Loki: Fix metric time splitting to split starting with the start time (#80085)

* Loki: Fix metric time splitting to split starting with the start time

* add test case to gdev-dashboard

* fix splitting test

public/app/plugins/datasource/loki/metricTimeSplitting.test.ts

@@ -1,15 +1,55 @@
 import { splitTimeRange } from './metricTimeSplitting';
 
 describe('metric splitTimeRange', () => {
-  it('should split time range into chunks', () => {
+  it('should split time range into chunks with 1day split and duration', () => {
-    const start = Date.parse('2022-02-06T14:10:03');
+    const start = Date.parse('2022-02-06T14:10:03Z');
-    const end = Date.parse('2022-02-06T14:11:03');
+    const end = Date.parse('2022-02-08T14:11:03Z');
-    const step = 10 * 1000;
+    const step = 24 * 60 * 60 * 1000; // 1 day
+    const rangeDuration = 24 * 60 * 60 * 1000; // 1 day
 
-    expect(splitTimeRange(start, end, step, 25000)).toStrictEqual([
+    expect(splitTimeRange(start, end, step, rangeDuration)).toStrictEqual([
-      [Date.parse('2022-02-06T14:10:00'), Date.parse('2022-02-06T14:10:10')],
+      [Date.parse('2022-02-06T00:00:00Z'), Date.parse('2022-02-06T00:00:00Z')],
-      [Date.parse('2022-02-06T14:10:20'), Date.parse('2022-02-06T14:10:40')],
+      [Date.parse('2022-02-07T00:00:00Z'), Date.parse('2022-02-07T00:00:00Z')],
-      [Date.parse('2022-02-06T14:10:50'), Date.parse('2022-02-06T14:11:10')],
+      [Date.parse('2022-02-08T00:00:00Z'), Date.parse('2022-02-08T00:00:00Z')],
+    ]);
+  });
+
+  it('should split time range into chunks with 1day split and duration and a 5 minute duration', () => {
+    const start = Date.parse('2022-02-06T14:00:00Z');
+    const end = Date.parse('2022-02-06T14:05:00Z');
+    const step = 24 * 60 * 60 * 1000; // 1 day
+    const rangeDuration = 24 * 60 * 60 * 1000; // 1 day
+
+    expect(splitTimeRange(start, end, step, rangeDuration)).toStrictEqual([
+      [Date.parse('2022-02-06T00:00:00Z'), Date.parse('2022-02-06T00:00:00Z')],
+    ]);
+  });
+
+  it('should split time range into chunks with 1hour split and 1day duration', () => {
+    const start = Date.parse('2022-02-06T14:10:03Z');
+    const end = Date.parse('2022-02-08T14:11:03Z');
+    const step = 60 * 60 * 1000; // 1 hour
+    const rangeDuration = 24 * 60 * 60 * 1000; // 1 day
+
+    expect(splitTimeRange(start, end, step, rangeDuration)).toStrictEqual([
+      [Date.parse('2022-02-06T14:00:00Z'), Date.parse('2022-02-07T13:00:00Z')],
+      [Date.parse('2022-02-07T14:00:00Z'), Date.parse('2022-02-08T13:00:00Z')],
+      [Date.parse('2022-02-08T14:00:00Z'), Date.parse('2022-02-08T14:11:03Z')],
+    ]);
+  });
+
+  it('should split time range into chunks with 1hour split and 12h duration', () => {
+    const start = Date.parse('2022-02-06T14:10:03Z');
+    const end = Date.parse('2022-02-08T14:11:03Z');
+    const step = 60 * 60 * 1000; // 1 hour
+    const rangeDuration = 12 * 60 * 60 * 1000; // 12h
+
+    expect(splitTimeRange(start, end, step, rangeDuration)).toStrictEqual([
+      [Date.parse('2022-02-06T14:00:00Z'), Date.parse('2022-02-07T01:00:00Z')],
+      [Date.parse('2022-02-07T02:00:00Z'), Date.parse('2022-02-07T13:00:00Z')],
+      [Date.parse('2022-02-07T14:00:00Z'), Date.parse('2022-02-08T01:00:00Z')],
+      [Date.parse('2022-02-08T02:00:00Z'), Date.parse('2022-02-08T13:00:00Z')],
+      [Date.parse('2022-02-08T14:00:00Z'), Date.parse('2022-02-08T14:11:03Z')],
     ]);
   });
 

public/app/plugins/datasource/loki/metricTimeSplitting.ts

@@ -5,20 +5,6 @@
 // we are trying to be compatible with
 // https://github.com/grafana/loki/blob/089ec1b05f5ec15a8851d0e8230153e0eeb4dcec/pkg/querier/queryrange/split_by_interval.go#L327-L336
 
