Loki: Add support for "label_values(log stream selector, label)" in templating (#35488)

* Use series endpoint if we have queries expr

* Update documentation

docs/sources/datasources/loki.md

@@ -148,10 +148,11 @@ Check out the [Templating]({{< relref "../variables/_index.md" >}}) documentatio
 Variable of the type _Query_ allows you to query Loki for a list labels or label values. The Loki data source plugin
 provides the following functions you can use in the `Query` input field.
 
-| Name                  | Description                                                     |
-| --------------------- | --------------------------------------------------------------- |
-| `label_names()`       | Returns a list of label names.                                  |
-| `label_values(label)` | Returns a list of label values for the `label` in every metric. |
+| Name                                       | Description                                                                          |
+| -------------------------------------------| -------------------------------------------------------------------------------------|
+| `label_names()`                            | Returns a list of label names.                                                       |
+| `label_values(label)`                      | Returns a list of label values for the `label`.                                      |
+| `label_values(log stream selector, label)` | Returns a list of label values for the `label` in the specified `log stream selector`.|
 
 ## Annotations
 

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

@@ -548,42 +548,46 @@ describe('LokiDatasource', () => {
   describe('metricFindQuery', () => {
     const getTestContext = (mock: LokiDatasource) => {
       const ds = createLokiDSForTests();
-      ds.getVersion = mock.getVersion;
       ds.metadataRequest = mock.metadataRequest;
 
       return { ds };
     };
 
-    const mocks = makeMetadataAndVersionsMocks();
+    const mock = makeMockLokiDatasource(
+      { label1: ['value1', 'value2'], label2: ['value3', 'value4'] },
+      { '{label1="value1", label2="value2"}': [{ label5: 'value5' }] }
+    );
 
-    mocks.forEach((mock, index) => {
-      it(`should return label names for Loki v${index}`, async () => {
-        const { ds } = getTestContext(mock);
+    it(`should return label names for Loki`, async () => {
+      const { ds } = getTestContext(mock);
 
-        const res = await ds.metricFindQuery('label_names()');
+      const res = await ds.metricFindQuery('label_names()');
 
-        expect(res).toEqual([{ text: 'label1' }, { text: 'label2' }]);
-      });
+      expect(res).toEqual([{ text: 'label1' }, { text: 'label2' }]);
     });
 
-    mocks.forEach((mock, index) => {
-      it(`should return label values for Loki v${index}`, async () => {
-        const { ds } = getTestContext(mock);
+    it(`should return label values for Loki when no matcher`, async () => {
+      const { ds } = getTestContext(mock);
 
-        const res = await ds.metricFindQuery('label_values(label1)');
+      const res = await ds.metricFindQuery('label_values(label1)');
 
-        expect(res).toEqual([{ text: 'value1' }, { text: 'value2' }]);
-      });
+      expect(res).toEqual([{ text: 'value1' }, { text: 'value2' }]);
     });
 
-    mocks.forEach((mock, index) => {
-      it(`should return empty array when incorrect query for Loki v${index}`, async () => {
-        const { ds } = getTestContext(mock);
+    it(`should return label values for Loki with matcher`, async () => {
+      const { ds } = getTestContext(mock);
 
-        const res = await ds.metricFindQuery('incorrect_query');
+      const res = await ds.metricFindQuery('label_values({label1="value1", label2="value2"},label5)');
 
-        expect(res).toEqual([]);
-      });
+      expect(res).toEqual([{ text: 'value5' }]);
+    });
+
+    it(`should return empty array when incorrect query for Loki`, async () => {
+      const { ds } = getTestContext(mock);
+
+      const res = await ds.metricFindQuery('incorrect_query');
+
+      expect(res).toEqual([]);
     });
   });
 });
@@ -629,13 +633,3 @@ function makeAnnotationQueryRequest(options: any): AnnotationQueryRequest<LokiQu
     rangeRaw: timeRange,
   };
 }
-
-function makeMetadataAndVersionsMocks() {
-  const mocks = [];
-  for (let i = 0; i <= 1; i++) {
-    const mock: LokiDatasource = makeMockLokiDatasource({ label1: ['value1', 'value2'], label2: ['value3', 'value4'] });
-    mock.getVersion = jest.fn().mockReturnValue(`v${i}`);
-    mocks.push(mock);
-  }
-  return mocks;
-}

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

@@ -313,32 +313,55 @@ export class LokiDatasource extends DataSourceApi<LokiQuery, LokiOptions> {
     const labelNamesRegex = /^label_names\(\)\s*$/;
     const labelValuesRegex = /^label_values\((?:(.+),\s*)?([a-zA-Z_][a-zA-Z0-9_]*)\)\s*$/;
 
-    const params = this.getTimeRangeParams();
     const labelNames = query.match(labelNamesRegex);
     if (labelNames) {
-      return await this.labelNamesQuery(params);
+      return await this.labelNamesQuery();
     }
 
     const labelValues = query.match(labelValuesRegex);
     if (labelValues) {
-      return await this.labelValuesQuery(labelValues[2], params);
+      // If we have query expr, use /series endpoint
+      if (labelValues[1]) {
+        return await this.labelValuesSeriesQuery(labelValues[1], labelValues[2]);
+      }
+      return await this.labelValuesQuery(labelValues[2]);
     }
 
     return Promise.resolve([]);
   }
 
-  async labelNamesQuery(params?: Record<string, string | number>) {
+  async labelNamesQuery() {
     const url = `${LOKI_ENDPOINT}/label`;
+    const params = this.getTimeRangeParams();
     const result = await this.metadataRequest(url, params);
     return result.map((value: string) => ({ text: value }));
   }
 
-  async labelValuesQuery(label: string, params?: Record<string, string | number>) {
+  async labelValuesQuery(label: string) {
+    const params = this.getTimeRangeParams();
     const url = `${LOKI_ENDPOINT}/label/${label}/values`;
     const result = await this.metadataRequest(url, params);
     return result.map((value: string) => ({ text: value }));
   }
 
+  async labelValuesSeriesQuery(expr: string, label: string) {
+    const timeParams = this.getTimeRangeParams();
+    const params = {
+      ...timeParams,
+      match: expr,
+    };
+    const url = `${LOKI_ENDPOINT}/series`;
+    const streams = new Set();
+    const result = await this.metadataRequest(url, params);
+    result.forEach((stream: { [key: string]: string }) => {
+      if (stream[label]) {
+        streams.add({ text: stream[label] });
+      }
+    });
+
+    return Array.from(streams);
+  }
+
   interpolateQueryExpr(value: any, variable: any) {
     // if no multi or include all do not regexEscape
     if (!variable.multi && !variable.includeAll) {