Loki: Re-introduce running of instant queries (#27213)

* Run instant queries for loki

* Add catch for instant query errors, update test

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

@@ -114,7 +114,7 @@ describe('LokiDatasource', () => {
       datasourceRequestMock.mockImplementation(() => Promise.resolve(testResp));
     });
 
-    test('should just run range query when in logs mode', async () => {
+    test('should run range and instant query', async () => {
       const options = getQueryOptions<LokiQuery>({
         targets: [{ expr: '{job="grafana"}', refId: 'B' }],
       });
@@ -123,7 +123,7 @@ describe('LokiDatasource', () => {
       ds.runRangeQuery = jest.fn(() => of({ data: [] }));
       await ds.query(options).toPromise();
 
-      expect(ds.runInstantQuery).not.toBeCalled();
+      expect(ds.runInstantQuery).toBeCalled();
       expect(ds.runRangeQuery).toBeCalled();
     });
 
@@ -185,7 +185,7 @@ describe('LokiDatasource', () => {
       const ds = new LokiDatasource(customSettings, templateSrvMock);
 
       datasourceRequestMock.mockImplementation(
-        jest.fn().mockReturnValueOnce(
+        jest.fn().mockReturnValue(
           Promise.reject({
             data: {
               message: 'parse error at line 1, col 6: invalid char escape',
@@ -494,7 +494,7 @@ function makeLimitTest(instanceSettings: any, datasourceRequestMock: any, templa
 
     ds.query(options);
 
-    expect(datasourceRequestMock.mock.calls.length).toBe(1);
+    expect(datasourceRequestMock.mock.calls.length).toBe(2);
     expect(datasourceRequestMock.mock.calls[0][0].url).toContain(`limit=${expectedLimit}`);
   };
 }

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

@@ -91,7 +91,12 @@ export class LokiDatasource extends DataSourceApi<LokiQuery, LokiOptions> {
         expr: this.templateSrv.replace(target.expr, options.scopedVars, this.interpolateQueryExpr),
       }));
 
-    filteredTargets.forEach(target => subQueries.push(this.runRangeQuery(target, options, filteredTargets.length)));
+    filteredTargets.forEach(target =>
+      subQueries.push(
+        this.runInstantQuery(target, options, filteredTargets.length),
+        this.runRangeQuery(target, options, filteredTargets.length)
+      )
+    );
 
     // No valid targets, return the empty result to save a round trip.
     if (isEmpty(subQueries)) {
@@ -133,7 +138,8 @@ export class LokiDatasource extends DataSourceApi<LokiQuery, LokiOptions> {
           data: [lokiResultsToTableModel(response.data.data.result, responseListLength, target.refId, meta, true)],
           key: `${target.refId}_instant`,
         };
-      })
+      }),
+      catchError((err: any) => this.throwUnless(err, err.status === 404, target))
     );
   };