Loki: Add optional stream selector to fetchLabelValues API (#77207)

* Loki: Add optional stream selector to fetchLabelValues API

* Update public/app/plugins/datasource/loki/docs/app_plugin_developer_documentation.md

Co-authored-by: Sven Grossmann <sven.grossmann@grafana.com>

* Update tests

---------

Co-authored-by: Sven Grossmann <sven.grossmann@grafana.com>

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

@@ -233,7 +233,23 @@ describe('Language completion provider', () => {
       const provider = await getLanguageProvider(datasource);
       const requestSpy = jest.spyOn(provider, 'request');
       const labelValues = await provider.fetchLabelValues('testkey');
-      expect(requestSpy).toHaveBeenCalled();
+      expect(requestSpy).toHaveBeenCalledWith('label/testkey/values', {
+        end: 1560163909000,
+        start: 1560153109000,
+      });
+      expect(labelValues).toEqual(['label1_val1', 'label1_val2']);
+    });
+
+    it('fetch label when options.streamSelector provided and values is not cached', async () => {
+      const datasource = setup({ testkey: ['label1_val1', 'label1_val2'], label2: [] });
+      const provider = await getLanguageProvider(datasource);
+      const requestSpy = jest.spyOn(provider, 'request');
+      const labelValues = await provider.fetchLabelValues('testkey', { streamSelector: '{foo="bar"}' });
+      expect(requestSpy).toHaveBeenCalledWith('label/testkey/values', {
+        end: 1560163909000,
+        query: '%7Bfoo%3D%22bar%22%7D',
+        start: 1560153109000,
+      });
       expect(labelValues).toEqual(['label1_val1', 'label1_val2']);
     });
 
@@ -247,6 +263,28 @@ describe('Language completion provider', () => {
 
       const nextLabelValues = await provider.fetchLabelValues('testkey');
       expect(requestSpy).toHaveBeenCalledTimes(1);
+      expect(requestSpy).toHaveBeenCalledWith('label/testkey/values', {
+        end: 1560163909000,
+        start: 1560153109000,
+      });
+      expect(nextLabelValues).toEqual(['label1_val1', 'label1_val2']);
+    });
+
+    it('should return cached values when options.streamSelector provided', async () => {
+      const datasource = setup({ testkey: ['label1_val1', 'label1_val2'], label2: [] });
+      const provider = await getLanguageProvider(datasource);
+      const requestSpy = jest.spyOn(provider, 'request');
+      const labelValues = await provider.fetchLabelValues('testkey', { streamSelector: '{foo="bar"}' });
+      expect(requestSpy).toHaveBeenCalledTimes(1);
+      expect(requestSpy).toHaveBeenCalledWith('label/testkey/values', {
+        end: 1560163909000,
+        query: '%7Bfoo%3D%22bar%22%7D',
+        start: 1560153109000,
+      });
+      expect(labelValues).toEqual(['label1_val1', 'label1_val2']);
+
+      const nextLabelValues = await provider.fetchLabelValues('testkey', { streamSelector: '{foo="bar"}' });
+      expect(requestSpy).toHaveBeenCalledTimes(1);
       expect(nextLabelValues).toEqual(['label1_val1', 'label1_val2']);
     });
 
@@ -258,6 +296,19 @@ describe('Language completion provider', () => {
 
       expect(requestSpy).toHaveBeenCalledWith('label/%60%5C%22testkey/values', expect.any(Object));
     });
+
+    it('should encode special characters in options.streamSelector', async () => {
+      const datasource = setup({ '`\\"testkey': ['label1_val1', 'label1_val2'], label2: [] });
+      const provider = await getLanguageProvider(datasource);
+      const requestSpy = jest.spyOn(provider, 'request');
+      await provider.fetchLabelValues('`\\"testkey', { streamSelector: '{foo="\\bar"}' });
+
+      expect(requestSpy).toHaveBeenCalledWith(expect.any(String), {
+        query: '%7Bfoo%3D%22%5Cbar%22%7D',
+        start: expect.any(Number),
+        end: expect.any(Number),
+      });
+    });
   });
 });
 

