Range splitting: Read errors from the received response and report them (#63368)

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

@@ -2,6 +2,7 @@ import { of } from 'rxjs';
 import { getQueryOptions } from 'test/helpers/getQueryOptions';
 
 import { dateTime } from '@grafana/data';
+import { LoadingState } from '@grafana/schema';
 
 import { LokiDatasource } from './datasource';
 import * as logsTimeSplit from './logsTimeSplit';
@@ -36,6 +37,15 @@ describe('runPartitionedQuery()', () => {
     });
   });
 
+  test('Handles and reports rerrors', async () => {
+    jest
+      .spyOn(datasource, 'runQuery')
+      .mockReturnValue(of({ state: LoadingState.Error, error: { refId: 'A', message: 'Error' }, data: [] }));
+    await expect(runPartitionedQuery(datasource, request)).toEmitValuesWith((values) => {
+      expect(values).toEqual([{ refId: 'A', message: 'Error' }]);
+    });
+  });
+
   describe('Hidden queries', () => {
     const request = getQueryOptions<LokiQuery>({
       targets: [

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

@@ -1,4 +1,4 @@
-import { Subscriber, map, Observable, Subscription } from 'rxjs';
+import { Subscriber, Observable, Subscription } from 'rxjs';
 
 import { DataQueryRequest, DataQueryResponse, dateTime, TimeRange } from '@grafana/data';
 import { LoadingState } from '@grafana/schema';
@@ -103,6 +103,7 @@ export function runPartitionedQuery(datasource: LokiDatasource, request: DataQue
   let subquerySubsciption: Subscription | null = null;
   const runNextRequest = (subscriber: Subscriber<DataQueryResponse>, requestN: number) => {
     if (shouldStop) {
+      subscriber.complete();
       return;
     }
 
@@ -116,34 +117,36 @@ export function runPartitionedQuery(datasource: LokiDatasource, request: DataQue
       subscriber.complete();
     };
 
+    const nextRequest = () => {
+      mergedResponse = mergedResponse || { data: [] };
+      if (requestN > 1) {
+        mergedResponse.state = LoadingState.Streaming;
+        subscriber.next(mergedResponse);
+        runNextRequest(subscriber, requestN - 1);
+        return;
+      }
+      done(mergedResponse);
+    };
+
     if (!targets.length && mergedResponse) {
       done(mergedResponse);
       return;
     }
 
-    subquerySubsciption = datasource
-      .runQuery({ ...request, range, requestId, targets })
-      .pipe(
-        // in case of an empty query, this is somehow run twice. `share()` is no workaround here as the observable is generated from `of()`.
-        map((partialResponse) => {
-          mergedResponse = combineResponses(mergedResponse, partialResponse);
-          return mergedResponse;
-        })
-      )
-      .subscribe({
-        next: (response) => {
-          if (requestN > 1) {
-            response.state = LoadingState.Streaming;
-            subscriber.next(response);
-            runNextRequest(subscriber, requestN - 1);
-            return;
-          }
-          done(response);
-        },
-        error: (error) => {
-          subscriber.error(error);
-        },
-      });
+    subquerySubsciption = datasource.runQuery({ ...request, range, requestId, targets }).subscribe({
+      next: (partialResponse) => {
+        if (partialResponse.error) {
+          subscriber.error(partialResponse.error);
+        }
+        mergedResponse = combineResponses(mergedResponse, partialResponse);
+      },
+      complete: () => {
+        nextRequest();
+      },
+      error: (error) => {
+        subscriber.error(error);
+      },
+    });
   };
 
   const response = new Observable<DataQueryResponse>((subscriber) => {