusMetrics(
         collectStaticCounters: async () => {
             try {
                 config.flagResolver.impactMetrics?.updateGauge(
-                    HEAP_MEMORY_TOTAL,
+                    impactMetrics.HEAP_MEMORY_TOTAL,
                     process.memoryUsage().heapUsed,
                     { flagNames: ['consumptionModel'], context: {} },
                 );