refactor(metrics): extract bucketTimestampMs to utils and add unit tests

Author: pavelzotikov

workers/grouper/src/index.ts

@@ -23,6 +23,7 @@ import TimeMs from '../../../lib/utils/time';
 import DataFilter from './data-filter';
 import RedisHelper from './redisHelper';
 import { computeDelta } from './utils/repetitionDiff';
+import { bucketTimestampMs } from './utils/bucketTimestamp';
 import { rightTrim } from '../../../lib/utils/string';
 import { hasValue } from '../../../lib/utils/hasValue';
 
@@ -325,20 +326,6 @@ export default class GrouperWorker extends Worker {
     return `ts:project-${metricType}:${projectId}:${granularity}`;
   }
 
-  /**
-   * Returns the current time truncated to the start of the given granularity
-   * bucket in milliseconds. All events within the same bucket share one
-   * timestamp so ON_DUPLICATE SUM accumulates them into a single sample.
-   */
-  private bucketTimestampMs(granularity: 'minutely' | 'hourly' | 'daily'): number {
-    const now = Date.now();
-    switch (granularity) {
-      case 'hourly': return now - (now % TimeMs.HOUR);
-      case 'daily':  return now - (now % TimeMs.DAY);
-      default:       return now - (now % TimeMs.MINUTE); // minutely
-    }
-  }
-
   /**
    * Record project metrics to Redis TimeSeries.
    *
@@ -357,9 +344,9 @@ export default class GrouperWorker extends Worker {
     };
 
     const series = [
-      { key: minutelyKey, label: 'minutely', retentionMs: TimeMs.DAY,        timestampMs: this.bucketTimestampMs('minutely') },
-      { key: hourlyKey,   label: 'hourly',   retentionMs: TimeMs.WEEK,       timestampMs: this.bucketTimestampMs('hourly') },
-      { key: dailyKey,    label: 'daily',    retentionMs: 90 * TimeMs.DAY,   timestampMs: this.bucketTimestampMs('daily') },
+      { key: minutelyKey, label: 'minutely', retentionMs: TimeMs.DAY,        timestampMs: bucketTimestampMs('minutely') },
+      { key: hourlyKey,   label: 'hourly',   retentionMs: TimeMs.WEEK,       timestampMs: bucketTimestampMs('hourly') },
+      { key: dailyKey,    label: 'daily',    retentionMs: 90 * TimeMs.DAY,   timestampMs: bucketTimestampMs('daily') },
     ];
 
     for (const { key, label, retentionMs, timestampMs } of series) {

workers/grouper/src/utils/bucketTimestamp.ts

@@ -0,0 +1,17 @@
+import TimeMs from '../../../../lib/utils/time';
+
+/**
+ * Returns the current time truncated to the start of the given granularity
+ * bucket in milliseconds (UTC). All events within the same bucket share one
+ * timestamp so ON_DUPLICATE SUM accumulates them into a single sample.
+ *
+ * @param granularity - time granularity level
+ * @param now - current timestamp in ms, defaults to Date.now()
+ */
+export function bucketTimestampMs(granularity: 'minutely' | 'hourly' | 'daily', now = Date.now()): number {
+  switch (granularity) {
+    case 'hourly': return now - (now % TimeMs.HOUR);
+    case 'daily':  return now - (now % TimeMs.DAY);
+    default:       return now - (now % TimeMs.MINUTE); // minutely
+  }
+}

workers/grouper/tests/bucketTimestamp.test.ts

@@ -0,0 +1,65 @@
+import '../../../env-test';
+import { bucketTimestampMs } from '../src/utils/bucketTimestamp';
+
+describe('bucketTimestampMs', () => {
+  /**
+   * 2026-04-14T15:37:42.500Z
+   * minute start: 2026-04-14T15:37:00.000Z
+   * hour start:   2026-04-14T15:00:00.000Z
+   * day start:    2026-04-14T00:00:00.000Z
+   */
+  const now = new Date('2026-04-14T15:37:42.500Z').getTime();
+
+  it('truncates to the start of the current minute', () => {
+    const expected = new Date('2026-04-14T15:37:00.000Z').getTime();
+
+    expect(bucketTimestampMs('minutely', now)).toBe(expected);
+  });
+
+  it('truncates to the start of the current hour', () => {
+    const expected = new Date('2026-04-14T15:00:00.000Z').getTime();
+
+    expect(bucketTimestampMs('hourly', now)).toBe(expected);
+  });
+
+  it('truncates to the start of the current day (UTC midnight)', () => {
+    const expected = new Date('2026-04-14T00:00:00.000Z').getTime();
+
+    expect(bucketTimestampMs('daily', now)).toBe(expected);
+  });
+
+  it('returns the same value for two calls within the same minute', () => {
+    const t1 = new Date('2026-04-14T15:37:00.000Z').getTime();
+    const t2 = new Date('2026-04-14T15:37:59.999Z').getTime();
+
+    expect(bucketTimestampMs('minutely', t1)).toBe(bucketTimestampMs('minutely', t2));
+  });
+
+  it('returns different values for two calls in different minutes', () => {
+    const t1 = new Date('2026-04-14T15:37:59.999Z').getTime();
+    const t2 = new Date('2026-04-14T15:38:00.000Z').getTime();
+
+    expect(bucketTimestampMs('minutely', t1)).not.toBe(bucketTimestampMs('minutely', t2));
+  });
+
+  it('returns the same value for two calls within the same hour', () => {
+    const t1 = new Date('2026-04-14T15:00:00.000Z').getTime();
+    const t2 = new Date('2026-04-14T15:59:59.999Z').getTime();
+
+    expect(bucketTimestampMs('hourly', t1)).toBe(bucketTimestampMs('hourly', t2));
+  });
+
+  it('returns the same value for two calls within the same day', () => {
+    const t1 = new Date('2026-04-14T00:00:00.000Z').getTime();
+    const t2 = new Date('2026-04-14T23:59:59.999Z').getTime();
+
+    expect(bucketTimestampMs('daily', t1)).toBe(bucketTimestampMs('daily', t2));
+  });
+
+  it('returns different values for two calls on different days', () => {
+    const t1 = new Date('2026-04-14T23:59:59.999Z').getTime();
+    const t2 = new Date('2026-04-15T00:00:00.000Z').getTime();
+
+    expect(bucketTimestampMs('daily', t1)).not.toBe(bucketTimestampMs('daily', t2));
+  });
+});