loki: use metadataRequest in testDatasource (#48431)

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

@@ -534,74 +534,56 @@ describe('LokiDatasource', () => {
   });
 
   describe('when performing testDataSource', () => {
-    describe('and call succeeds', () => {
+    it('should return successfully when call succeeds with labels', async () => {
-      it('should return successfully', async () => {
-        fetchMock.mockImplementation(() => of(createFetchResponse({ values: ['avalue'] })));
       const ds = createLokiDSForTests({} as TemplateSrv);
+      ds.metadataRequest = () => Promise.resolve(['avalue']);
 
       const result = await ds.testDatasource();
 
-        expect(result.status).toBe('success');
+      expect(result).toStrictEqual({
+        status: 'success',
+        message: 'Data source connected and labels found.',
       });
     });
 
-    describe('and call fails with 401 error', () => {
+    it('should return error when call succeeds without labels', async () => {
-      it('should return error status and a detailed error message', async () => {
+      const ds = createLokiDSForTests({} as TemplateSrv);
-        fetchMock.mockImplementation(() =>
+      ds.metadataRequest = () => Promise.resolve([]);
-          throwError({
+
-            statusText: 'Unauthorized',
+      const result = await ds.testDatasource();
-            status: 401,
+
+      expect(result).toStrictEqual({
+        status: 'error',
+        message: 'Data source connected, but no labels received. Verify that Loki and Promtail is configured properly.',
+      });
+    });
+
+    it('should return error status with no details when call fails with no details', async () => {
+      const ds = createLokiDSForTests({} as TemplateSrv);
+      ds.metadataRequest = () => Promise.reject({});
+
+      const result = await ds.testDatasource();
+
+      expect(result).toStrictEqual({
+        status: 'error',
+        message: 'Unable to fetch labels from Loki, please check the server logs for more details',
+      });
+    });
+
+    it('should return error status with details when call fails with details', async () => {
+      const ds = createLokiDSForTests({} as TemplateSrv);
+      ds.metadataRequest = () =>
+        Promise.reject({
           data: {
-              message: 'Unauthorized',
+            message: 'error42',
           },
-          })
+        });
-        );
-        const ds = createLokiDSForTests({} as TemplateSrv);
 
       const result = await ds.testDatasource();
 
-        expect(result.status).toEqual('error');
+      expect(result).toStrictEqual({
-        expect(result.message).toBe('Loki: Unauthorized. 401. Unauthorized');
+        status: 'error',
-      });
+        message: 'Unable to fetch labels from Loki (error42), please check the server logs for more details',
-    });
-
-    describe('and call fails with 404 error', () => {
-      it('should return error status and a detailed error message', async () => {
-        fetchMock.mockImplementation(() =>
-          throwError({
-            statusText: 'Not found',
-            status: 404,
-            data: {
-              message: '404 page not found',
-            },
-          })
-        );
-
-        const ds = createLokiDSForTests({} as TemplateSrv);
-
-        const result = await ds.testDatasource();
-
-        expect(result.status).toEqual('error');
-        expect(result.message).toBe('Loki: Not found. 404. 404 page not found');
-      });
-    });
-
-    describe('and call fails with 502 error', () => {
-      it('should return error status and a detailed error message', async () => {
-        fetchMock.mockImplementation(() =>
-          throwError({
-            statusText: 'Bad Gateway',
-            status: 502,
-            data: '',
-          })
-        );
-
-        const ds = createLokiDSForTests({} as TemplateSrv);
-
-        const result = await ds.testDatasource();
-
-        expect(result.status).toEqual('error');
-        expect(result.message).toBe('Loki: Bad Gateway. 502');
       });
     });
   });

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

@@ -689,44 +689,35 @@ export class LokiDatasource
     };
   };
 
-  testDatasource() {
+  testDatasource(): Promise<{ status: string; message: string }> {
     // Consider only last 10 minutes otherwise request takes too long
-    const startMs = Date.now() - 10 * 60 * 1000;
+    const nowMs = Date.now();
-    const start = `${startMs}000000`; // API expects nanoseconds
+    const params = {
-    return lastValueFrom(
+      start: (nowMs - 10 * 60 * 1000) * NS_IN_MS,
-      this._request(`${LOKI_ENDPOINT}/label`, { start }).pipe(
+      end: nowMs * NS_IN_MS,
-        map((res) => {
+    };
-          const values: any[] = res?.data?.data || res?.data?.values || [];
+
-          const testResult =
+    return this.metadataRequest('labels', params).then(
-            values.length > 0
+      (values) => {
+        return values.length > 0
           ? { status: 'success', message: 'Data source connected and labels found.' }
           : {
               status: 'error',
               message:
                 'Data source connected, but no labels received. Verify that Loki and Promtail is configured properly.',
             };
-          return testResult;
+      },
-        }),
+      (err) => {
-        catchError((err: any) => {
+        // we did a resource-call that failed.
-          let message = 'Loki: ';
+        // the only info we have, if exists, is err.data.message
-          if (err.statusText) {
+        // (when in development-mode, err.data.error exists too, but not in production-mode)
-            message += err.statusText;
+        // things like err.status & err.statusText does not help,
-          } else {
+        // because those will only describe how the request between browser<>server failed
-            message += 'Cannot connect to Loki';
+        const info: string = err?.data?.message ?? '';
+        const infoInParentheses = info !== '' ? ` (${info})` : '';
+        const message = `Unable to fetch labels from Loki${infoInParentheses}, please check the server logs for more details`;
+        return { status: 'error', message: message };
       }
-
-          if (err.status) {
-            message += `. ${err.status}`;
-          }
-
-          if (err.data && err.data.message) {
-            message += `. ${err.data.message}`;
-          } else if (err.data) {
-            message += `. ${err.data}`;
-          }
-          return of({ status: 'error', message: message });
-        })
-      )
     );
   }