-function expandTimeRange(startTime: number, endTime: number, step: number): [number, number] {
-  // startTime is decreased to the closes multiple-of-step, if necessary
-  const newStartTime = startTime - (startTime % step);
-
-  // endTime is increased to the closed multiple-of-step, if necessary
-  let newEndTime = endTime;
-  const endStepMod = endTime % step;
-  if (endStepMod !== 0) {
-    newEndTime += step - endStepMod;
-  }
-
-  return [newStartTime, newEndTime];
-}
-
 export function splitTimeRange(
   startTime: number,
   endTime: number,
@@ -33,20 +19,19 @@ export function splitTimeRange(
   // we make the duration a multiple of `step`, lowering it if necessary
   const alignedDuration = Math.trunc(idealRangeDuration / step) * step;
 
-  const [alignedStartTime, alignedEndTime] = expandTimeRange(startTime, endTime, step);
+  const alignedStartTime = startTime - (startTime % step);
 
   const result: Array<[number, number]> = [];
 
-  // we iterate it from the end, because we want to have the potentially smaller chunk at the end, not at the beginning
+  // in a previous version we started iterating from the end, to the start.
-  for (let chunkEndTime = alignedEndTime; chunkEndTime > alignedStartTime; chunkEndTime -= alignedDuration + step) {
+  // However this is not easily possible as end timestamps are always inclusive
-    // when we get close to the start of the time range, we need to be sure not
+  // for Loki. So a `2022-02-08T00:00:00Z` end time with a 1day step would mean
-    // to cross over the startTime
+  // to include the 08.02.2022, which we don't want. So we have to start from
-    const chunkStartTime = Math.max(chunkEndTime - alignedDuration, alignedStartTime);
+  // the start, always ending at the last step before the actual end, or the total end.
+  for (let chunkStartTime = alignedStartTime; chunkStartTime < endTime; chunkStartTime += alignedDuration) {
+    const chunkEndTime = Math.min(chunkStartTime + alignedDuration - step, endTime);
     result.push([chunkStartTime, chunkEndTime]);
   }
 
-  // because we walked backwards, we need to reverse the array
-  result.reverse();
-
   return result;
 }

public/app/plugins/datasource/loki/querySplitting.test.ts

@@ -82,8 +82,8 @@ describe('runSplitQuery()', () => {
           intervalMs: 60000,
           range: expect.objectContaining({
             from: expect.objectContaining({
-              //2023-02-09T06:00:00.000Z
+              //2023-02-10T05:00:00.000Z
-              _i: 1675922400000,
+              _i: 1676005200000,
             }),
             to: expect.objectContaining({
               // 2023-02-10T06:00:00.000Z
@@ -100,12 +100,12 @@ describe('runSplitQuery()', () => {
           intervalMs: 60000,
           range: expect.objectContaining({
             from: expect.objectContaining({
-              //2023-02-08T05:59:00.000Z
+              // 2023-02-09T05:00:00.000Z
-              _i: 1675835940000,
+              _i: 1675918800000,
             }),
             to: expect.objectContaining({
-              // 2023-02-09T05:59:00.000Z
+              // 2023-02-10T04:59:00.000Z
-              _i: 1675922340000,
+              _i: 1676005140000,
             }),
           }),
         })
@@ -118,12 +118,12 @@ describe('runSplitQuery()', () => {
           intervalMs: 60000,
           range: expect.objectContaining({
             from: expect.objectContaining({
-              //2023-02-08T05:00:00.000Z
+              // 2023-02-08T05:00:00.000Z
               _i: 1675832400000,
             }),
             to: expect.objectContaining({
-              // 2023-02-08T05:58:00.000Z
+              // 2023-02-09T04:59:00.000Z
-              _i: 1675835880000,
+              _i: 1675918740000,
             }),
           }),
         })
@@ -142,8 +142,8 @@ describe('runSplitQuery()', () => {
           intervalMs: 60000,
           range: expect.objectContaining({
             from: expect.objectContaining({
-              //2023-02-09T06:00:00.000Z
+              //2023-02-10T05:00:00.000Z
-              _i: 1675922400000,
+              _i: 1676005200000,
             }),
             to: expect.objectContaining({
               // 2023-02-10T06:00:00.000Z
@@ -160,12 +160,12 @@ describe('runSplitQuery()', () => {
           intervalMs: 60000,
           range: expect.objectContaining({
             from: expect.objectContaining({
-              //2023-02-08T05:59:50.000Z
+              // 2023-02-09T05:00:00.000Z
-              _i: 1675835990000,
+              _i: 1675918800000,
             }),
             to: expect.objectContaining({
-              // 2023-02-09T05:59:50.000Z
+              // 2023-02-10T04:59:50.000Z
-              _i: 1675922390000,
+              _i: 1676005190000,
             }),
           }),
         })
@@ -182,8 +182,8 @@ describe('runSplitQuery()', () => {
               _i: 1675832400000,
             }),
             to: expect.objectContaining({
-              // 2023-02-08T05:59:40.000Z
+              // 2023-02-09T04:59:50.000Z
-              _i: 1675835980000,
+              _i: 1675918790000,
             }),
           }),
         })