[APM] Show transaction rate per minute on Observability Overview page

x-pack/plugins/apm/public/services/rest/observability.dashboard.test.ts

@@ -60,7 +60,7 @@ describe('Observability dashboard data', () => {
           transactions: {
             type: 'number',
             label: 'Transactions',
-            value: 6,
+            value: 2,
             color: '#6092c0',
           },
         },
@@ -117,5 +117,45 @@ describe('Observability dashboard data', () => {
         },
       });
     });
+    it('returns transaction stat as 0 when y is undefined', async () => {
+      callApmApiMock.mockImplementation(() =>
+        Promise.resolve({
+          serviceCount: 0,
+          transactionCoordinates: [{ x: 1 }, { x: 2 }, { x: 3 }],
+        })
+      );
+      const response = await fetchLandingPageData(
+        {
+          startTime: '1',
+          endTime: '2',
+          bucketSize: '3',
+        },
+        { theme }
+      );
+      expect(response).toEqual({
+        title: 'APM',
+        appLink: '/app/apm',
+        stats: {
+          services: {
+            type: 'number',
+            label: 'Services',
+            value: 0,
+          },
+          transactions: {
+            type: 'number',
+            label: 'Transactions',
+            value: 0,
+            color: '#6092c0',
+          },
+        },
+        series: {
+          transactions: {
+            label: 'Transactions',
+            coordinates: [{ x: 1 }, { x: 2 }, { x: 3 }],
+            color: '#6092c0',
+          },
+        },
+      });
+    });
   });
 });

x-pack/plugins/apm/public/services/rest/observability_dashboard.ts

@@ -5,7 +5,7 @@
  */
 
 import { i18n } from '@kbn/i18n';
-import { sum } from 'lodash';
+import mean from 'lodash.mean';
 // eslint-disable-next-line @kbn/eslint/no-restricted-paths
 import { FetchDataParams } from '../../../../observability/public/data_handler';
 import { ApmFetchDataResponse } from '../../../../observability/public/typings/fetch_data_response';
@@ -47,7 +47,11 @@ export const fetchLandingPageData = async (
           'xpack.apm.observabilityDashboard.stats.transactions',
           { defaultMessage: 'Transactions' }
         ),
-        value: sum(transactionCoordinates.map((coordinates) => coordinates.y)),
+        value: !!transactionCoordinates.length
+          ? mean(
+              transactionCoordinates.map((coordinates) => coordinates.y || 0)
+            )
+          : 0,
         color: theme.euiColorVis1,
       },
     },

x-pack/plugins/apm/server/lib/observability_dashboard/get_transaction_coordinates.ts

@@ -48,10 +48,12 @@ export async function getTransactionCoordinates({
     },
   });
 
+  const deltaAsMinutes = (end - start) / 1000 / 60;
+
   return (
     aggregations?.distribution.buckets.map((bucket) => ({
       x: bucket.key,
-      y: bucket.doc_count,
+      y: bucket.doc_count / deltaAsMinutes,
     })) || []
   );
 }