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

@@ -2,7 +2,7 @@ import { chain, difference } from 'lodash';
 import { LRUCache } from 'lru-cache';
 import Prism, { Grammar } from 'prismjs';
 
-import { dateTime, AbsoluteTimeRange, LanguageProvider, HistoryItem, AbstractQuery } from '@grafana/data';
+import { dateTime, AbsoluteTimeRange, LanguageProvider, HistoryItem, AbstractQuery, KeyValue } from '@grafana/data';
 import { CompletionItem, TypeaheadInput, TypeaheadOutput, CompletionItemGroup } from '@grafana/ui';
 import {
   extractLabelMatchers,
@@ -452,18 +452,29 @@ export default class LokiLanguageProvider extends LanguageProvider {
    * It returns a promise that resolves to an array of strings containing the label values.
    *
    * @param labelName - The name of the label for which you want to retrieve values.
+   * @param options - (Optional) An object containing additional options - currently only stream selector.
+   * @param options.streamSelector - (Optional) The stream selector to filter label values. If not provided, all label values are fetched.
    * @returns A promise containing an array of label values.
    * @throws An error if the fetch operation fails.
    */
-  async fetchLabelValues(labelName: string): Promise<string[]> {
-    const interpolatedKey = encodeURIComponent(this.datasource.interpolateString(labelName));
+  async fetchLabelValues(labelName: string, options?: { streamSelector?: string }): Promise<string[]> {
+    const label = encodeURIComponent(this.datasource.interpolateString(labelName));
+    const streamParam = options?.streamSelector
+      ? encodeURIComponent(this.datasource.interpolateString(options.streamSelector))
+      : undefined;
 
-    const url = `label/${interpolatedKey}/values`;
+    const url = `label/${label}/values`;
     const rangeParams = this.datasource.getTimeRangeParams();
     const { start, end } = rangeParams;
+    const params: KeyValue<string | number> = { start, end };
+    let paramCacheKey = label;
 
-    const cacheKey = this.generateCacheKey(url, start, end, interpolatedKey);
-    const params = { start, end };
+    if (streamParam) {
+      params.query = streamParam;
+      paramCacheKey += streamParam;
+    }
+
+    const cacheKey = this.generateCacheKey(url, start, end, paramCacheKey);
 
     let labelValues = this.labelsCache.get(cacheKey);
     if (!labelValues) {

public/app/plugins/datasource/loki/docs/app_plugin_developer_documentation.md

@@ -58,13 +58,15 @@ The `datasource.languageProvider.fetchLabelValues()` method is designed for fetc
  * It returns a promise that resolves to an array of strings containing the label values.
  *
  * @param labelName - The name of the label for which you want to retrieve values.
+ * @param options - (Optional) An object containing additional options - currently only stream selector.
+ * @param options.streamSelector - (Optional) The stream selector to filter label values. If not provided, all label values are fetched.
  * @returns A promise containing an array of label values.
  * @throws An error if the fetch operation fails.
  */
-async function fetchLabelValues(labelName: string): Promise<string[]>;
+async function fetchLabelValues(labelName: string, options?: { streamSelector?: string }): Promise<string[]>;
 
 /**
- * Example usage:
+ * Example usage without stream selector:
  */
 
 const labelName = 'job';
@@ -74,6 +76,19 @@ try {
 } catch (error) {
   console.error(`Error fetching label values: ${error.message}`);
 }
+
+/**
+ * Example usage with stream selector:
+ */
+
+const labelName = 'job';
+const streamSelector = '{app="grafana"}';
+try {
+  const values = await fetchLabelValues(labelName, { streamSelector });
+  console.log(values);
+} catch (error) {
+  console.error(`Error fetching label values: ${error.message}`);
+}
 ```
 
 ### Fetching Loki labels for a specified selector