Loki: Add maxLines option to getParserAndLabelKeys (#77460)

* Loki: Add logsCount option to getParserAndLabelKeys

* Rename logsCount to maxLines

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

@@ -1,7 +1,7 @@
 import { AbstractLabelOperator, DataFrame } from '@grafana/data';
 
 import LanguageProvider from './LanguageProvider';
-import { LokiDatasource } from './datasource';
+import { DEFAULT_MAX_LINES_SAMPLE, LokiDatasource } from './datasource';
 import { createLokiDatasource, createMetadataRequest } from './mocks';
 import {
   extractLogParserFromDataFrame,
@@ -275,6 +275,40 @@ describe('Query imports', () => {
       });
       expect(extractLogParserFromDataFrameMock).not.toHaveBeenCalled();
     });
+
+    it('calls dataSample with correct default maxLines', async () => {
+      jest.spyOn(datasource, 'getDataSamples').mockResolvedValue([]);
+
+      expect(await languageProvider.getParserAndLabelKeys('{place="luna"}')).toEqual({
+        extractedLabelKeys: [],
+        unwrapLabelKeys: [],
+        hasJSON: false,
+        hasLogfmt: false,
+        hasPack: false,
+      });
+      expect(datasource.getDataSamples).toHaveBeenCalledWith({
+        expr: '{place="luna"}',
+        maxLines: DEFAULT_MAX_LINES_SAMPLE,
+        refId: 'data-samples',
+      });
+    });
+
+    it('calls dataSample with correctly set sampleSize', async () => {
+      jest.spyOn(datasource, 'getDataSamples').mockResolvedValue([]);
+
+      expect(await languageProvider.getParserAndLabelKeys('{place="luna"}', { maxLines: 5 })).toEqual({
+        extractedLabelKeys: [],
+        unwrapLabelKeys: [],
+        hasJSON: false,
+        hasLogfmt: false,
+        hasPack: false,
+      });
+      expect(datasource.getDataSamples).toHaveBeenCalledWith({
+        expr: '{place="luna"}',
+        maxLines: 5,
+        refId: 'data-samples',
+      });
+    });
   });
 });
 

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

@@ -4,7 +4,7 @@ import Prism from 'prismjs';
 import { LanguageProvider, AbstractQuery, KeyValue } from '@grafana/data';
 import { extractLabelMatchers, processLabels, toPromLikeExpr } from 'app/plugins/datasource/prometheus/language_utils';
 
-import { LokiDatasource } from './datasource';
+import { DEFAULT_MAX_LINES_SAMPLE, LokiDatasource } from './datasource';
 import {
   extractLabelKeysFromDataFrame,
   extractLogParserFromDataFrame,
@@ -251,11 +251,21 @@ export default class LokiLanguageProvider extends LanguageProvider {
    * - `unwrapLabelKeys`: An array of label keys that can be used for unwrapping log data.
    *
    * @param streamSelector - The selector for the log stream you want to analyze.
+   * @param {Object} [options] - Optional parameters.
+   * @param {number} [options.maxLines] - The number of log lines requested when determining parsers and label keys.
+   * Smaller maxLines is recommended for improved query performance. The default count is 10.
    * @returns A promise containing an object with parser and label key information.
    * @throws An error if the fetch operation fails.
    */
-  async getParserAndLabelKeys(streamSelector: string): Promise<ParserAndLabelKeysResult> {
+  async getParserAndLabelKeys(
-    const series = await this.datasource.getDataSamples({ expr: streamSelector, refId: 'data-samples' });
+    streamSelector: string,
+    options?: { maxLines?: number }
+  ): Promise<ParserAndLabelKeysResult> {
+    const series = await this.datasource.getDataSamples({
+      expr: streamSelector,
+      refId: 'data-samples',
+      maxLines: options?.maxLines || DEFAULT_MAX_LINES_SAMPLE,
+    });
 
     if (!series.length) {
       return { extractedLabelKeys: [], unwrapLabelKeys: [], hasJSON: false, hasLogfmt: false, hasPack: false };

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

@@ -99,6 +99,7 @@ import { LokiVariableSupport } from './variables';
 
 export type RangeQueryOptions = DataQueryRequest<LokiQuery> | AnnotationQueryRequest<LokiQuery>;
 export const DEFAULT_MAX_LINES = 1000;
+export const DEFAULT_MAX_LINES_SAMPLE = 10;
 export const LOKI_ENDPOINT = '/loki/api/v1';
 export const REF_ID_DATA_SAMPLES = 'loki-data-samples';
 export const REF_ID_STARTER_ANNOTATION = 'annotation-';
@@ -761,8 +762,7 @@ export class LokiDatasource
       expr: query.expr,
       queryType: LokiQueryType.Range,
       refId: REF_ID_DATA_SAMPLES,
-      // For samples we limit the request to 10 lines, so queries are small and fast
+      maxLines: query.maxLines || DEFAULT_MAX_LINES_SAMPLE,
-      maxLines: 10,
       supportingQueryType: SupportingQueryType.DataSample,
     };
 

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

@@ -138,10 +138,16 @@ try {
  * - `unwrapLabelKeys`: An array of label keys that can be used for unwrapping log data.
  *
  * @param streamSelector - The selector for the log stream you want to analyze.
+ * @param {Object} [options] - Optional parameters.
+ * @param {number} [options.maxLines] - The number of log lines requested when determining parsers and label keys.
+ * Smaller maxLines is recommended for improved query performance. The default count is 10.
  * @returns A promise containing an object with parser and label key information.
  * @throws An error if the fetch operation fails.
  */
-async function getParserAndLabelKeys(streamSelector: string): Promise<{
+async function getParserAndLabelKeys(
+  streamSelector: string,
+  options?: { maxLines?: number }
+): Promise<{
   extractedLabelKeys: string[];
   hasJSON: boolean;
   hasLogfmt: boolean;
@@ -154,7 +160,7 @@ async function getParserAndLabelKeys(streamSelector: string): Promise<{
  */
 const streamSelector = '{job="grafana"}';
 try {
-  const parserAndLabelKeys = await getParserAndLabelKeys(streamSelector);
+  const parserAndLabelKeys = await getParserAndLabelKeys(streamSelector, { maxLines: 5 });
   console.log(parserAndLabelKeys);
 } catch (error) {
   console.error(`Error fetching parser and label keys: ${error.message}`);