Explore: Prevent empty Elasticsearch logs query responses from hiding the logs panel (#40217)

* remove return value from addPreferredVisualisationType

* Elasticsearch: send empty series instead when no data is received for a query

public/app/plugins/datasource/elasticsearch/elastic_response.ts

@@ -489,7 +489,7 @@ export class ElasticResponse {
     return this.processResponseToDataFrames(true, logMessageField, logLevelField);
   }
 
-  processResponseToDataFrames(
+  private processResponseToDataFrames(
     isLogsRequest: boolean,
     logMessageField?: string,
     logLevelField?: string
@@ -501,16 +501,22 @@ export class ElasticResponse {
         throw this.getErrorFromElasticResponse(this.response, response.error);
       }
 
-      if (response.hits && response.hits.hits.length > 0) {
+      if (response.hits) {
         const { propNames, docs } = flattenHits(response.hits.hits);
-        if (docs.length > 0) {
+
-          let series = createEmptyDataFrame(
+        const series = docs.length
+          ? createEmptyDataFrame(
               propNames.map(toNameTypePair(docs)),
-            this.targets[0].timeField!,
               isLogsRequest,
+              this.targets[0].timeField,
               logMessageField,
               logLevelField
-          );
+            )
+          : createEmptyDataFrame([], isLogsRequest);
+
+        if (isLogsRequest) {
+          addPreferredVisualisationType(series, 'logs');
+        }
 
         // Add a row for each document
         for (const doc of docs) {
@@ -552,14 +558,11 @@ export class ElasticResponse {
           }
           series.add(doc);
         }
-          if (isLogsRequest) {
+
-            series = addPreferredVisualisationType(series, 'logs');
-          }
         const target = this.targets[n];
         series.refId = target.refId;
         dataFrame.push(series);
       }
-      }
 
       if (response.aggregations) {
         const aggregations = response.aggregations;
@@ -582,7 +585,7 @@ export class ElasticResponse {
 
           // When log results, show aggregations only in graph. Log fields are then going to be shown in table.
           if (isLogsRequest) {
-            series = addPreferredVisualisationType(series, 'graph');
+            addPreferredVisualisationType(series, 'graph');
           }
 
           series.refId = target.refId;
@@ -690,13 +693,14 @@ const flattenHits = (hits: Doc[]): { docs: Array<Record<string, any>>; propNames
  */
 const createEmptyDataFrame = (
   props: Array<[string, FieldType]>,
-  timeField: string,
   isLogsRequest: boolean,
+  timeField?: string,
   logMessageField?: string,
   logLevelField?: string
 ): MutableDataFrame => {
   const series = new MutableDataFrame({ fields: [] });
 
+  if (timeField) {
     series.addField({
       config: {
         filterable: true,
@@ -704,6 +708,7 @@ const createEmptyDataFrame = (
       name: timeField,
       type: FieldType.time,
     });
+  }
 
   if (logMessageField) {
     series.addField({
@@ -756,8 +761,6 @@ const addPreferredVisualisationType = (series: any, type: PreferredVisualisation
     : (s.meta = {
         preferredVisualisationType: type,
       });
-
-  return s;
 };
 
 const toNameTypePair = (docs: Array<Record<string, any>>) => (propName: string): [string, FieldType] => [

public/app/plugins/datasource/elasticsearch/specs/elastic_response.test.ts

@@ -1432,4 +1432,39 @@ describe('ElasticResponse', () => {
       expect(fields).toContainEqual({ name: 'message', type: 'string' });
     });
   });
+
+  describe('logs query with empty response', () => {
+    const targets: ElasticsearchQuery[] = [
+      {
+        refId: 'A',
+        metrics: [{ type: 'logs', id: '2' }],
+        bucketAggs: [{ type: 'date_histogram', settings: { interval: 'auto' }, id: '1' }],
+        key: 'Q-1561369883389-0.7611823271062786-0',
+        query: 'hello AND message',
+        timeField: '@timestamp',
+      },
+    ];
+    const response = {
+      responses: [
+        {
+          hits: { hits: [] },
+          aggregations: {
+            '1': {
+              buckets: [
+                { key_as_string: '1633676760000', key: 1633676760000, doc_count: 0 },
+                { key_as_string: '1633676770000', key: 1633676770000, doc_count: 0 },
+                { key_as_string: '1633676780000', key: 1633676780000, doc_count: 0 },
+              ],
+            },
+          },
+          status: 200,
+        },
+      ],
+    };
+
+    it('should return histogram aggregation and documents', () => {
+      const result = new ElasticResponse(targets, response).getLogs('message', 'level');
+      expect(result.data.length).toBe(2);
+    });
+  });
 });