Prometheus: Fix query interval string interpolation in query cache (#93678)

fix query interval string interpolation in query cache

packages/grafana-prometheus/src/datasource.ts

@@ -141,6 +141,7 @@ export class PrometheusDatasource
     this.cache = new QueryCache({
       getTargetSignature: this.getPrometheusTargetSignature.bind(this),
       overlapString: instanceSettings.jsonData.incrementalQueryOverlapWindow ?? defaultPrometheusQueryOverlapWindow,
+      applyInterpolation: this.interpolateString.bind(this),
     });
 
     // This needs to be here and cannot be static because of how annotations typing affects casting of data source

packages/grafana-prometheus/src/querycache/QueryCache.test.ts

@@ -6,7 +6,7 @@ import { DataFrame, DataQueryRequest, DateTime, dateTime, TimeRange } from '@gra
 import { QueryEditorMode } from '../querybuilder/shared/types';
 import { PromQuery } from '../types';
 
-import { CacheRequestInfo, QueryCache } from './QueryCache';
+import { CacheRequestInfo, findDatapointStep, QueryCache } from './QueryCache';
 import { IncrementalStorageDataFrameScenarios, trimmedFirstPointInPromFrames } from './QueryCacheTestData';
 
 // Will not interpolate vars!
@@ -559,3 +559,14 @@ describe('QueryCache: Prometheus', function () {
     expect(cacheRequest.shouldCache).toBe(true);
   });
 });
+
+describe('findDataPointStep', () => {
+  it('should interpolate custom interval', () => {
+    const mockApplyInterpolation = jest.fn().mockImplementation(() => '1m');
+    const req = mockPromRequest();
+    req.targets[0].interval = '$interval';
+    const respFrames = trimmedFirstPointInPromFrames as unknown as DataFrame[];
+    findDatapointStep(req, respFrames, mockApplyInterpolation);
+    expect(mockApplyInterpolation).toBeCalledTimes(1);
+  });
+});

packages/grafana-prometheus/src/querycache/QueryCache.ts

@@ -10,6 +10,7 @@ import {
   isValidDuration,
   parseDuration,
   rangeUtil,
+  ScopedVars,
   Table,
   trimTable,
 } from '@grafana/data';
@@ -23,10 +24,9 @@ type TargetIdent = string;
 // query + template variables + interval + raw time range
 // used for full target cache busting -> full range re-query
 type TargetSig = string;
-
 type TimestampMs = number;
-
 type SupportedQueryTypes = PromQuery;
+type ApplyInterpolation = (str: string, scopedVars?: ScopedVars) => string;
 
 // string matching requirements defined in durationutil.ts
 export const defaultPrometheusQueryOverlapWindow = '10m';
@@ -59,12 +59,14 @@ export const getFieldIdent = (field: Field) => `${field.type}|${field.name}|${JS
 export class QueryCache<T extends SupportedQueryTypes> {
   private overlapWindowMs: number;
   private getTargetSignature: (request: DataQueryRequest<T>, target: T) => string;
+  private applyInterpolation = (str: string, scopedVars?: ScopedVars) => str;
 
   cache = new Map<TargetIdent, TargetCache>();
 
   constructor(options: {
     getTargetSignature: (request: DataQueryRequest<T>, target: T) => string;
     overlapString: string;
+    applyInterpolation?: ApplyInterpolation;
   }) {
     const unverifiedOverlap = options.overlapString;
     if (isValidDuration(unverifiedOverlap)) {
@@ -76,6 +78,9 @@ export class QueryCache<T extends SupportedQueryTypes> {
     }
 
     this.getTargetSignature = options.getTargetSignature;
+    if (options.applyInterpolation) {
+      this.applyInterpolation = options.applyInterpolation;
+    }
   }
 
   // can be used to change full range request to partial, split into multiple requests
@@ -221,7 +226,7 @@ export class QueryCache<T extends SupportedQueryTypes> {
           // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
           let table: Table = frame.fields.map((field) => field.values) as Table;
 
-          const dataPointStep = findDatapointStep(request, respFrames);
+          const dataPointStep = findDatapointStep(request, respFrames, this.applyInterpolation);
 
           // query interval is greater than request.intervalMs, use query interval to make sure we've always got one datapoint outside the panel viewport
           let trimmed = trimTable(table, newFrom - dataPointStep, newTo);
@@ -260,7 +265,11 @@ export class QueryCache<T extends SupportedQueryTypes> {
   }
 }
 
-function findDatapointStep(request: DataQueryRequest<PromQuery>, respFrames: DataFrame[]): number {
+export function findDatapointStep(
+  request: DataQueryRequest<PromQuery>,
+  respFrames: DataFrame[],
+  applyInterpolation: ApplyInterpolation
+): number {
   // Prometheus specific logic below
   if (request.targets[0].datasource?.type !== 'prometheus') {
     return 0;
@@ -270,7 +279,7 @@ function findDatapointStep(request: DataQueryRequest<PromQuery>, respFrames: Dat
 
   let dataPointStep = request.intervalMs;
   if (target?.interval) {
-    const minStepMs = rangeUtil.intervalToMs(target.interval);
+    const minStepMs = rangeUtil.intervalToMs(applyInterpolation(target.interval));
     if (minStepMs > request.intervalMs) {
       dataPointStep = minStepMs;
     }