update metadata fetch

packages/grafana-prometheus/src/language_provider.test.ts

@@ -725,6 +725,136 @@ describe('Prometheus Language Provider', () => {
       );
     });
   });
+
+  describe('getMetricsMetadata', () => {
+    it('should fetch metadata if not already loaded', async () => {
+      const mockMetadata = {
+        metric1: [
+          {
+            type: 'counter',
+            help: 'help text 1',
+          },
+        ],
+        metric2: [
+          {
+            type: 'gauge',
+            help: 'help text 2',
+          },
+        ],
+      };
+
+      const expectedMetadata = {
+        metric1: {
+          type: 'counter',
+          help: 'help text 1',
+        },
+        metric2: {
+          type: 'gauge',
+          help: 'help text 2',
+        },
+      };
+
+      const languageProvider = new LanguageProvider({
+        ...defaultDatasource,
+        metadataRequest: () => ({ data: { data: mockMetadata } }),
+      } as unknown as PrometheusDatasource);
+
+      const requestSpy = jest.spyOn(languageProvider, 'request');
+
+      const result = await languageProvider.getMetricsMetadata();
+
+      expect(requestSpy).toHaveBeenCalledWith(
+        '/api/v1/metadata',
+        {},
+        {
+          showErrorAlert: false,
+          headers: { 'X-Grafana-Cache': 'private, max-age=86400' },
+        }
+      );
+      expect(result).toEqual(expect.objectContaining(expectedMetadata));
+    });
+
+    it('should return cached metadata without fetching if already loaded', async () => {
+      const mockMetadata = {
+        metric1: [
+          {
+            type: 'counter',
+            help: 'help text 1',
+          },
+        ],
+      };
+
+      const expectedMetadata = {
+        metric1: {
+          type: 'counter',
+          help: 'help text 1',
+        },
+      };
+
+      const languageProvider = new LanguageProvider({
+        ...defaultDatasource,
+        metadataRequest: () => ({ data: { data: mockMetadata } }),
+      } as unknown as PrometheusDatasource);
+
+      // First call to load metadata
+      const firstResult = await languageProvider.getMetricsMetadata();
+      expect(firstResult).toEqual(expect.objectContaining(expectedMetadata));
+
+      const requestSpy = jest.spyOn(languageProvider, 'request');
+
+      // Second call should use cached data
+      const result = await languageProvider.getMetricsMetadata();
+
+      expect(requestSpy).not.toHaveBeenCalled();
+      expect(result).toEqual(expect.objectContaining(expectedMetadata));
+    });
+
+    it('should handle empty metadata response', async () => {
+      const languageProvider = new LanguageProvider({
+        ...defaultDatasource,
+        metadataRequest: () => ({ data: { data: {} } }),
+      } as unknown as PrometheusDatasource);
+
+      const result = await languageProvider.getMetricsMetadata();
+
+      // Even with empty input, fixSummariesMetadata might add some default entries
+      expect(Object.keys(result).length).toBeGreaterThanOrEqual(0);
+    });
+
+    it('should handle error during metadata fetch', async () => {
+      jest.spyOn(console, 'error').mockImplementation();
+      const languageProvider = new LanguageProvider({
+        ...defaultDatasource,
+        metadataRequest: () => Promise.reject(new Error('Metadata fetch failed')),
+      } as unknown as PrometheusDatasource);
+
+      const result = await languageProvider.getMetricsMetadata();
+
+      expect(result).toEqual(undefined);
+    });
+
+    it('should use configured cache duration from datasource', async () => {
+      const mockDays = 7;
+      const languageProvider = new LanguageProvider({
+        ...defaultDatasource,
+        getDaysToCacheMetadata: () => mockDays,
+        metadataRequest: () => ({ data: { data: {} } }),
+      } as unknown as PrometheusDatasource);
+
+      const requestSpy = jest.spyOn(languageProvider, 'request');
+
+      await languageProvider.getMetricsMetadata();
+
+      expect(requestSpy).toHaveBeenCalledWith(
+        '/api/v1/metadata',
+        {},
+        {
+          showErrorAlert: false,
+          headers: { 'X-Grafana-Cache': `private, max-age=${mockDays * 86400}` },
+        }
+      );
+    });
+  });
 });
 
 describe('removeQuotesIfExist', () => {

packages/grafana-prometheus/src/language_provider.ts

@@ -84,13 +84,19 @@ const getDefaultCacheHeaders = (cacheLevel: PrometheusCacheLevel) => {
 };
 
 export default class PromQlLanguageProvider extends LanguageProvider {
+  declare startTask: Promise<any>;
+  declare labelFetchTs: number;
+
+  private _metricsMetadata?: PromMetricsMetadata;
+
   histogramMetrics: string[];
   metrics: string[];
+  /**
+   * @deprecated Use getMetricsMetadata() method instead
+   */
   metricsMetadata?: PromMetricsMetadata;
-  declare startTask: Promise<any>;
   datasource: PrometheusDatasource;
   labelKeys: string[] = [];
-  declare labelFetchTs: number;
 
   constructor(datasource: PrometheusDatasource, initialValues?: Partial<PromQlLanguageProvider>) {
     super();
@@ -142,7 +148,7 @@ export default class PromQlLanguageProvider extends LanguageProvider {
    *
    * @returns {Promise<PromMetricsMetadata>} Promise that resolves when metadata has been fetched
    */
-  fetchMetadata = async () => {
+  private _fetchMetadata = async () => {
     const secondsInDay = 86400;
     const headers = buildCacheHeaders(this.datasource.getDaysToCacheMetadata() * secondsInDay);
     const metadata = await this.request(
@@ -153,8 +159,7 @@ export default class PromQlLanguageProvider extends LanguageProvider {
         ...headers,
       }
     );
-    this.metricsMetadata = fixSummariesMetadata(metadata);
-    return this.metricsMetadata;
+    return fixSummariesMetadata(metadata);
   };
 
   // ===================================
@@ -256,11 +261,32 @@ export default class PromQlLanguageProvider extends LanguageProvider {
 
   // ======================================================================
 
+  public getMetricsMetadata = async (): Promise<PromMetricsMetadata> => {
+    if (!this._metricsMetadata) {
+      this._metricsMetadata = await this._fetchMetadata();
+    }
+
+    return this._metricsMetadata;
+  };
+
+  // ======================================================================
+
   /**
-   * @deprecated Use fetchMetadata instead
+   * @deprecated Use _fetchMetadata instead. If you want metadata itself use getMetricsMetadata() method.
    */
   async loadMetricsMetadata() {
-    this.fetchMetadata();
+    const secondsInDay = 86400;
+    const headers = buildCacheHeaders(this.datasource.getDaysToCacheMetadata() * secondsInDay);
+    this.metricsMetadata = fixSummariesMetadata(
+      await this.request(
+        API_V1.METADATA,
+        {},
+        {
+          showErrorAlert: false,
+          ...headers,
+        }
+      )
+    );
   }
 
   getLabelKeys(): string[] {