Loki: Interpolate variables in live queries (#83831)

* Loki: Interpolate variables in live queries

* Update to not have to rempve private

* Update comment

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

@@ -18,6 +18,7 @@ import {
   TimeRange,
   ToggleFilterAction,
   DataQueryRequest,
+  ScopedVars,
 } from '@grafana/data';
 import {
   BackendSrv,
@@ -1652,6 +1653,19 @@ describe('LokiDatasource', () => {
       }).rejects.toThrow('invalid metadata request url: /index');
     });
   });
+
+  describe('live tailing', () => {
+    it('interpolates variables with scopedVars and filters', () => {
+      const ds = createLokiDatasource();
+      const query: LokiQuery = { expr: '{app=$app}', refId: 'A' };
+      const scopedVars: ScopedVars = { app: { text: 'interpolated', value: 'interpolated' } };
+      const filters: AdHocFilter[] = [];
+
+      jest.spyOn(ds, 'applyTemplateVariables').mockImplementation((query) => query);
+      ds.query({ targets: [query], scopedVars, filters, liveStreaming: true } as DataQueryRequest<LokiQuery>);
+      expect(ds.applyTemplateVariables).toHaveBeenCalledWith(expect.objectContaining(query), scopedVars, filters);
+    });
+  });
 });
 
 describe('applyTemplateVariables', () => {

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

@@ -300,7 +300,7 @@ export class LokiDatasource
       return merge(
         ...streamQueries.map((q) =>
           doLokiChannelStream(
-            this.applyTemplateVariables(q, request.scopedVars),
+            this.applyTemplateVariables(q, request.scopedVars, request.filters),
             this, // the datasource
             streamRequest
           )
@@ -340,15 +340,13 @@ export class LokiDatasource
 
   /**
    * Used within the `query` to execute live queries.
-   * It is intended for explore-mode and logs-queries, not metric queries.
+   * It is intended for logs-queries, not metric queries.
    * @returns An Observable of DataQueryResponse with live query results or an empty response if no suitable queries are found.
    * @todo: The name says "backend" but it's actually running the query through the frontend. We should fix this.
    */
   private runLiveQueryThroughBackend(request: DataQueryRequest<LokiQuery>): Observable<DataQueryResponse> {
-    // this only works in explore-mode so variables don't need to be handled,
     // and only for logs-queries, not metric queries
     const logsQueries = request.targets.filter((query) => query.expr !== '' && isLogsQuery(query.expr));
-
     if (logsQueries.length === 0) {
       return of({
         data: [],
@@ -357,9 +355,10 @@ export class LokiDatasource
     }
 
     const subQueries = logsQueries.map((query) => {
-      const maxDataPoints = query.maxLines || this.maxLines;
+      const interpolatedQuery = this.applyTemplateVariables(query, request.scopedVars, request.filters);
+      const maxDataPoints = interpolatedQuery.maxLines || this.maxLines;
       // FIXME: currently we are running it through the frontend still.
-      return this.runLiveQuery(query, maxDataPoints);
+      return this.runLiveQuery(interpolatedQuery, maxDataPoints);
     });
 
     return merge(...subQueries);